Lauriane Plouhinec
email: lauriane.plouhinec@outlook.fr

Virginie Neugnot

Mickael Lafond

Jean-Guy Berrin
email: jean-guy.berrin@inrae.fr

Carbohydrate-active enzymes in animal feed

Keywords: CAZymes, filamentous fungi, non-starch polysaccharides, protein meals, performance gains, animal health metabolizable energy AMEn: apparent metabolizable energycorrected for zero nitrogen retention carbohydrate-active enzymes

Considering an ever-growing global population, which hit 8 billion people in the fall of 2022, it is essential to find solutions to avoid the competition between human food and animal feed for croplands.

Agricultural co-products have become important components of the circular economy with their use in animal feed. Their implementation was made possible by the addition of exogenous enzymes in the diet, especially carbohydrate-active enzymes (CAZymes). In this review, we describe the diversity and versatility of microbial CAZymes targeting non-starch polysaccharides to improve the nutritional potential of diets containing cereals and protein meals. We focused our attention on cellulases, hemicellulases, pectinases which were often found to be crucial in vivo. We also highlight the performance and health benefits brought by the exogenous addition of enzymatic cocktails containing CAZymes in the diets of monogastric animals. Taking the example of the well-studied commercial cocktail Rovabio ™ , we discuss the evolution, constraints and future challenges faced by feed enzymes suppliers. We hope that this review will promote the use and development of enzyme solutions for industries to sustainably feed humans in the future.

INTRODUCTION

Considering an ever-growing global population, with a forecast of 10 billion people on Earth by 2050 [START_REF] Hickey | Breeding crops to feed 10 billion[END_REF][START_REF] Lal | Feeding 11 billion on 0.5 billion hectare of area under cereal crops[END_REF], the issue of competition between food and feed arises, and the need for alternative animal feeding solutions increases. As our planet's resources are not inexhaustible, feeding both humans and animals properly will become a challenge. The Food and Agriculture Organization of the United Nations has evaluated food losses to be equivalent to 750 billion USD and 3.3 gigatons of CO2 emissions per year (Food and Agriculture Organization of the United Nations, 2020). Fourteen percent of these losses account for food lost at the early stages of the food chain, including agricultural co-products, generated during the food transformation process.

Over the past decades, the consideration of agricultural co-products has evolved from useless and disposable, to economically valuable [START_REF] Tuck | Valorization of Biomass: Deriving More Value from Waste[END_REF]. Co-products valorization is defined as any industrial processing activities aimed at reusing, recycling or composting agricultural co-products into useful products or energy sources [START_REF] Kabongo | Waste Valorization[END_REF]. This practice is part of the bioeconomy concept, where the "basic building blocks for materials, chemicals and energy are derived from renewable biological sources" [START_REF] Pacheco-Torgal | 1 -Introduction to biobased materials and biotechnologies for eco-efficient construction[END_REF]. Mainstream co-products valorization goes towards biorefineries with the utilization of plant biomass and agricultural co-products for biofuel production through microbial and/or enzymatic transformation [START_REF] Maina | A roadmap towards a circular and sustainable bioeconomy through waste valorization[END_REF][START_REF] Nayak | An overview of the recent trends on the waste valorization techniques for food wastes[END_REF]. However, bioeconomy challenges go beyond biorefinery, as the projected feed global market is expected to grow up to 70% in the coming decade (Fortune Business Insights, 2022). The rising consumer's demand for ethically-and ecologically-friendly livestock production [START_REF] Pozelli Sabio | Consumers' Expectations on Transparency of Sustainable Food Chains[END_REF] represents a considerable opportunity to develop innovative solutions in line with the circular economy prospective.

In addition to cereals, it is common to find co-products such as oilcake and oilseed meals in animal feed because of their high protein content [START_REF] Sarkar | A comprehensive review on oilseed cakes and their potential as a feedstock for integrated biorefinery 12[END_REF][START_REF] Sindhu | Agro-Industrial By-Products as a Potential Source of Livestock Feed[END_REF]. Indeed, animals requireamong other elements -a specific intake of essential amino acids (AA) due to their inability to synthetize them naturally [START_REF] Wu | Dietary requirements of synthesizable amino acids by animals: a paradigm shift in protein nutrition[END_REF]. Part of these requirements are provided by the addition of free AAs in the diet [START_REF] Karau | Amino acids in human and animal nutrition[END_REF], but the majority is ensured by protein meals. Nevertheless, and despite their multiple assets for feed application, some protein meals currently used in feed formulation have downsides. Some of them exhibit low protein digestibility due to the high content of recalcitrant fibers, representing one of the main bottlenecks hampering their implementation into the diet. Digestibility is defined as the potential of a food or feed ingredient to be degraded, absorbed and processed in the digestive tract of animals [START_REF] Welch | CHAPTER 6 -Nutrient Composition and Nutritional Quality of Oats and Comparisons with Other Cereals[END_REF]. A prerequisite for nutrients assimilation is their degradation into absorbable units, upon action of endogenous digestive enzymes or microbial enzymes from the gut microbiota [START_REF] Joye | Protein Digestibility of Cereal Products[END_REF]. In monogastric livestock such as poultry and pigs, endogenous enzymes secreted in the gastrointestinal tract are not sufficient to access and degrade all the components within the feedstuffs to improve nutrients availability [START_REF] Alagawany | The role of exogenous enzymes in promoting growth and improving nutrient digestibility in poultry[END_REF]. Therefore, several ad-hoc enzymatic cocktails, mostly of fungal origin, have been developed to supplement different types of diets enriched in agricultural co-products, in order to improve their digestibility.

This review aims at depicting how enzymes, especially carbohydrate-active enzymes (or CAZymes), bring added value to the cereal-protein meals-based diets, by releasing their full nutritional potential. In this context, we report and discuss performance gains and health benefits for monogastrics. Of note, the present review will not cover the inventory of enzymes developed for other agricultural co-products used in feed (fruit pomaces, brewer's spent grains, etc.) nor the interests of phytase, amylase and protease addition into the diet, as these aspects have already been considered in other reviews [START_REF] Barcelos | Enzymatic potential for the valorization of agro-industrial byproducts[END_REF][START_REF] Cowieson | Exogenous Microbial Amylase in the Diets of Poultry: What do We Know?[END_REF][START_REF] Erdaw | Enhancing the nutritional value of soybeans for poultry through supplementation with new-generation feed enzymes[END_REF][START_REF] Kithama | The Enzymatic Digestion of Pomaces From Some Fruits for Value-Added Feed Applications in Animal Production[END_REF][START_REF] Slominski | Recent advances in research on enzymes for poultry diets[END_REF].

PROTEIN MEALS AS A NUTRIENT SOURCE FOR ANIMAL FEED

Definition of protein meals and evolution of their use

For many years, protein meals (PM) have been used in animal feed, as a protein source to complement a cereal base, mostly wheat and/or corn. PM, which will also be referred to as "oilseed meals", "oilseed cakes" and "protein cakes", are obtained from oleaginous plant, after the industrial process of oil extraction from the seeds. The three major PM used in feed are coming from soybean, rapeseed and sunflower industries [START_REF] Lomascolo | Rapeseed and sunflower meal: a review on biotechnology status and challenges[END_REF][START_REF] Ravindran | Nutrient analysis, metabolizable energy, and digestible amino acids of soybean meals of different origins for broilers[END_REF][START_REF] Stake | Rapeseed, Sunflower, and Soybean Meal Supplementation of Calf Rations1[END_REF].

Concerning animal feed, soybean meal (SBM) is the world leader in terms on production and utilization [START_REF] Ruiz | A review: 100 years of soybean meal[END_REF], compared to rapeseed (RSM) and sunflower (SFM) meals, mostly because of its high protein content, excellent AAs composition and high level of digestibility. In November 2022, the global production of SBM, RSM and SFM reached 260, 45 and 22 million metric tons respectively, representing up to 65% of the global production of these oilseeds [START_REF] Kingsbury | Oilseeds: World Markets and Trade (World Production, Markets, and Trade Report)[END_REF].

Even though the focus of this review is on PM used in animal feed, several alternatives to PM currently exist for monogastrics nutrition [START_REF] Iji | Alternative sources of protein for poultry nutrition[END_REF][START_REF] Jezierny | The use of grain legumes as a protein source in pig nutrition: A review[END_REF] and some of them are mentioned in the review.

From an European point of view, SBM is imported from the United States, Latin America, or India, while RSM and SFM are mainly produced in EU [START_REF] Lannuzel | Improving fiber utilization from rapeseed and sunflower seed meals to substitute soybean meal in pig and chicken diets: A review[END_REF][START_REF] Lomascolo | Rapeseed and sunflower meal: a review on biotechnology status and challenges[END_REF].

Soybeans, rapeseeds and sunflower seeds are mostly produced for their oil, widely used in human food [START_REF] Clemente | Soybean Oil: Genetic Approaches for Modification of Functionality and Total Content[END_REF][START_REF] Guo | A review of phytochemistry, metabolite changes, and medicinal uses of the common sunflower seed and sprouts (Helianthus annuus L.)[END_REF][START_REF] Matthaus | Some rape/canola seed oils: fatty acid composition and tocopherols[END_REF]. Oil being difficult to extract due to the presence of a hull acting as a physical barrier, oilseeds need to go through a whole preparation process before oil extraction. A succession of cracking, dehulling and flaking allows a mechanical weakening of the seed cell walls, which facilitates the oil recovery by solvent extraction [START_REF] Demarco | Overview of the soybean process in the crushing industry[END_REF]. Although more environment-friendly and healthy alternatives are being studied [START_REF] Mat Yusoff | Aqueous enzyme assisted oil extraction from oilseeds and emulsion de-emulsifying methods: A review[END_REF], extraction with hexane remains the most widespread extraction method in the edible oil industry so far. Once the oil has been recovered, residual solvents in oilseed cakes are evaporated by heating [START_REF] Zhang | Preparation and functional properties of protein from heat-denatured soybean meal assisted by steam flash-explosion with dilute acid soaking[END_REF]. Several studies have investigated the impact of this high temperature treatment, commonly called "toasting", on the nutritional quality of PM. It is known that this step allows the inactivation of some heat labile antinutritional factors (ANFs), such as protease inhibitors and lectins in SBM [START_REF] Woyengo | Modulation of feed Intake in pigs and chickens" and "Feed ingredients, additives and technologies for a healthy gut in pigs[END_REF]. ANFs are generally defined as any compound within the diet which can interfere with the intake, availability, or metabolism of nutrients.

However, the toasting of SBM has no effect on heat-stable ANFs, such as polysaccharides and some oligosaccharides [START_REF] Refstie | Lactic acid fermentation eliminates indigestible carbohydrates and antinutritional factors in soybean meal for Atlantic salmon (Salmo salar)[END_REF]. On another note, by studying the impact of toasting time on in vitro protein solubility in RSM, Salazar-Villanea and his colleagues showed the rate of protein hydrolysis was over 2-fold lower when RSM was toasted for 120 minutes, compared to untoasted RSM [START_REF] Salazar-Villanea | Physical and chemical changes of rapeseed meal proteins during toasting and their effects on in vitro digestibility[END_REF]. Further studies from the same research group highlighted that Maillard reaction caused by the heating of RSM, decreased the in vitro digestibility of insoluble proteins [START_REF] Salazar-Villanea | Effects of Toasting Time on Digestive Hydrolysis of Soluble and Insoluble 00-Rapeseed Meal Proteins[END_REF]. Despite the negative impact of the seeds manufacturing process on some nutritional values of protein meals, SBM, RSM and SFM are widely used in animal feed [START_REF] Ruiz | A review: 100 years of soybean meal[END_REF]. Considering that animal feed accounts for about 75% of meat cost [START_REF] Alagawany | The role of exogenous enzymes in promoting growth and improving nutrient digestibility in poultry[END_REF], it is usual for breeders to harness the nutritional value of PM to feed livestock. This nutritional interest lies in both the protein richness of the PM, and the energy source they represent, due to their carbohydrates content [START_REF] Karr-Lilienthal | Chemical and nutritional properties of soybean carbohydrates as related to nonruminants: A review[END_REF].

Protein content and nutritional value of protein meals

The main nutritional benefit of PM is their high crude protein content. Proteins have a wide range of functions, as structural components, metabolic substrates, or actors of the catabolism, like the digestive enzymes for example. Regardless of this function, 20 AAs are used by animals for proteinogenesis [START_REF] Eugenio | Feeding intact proteins, peptides, or free amino acids to monogastric farm animals[END_REF]. Historically, AAs have been classified by nutritionists into two categories : essential AAs (EAA) and non-essential AAs (NEAA), depending on the organism's ability to synthetize them for its own survival [START_REF] Hou | Endogenous Synthesis of Amino Acids Limits Growth, Lactation, and Reproduction in Animals[END_REF]. For poultry, arginine, glycine, histidine, isoleucine, leucine, lysine, methionine, phenylalanine, proline, threonine, tryptophan, and valine have been identified as EAA [START_REF] Wu | Amino acids: metabolism, functions, and nutrition[END_REF]. Therefore, these 12 AAs need to be brought by feed as full proteins, peptides, or free AAs, to properly ensure the protein synthesis metabolic pathway. While free AAs and small peptides can be easily assimilated in the gastrointestinal tract, full proteins need to be hydrolyzed before assimilation [START_REF] Eugenio | Feeding intact proteins, peptides, or free amino acids to monogastric farm animals[END_REF]. Hence, it is common to determine both crude protein digestibility and AAs content when characterizing the nutritive value of PM for feed formulation [START_REF] Friedman | Nutritional Value of Proteins from Different Food Sources[END_REF][START_REF] Goerke | Standardized ileal digestibilities of crude protein, amino acids, and contents of antinutritional factors, mycotoxins, and isoflavones of European soybean meal imports fed to piglets1[END_REF][START_REF] Ravindran | Nutrient analysis, metabolizable energy, and digestible amino acids of soybean meals of different origins for broilers[END_REF]. It is well-known that the crude protein and AAs content of PM can vary depending on the type of seed, cultivar, region of production, storage conditions, and manufacturing process of oil extraction [START_REF] Newkirk | The effects of toasting canola meal on body weight, feed conversion efficiency, and mortality in broiler chickens[END_REF]. Near-infrared reflectance spectroscopy analysis of the most important protein-rich feed ingredients showed differences of EAAs contents between SBM, RSM and SFM [START_REF] Fontaine | Near-Infrared Reflectance Spectroscopy Enables the Fast and Accurate Prediction of the Essential Amino Acid Contents in Soy, Rapeseed Meal, Sunflower Meal, Peas, Fishmeal, Meat Meal Products, and Poultry Meal[END_REF]. This study revealed that SBM contains on average more arginine and leucine than RSM and SFM, but less methionine. Furthermore, an evaluation of 55 samples of SBM from the United States, Argentina, Brazil and India highlighted significant differences in the nutritional values [START_REF] Ravindran | Nutrient analysis, metabolizable energy, and digestible amino acids of soybean meals of different origins for broilers[END_REF]. The digestible crude protein contents measured in the samples varied from 37 to 40%. To corroborate these observations, an evaluation of 159 Brazilian samples of soybeans also revealed significant nutritional differences depending of the sampling area [START_REF] Goldflus | Amino acid content of soybean samples collected in different Brazilian states: harvest 2003/2004[END_REF]. For the purpose of reducing feed costs and ammonia excretion in environment, produced by dietary protein hydrolysis in gut, many researches focused on the effect of low-crude protein diets on poultry performances [START_REF] Brink | Reduction of dietary crude protein and feed form: Impact on broiler litter quality, ammonia concentrations, excreta composition, performance, welfare, and meat quality[END_REF][START_REF] Kriseldi | Effects of feeding reduced crude protein diets on growth performance, nitrogen excretion, and plasma uric acid concentration of broiler chicks during the starter period2 2Mention of trade names or commercial products in this publication is solely for the purpose of providing specific information and does not imply recommendation or endorsement by Auburn University[END_REF][START_REF] Saleh | Effect of Low Protein Diets with Amino Acids Supplementation on Growth Performance, Carcass Traits, Blood Parameters and Muscle Amino Acids Profile in Broiler Chickens under High Ambient Temperature[END_REF][START_REF] Sigolo | Effect of a low crude protein diet supplemented with different levels of threonine on growth performance, carcass traits, blood parameters, and immune responses of growing broilers[END_REF]. These studies highlighted that the AA levels of PM in diet is a critical parameter determining broilers performances, and its reduction in feedstuffs can be balanced with the addition of pure and free AAs like threonine, lysine, or methionine.

Recording animal performance and health parameters to improve feed formulation

Among the most frequent performance parameters used in poultry production, we find body weight gain (BWG), feed intake (FI) and feed conversion ratio (FCR). While BWG and FI parameters are easily understandable, the less obvious FCR is an indicator of breeding economic performance, defined as the feed requirement per unit of BWG. In a more clear-cut way, this ratio compares the amount of feed ingested by a breeding animal to the amount of its outputs, i.e., meat and/or eggs for poultry [START_REF] Wenk | Energetic aspects of feed conversion in growing pigs[END_REF]. Regarding health and welfare, several parameters have been reported.

Historically, the evaluation of foot pad dermatitis prevailed because it is a visual and easy-to-assess parameter [START_REF] Shepherd | Footpad dermatitis in poultry[END_REF]. Nowadays, as a consequence of technological and analytical advances, other broilers chickens health indicators have emerged, such as the analysis of gut microbiomes by 16S rRNA metabarcoding and the measurement of blood or intestinal markers, like the short-chain fatty acids (SCFA) amount (Yacoubi et al., 2018b).

Other parameters are also reported when carrying in vivo trials, including the Apparent Metabolizable Energy (AME). Used since the mid 1950's [START_REF] Hill | Comparison of Metabolizable Energy and Productive Energy Determinations with Growing Chicks[END_REF], AME refers to the difference between the dietary Gross Energy (GE) ingested, and the residual GE in birds' excreta. This parameter is widely accepted and applied in feed formulation, as it is simple to measure and does not require animal sacrifice [START_REF] Khalil | Influence of feed form on the apparent metabolisable energy of feed ingredients for broiler chickens[END_REF]. Once calculated, AME can be corrected for zero nitrogen retention, giving another indicator, called AMEn. This correction assumes that N-containing non-dietary compounds present in excreta, like uric acid, can bias the measurement of diet AME.

Nevertheless, the relevance of using AMEn compared to AME, in PM-based diets, has been recently discussed from an animal production cost point of view. Indeed, it has been shown that using AMEn instead of AME, values for feed formulation could result in an undervaluation of high-quality protein sources, hence an increase of feed costs [START_REF] Abdollahi | Application of Apparent Metabolizable Energy versus Nitrogen-Corrected Apparent Metabolizable Energy in Poultry Feed Formulations: A Continuing Conundrum[END_REF]. The U.S. National Research Council (NRC) defined the nutrient requirements for poultry almost 30 years ago (National Research Council, 1994). While farming methods have changed, and the productive potential of modern broilers chickens have increased, the definition of poultry's nutrients requirements has not changed much since then.

Although some manufacturers use other reference systems, the vast majority of feedstuffs formulated nowadays are based on these requirements, leading some scientists to question the validity of NRC statements [START_REF] Applegate | Nutrient requirements of poultry publication: History and need for an update[END_REF]. In addition to this, new approaches for feed formulation are rising, among which the diets formulation based on their impact on gut health and/or their indigestible components [START_REF] Choct | Managing gut health through nutrition[END_REF][START_REF] Vieira | Formulating poultry diets based on their indigestible components[END_REF]. Indeed, although rich in assimilable nutrients, part of the nutritive value of PM is entrapped in polysaccharidic complexes. This entrapment has been illustrated in SBM using scanning electron microscopy, and is explained by the concentration of carbohydrates content in PM during oil extraction process [START_REF] Xing | Protein enrichment of defatted soybean flour by fine milling and electrostatic separation[END_REF]. Whether the seed processing is mechanical or solvent-based, it leads to fiber tightening around protein bodies, which are the main protein storage in oilseeds like soybeans [START_REF] Medic | Current Knowledge in Soybean Composition[END_REF]. Thus, carbohydrates content in PM is both an issue and an opportunity since their degradation into absorbable units in the gut represents a significant source of energy and a potential leverage for performance.

The ambivalence of the carbohydrates content of protein meals

The carbohydrates content of PM is close to the composition of plant cell wall (PCW), as they are mostly composed of non-starch polysaccharides (NSPs) [START_REF] Bach Knudsen | The nutritional significance of "dietary fibre" analysis[END_REF][START_REF] Lovegrove | Role of polysaccharides in food, digestion, and health[END_REF]. Also referred to as "fiber", when it comes to food and feed, the term NSP was first introduced in 1953, to designate non-digestible constituents constituting the PCW [START_REF] Hipsley | Dietary "Fibre" and Pregnancy Toxaemia[END_REF]. Ever since, many different entities of fibers have been identified, depending on their chemical properties, leading to a complexification and a multiplication of the parameters determining feedstuffs formulation (M Choct, 2015). NSPs are classified into three main categories, i.e., cellulose, hemicelluloses, and pectins (Figure 1 ; [START_REF] Choct | Feed non-starch polysaccharides for monogastric animals: Classification and function[END_REF][START_REF] Cosgrove | Comparative structure and biomechanics of plant primary and secondary cell walls[END_REF][START_REF] Cosgrove | Growth of the plant cell wall[END_REF]. [START_REF] Agger | Enzymatic Xylose Release from Pretreated Corn Bran Arabinoxylan: Differential Effects of Deacetylation and Deferuloylation on Insoluble and Soluble Substrate Fractions[END_REF][START_REF] Attia | Recent structural insights into the enzymology of the ubiquitous plant cell wall glycan xyloglucan[END_REF][START_REF] Déjean | Adaptation of Syntenic Xyloglucan Utilization Loci of Human Gut Bacteroidetes to Polysaccharide Side Chain Diversity[END_REF][START_REF] Luis | Dietary pectic glycans are degraded by coordinated enzyme pathways in human colonic Bacteroides[END_REF][START_REF] Ndeh | Complex pectin metabolism by gut bacteria reveals novel catalytic functions[END_REF][START_REF] Ralet | Sugar beet (Beta vulgaris) pectins are covalently cross-linked through diferulic bridges in the cell wall[END_REF][START_REF] Rogowski | Glycan complexity dictates microbial resource allocation in the large intestine[END_REF][START_REF] Saulnier | Ferulic acid and diferulic acids as components of sugar-beet pectins and maize bran heteroxylans[END_REF][START_REF] Von Freiesleben | Crystal structure and substrate interactions of an unusual fungal non-CBM carrying GH26 endo-β-mannanase from Yunnania penicillata[END_REF] Cellulose is an unbranched polymer of D-glucose residues linked in β(1,4), able to form crystalline microfibrils highly resistant to enzymatic degradation [START_REF] Cosgrove | Growth of the plant cell wall[END_REF]. In vivo, this polysaccharide brings strength to the PCW, protecting it from parasites and pathogens, thanks to its recalcitrance and its role in plant immunity [START_REF] Trouvelot | Carbohydrates in plant immunity and plant protection: roles and potential application as foliar sprays[END_REF].

Hemicelluloses are a complex group of plant heteropolysaccharides, mainly composed of xyloglucans, (arabino)xylans and (galacto)mannans [START_REF] Arzami | Valorization of cereal by-product hemicelluloses: Fractionation and purity considerations[END_REF][START_REF] Karr-Lilienthal | Chemical and nutritional properties of soybean carbohydrates as related to nonruminants: A review[END_REF].

Among the most common hemicelluloses are xyloglucan, made of D-xylose moieties on a β-(1,4)-Dglucan backbone [START_REF] Park | Xyloglucan and its Interactions with Other Components of the Growing Cell Wall[END_REF], and arabinoxylan, constituted by L-arabinose moieties on a β-(1,4)-D-xylan backbone [START_REF] Mikkonen | Arabinoxylan structure affects the reinforcement of films by microfibrillated cellulose[END_REF].

Pectin is the most intricate heteropolymer of the plant kingdom, its backbone being mainly composed of D-galacturonic acids (D-GalA), instead of neutral sugars like the others plant polysaccharides. Adding to this backbone originality, the complexity of pectin is based on a large number and diversity of ramifications, whose nature determines the subtype of pectin [START_REF] Voragen | Pectin, a versatile polysaccharide present in plant cell walls[END_REF]. Starting with the simplest one, homogalacturonan, a polymer of methyl and acetyl esterified D-GalA linked in α-(1,4) which generally constitutes 60 to 65% of total pectin in planta [START_REF] Venkatanagaraju | Extraction and Purification of Pectin from Agro-Industrial Wastes, Pectins -Extraction[END_REF]. The xylosylated form of homogalacturonan is called xylogalacturonan and is considered as a minor component of pectin, like the rhamnogalacturonan-II (RG-II), a highly and diversely substituted polymer of L-rhamnose (L-Rha) and D-GalA [START_REF] Harholt | Biosynthesis of Pectin[END_REF][START_REF] Mohnen | Pectin structure and biosynthesis[END_REF][START_REF] Ndeh | Complex pectin metabolism by gut bacteria reveals novel catalytic functions[END_REF]. On the other hand, rhamnogalacturonan-I (RG-I) represent up to 85% of pectic polysaccharides, depending on plant origin and extraction process. RG-I backbone is constituted of repeating units of D-GalA and L-Rha residues, linked alternatively in α-(1,4) or α-(1,2). Many side chains containing neutral sugars are bond to this backbone, among which arabinans, galactans and/or arabinogalactans [START_REF] Kaczmarska | Structure and functionality of Rhamnogalacturonan I in the cell wall and in solution: A review[END_REF][START_REF] Luis | Dietary pectic glycans are degraded by coordinated enzyme pathways in human colonic Bacteroides[END_REF]. In an attempt to characterize soluble polysaccharides from soybean by enzymatic degradation, the presence of xylose, fucose and glucose was demonstrated in RG-I, in a cumulative proportion of 5.3%, illustrating the wide diversity of RG-I composition [START_REF] Nakamura | Analysis of structural components and molecular construction of soybean soluble polysaccharides by stepwise enzymatic degradation[END_REF].

The structures of NSPs in oilseeds have been poorly investigated. Most of the information currently available emanate from the characterization of cereals such as wheat, barley, corn and rye [START_REF] Ralet | Raw and extruded fibre from pea hulls. Part II: Structural study of the water-soluble polysaccharides[END_REF][START_REF] Saulnier | 2.20 -Plant Cell Wall Polysaccharides in Storage Organs: Xylans (Food Applications)[END_REF]. The main NSPs found in protein-rich seeds are pectin polysaccharides, xyloglucans, gluco-and galactomannans, which vary in structure and composition between the hull and the cotyledon [START_REF] Knudsen | Fiber and nonstarch polysaccharide content and variation in common crops used in broiler diets[END_REF][START_REF] Navarro | Structures and characteristics of carbohydrates in diets fed to pigs: a review[END_REF]. Beyond polysaccharides, soybeans have the highest galacto-oligosaccharides content compared to other oilseeds, namely raffinose, stachyose and verbascose, which can represent up to 7% of the dry matter [START_REF] Cabrera-Orozco | Soybean: Non-Nutritional Factors and Their Biological Functionality[END_REF][START_REF] Middelbos | 9 -Soybean Carbohydrates[END_REF]. These oligosaccharides are often considered to be ANFs as they can interfere with the digestion of other nutrients, by promoting anaerobic fermentation in the hindgut [START_REF] Martínez-Villaluenga | Alpha-galactosides: antinutritional factors or functional ingredients?[END_REF]. Overall, NSPs can represent up to 75% of plant components [START_REF] Choct | Feed non-starch polysaccharides for monogastric animals: Classification and function[END_REF]. The characterization of oilseeds meals has revealed that SFM can contain up to twice more total NSPs than SBM, mainly due to its richness in cellulose [START_REF] Lannuzel | Improving fiber utilization from rapeseed and sunflower seed meals to substitute soybean meal in pig and chicken diets: A review[END_REF]. NSPs content is 50% higher in SBM than in wheat [START_REF] Bao | Dietary NSP nutrition and intestinal immune system for broiler chickens[END_REF], while barley presents a NSPs content of about 17-20% [START_REF] Nguyen | Dietary Soluble Non-Starch Polysaccharide Level Influences Performance, Nutrient Utilisation and Disappearance of Non-Starch Polysaccharides in Broiler Chickens[END_REF] and RSM contains 20 to 40% (de [START_REF] De Vries | Effects of processing technologies and pectolytic enzymes on degradability of nonstarch polysaccharides from rapeseed meal in broilers[END_REF]. NSPs content was found to represent more than 50% of the enzymatically deproteinated, waterinsoluble cell wall material of SFM after chemical extraction [START_REF] Dusterhoft | Non-starch polysaccharides from sunflower (Helianthus annuus) meal and palm kernel (Elaeis guineenis) meal--preparation of cell wall material and extraction of polysaccharide fractions[END_REF]. Such differences can be explained by a concentration of fiber content induced during the oil extraction process [START_REF] Karr-Lilienthal | Chemical and nutritional properties of soybean carbohydrates as related to nonruminants: A review[END_REF]. In a similar way, oilseed meals contain sugar monomers and oligomers, which are released from polysaccharides during the oil extraction process. In PM, the proportions and structure of NSPs also vary according to the nature of oilseed, as well as the manufacturing process [START_REF] Bell | Nutrients and toxicants in rapeseed meal: a review[END_REF][START_REF] Fischer | Limiting factors for the enzymatic accessibility of soybean protein[END_REF][START_REF] Karr-Lilienthal | Chemical and nutritional properties of soybean carbohydrates as related to nonruminants: A review[END_REF][START_REF] Naczk | Carbohydrates of Canola and Rapeseed[END_REF]. Indeed, in a review on RG-I structure in PCW and in solution, Kaczmarska and colleagues emphasized that major structural modifications could occur during the storage of pectin-containing substances [START_REF] Kaczmarska | Structure and functionality of Rhamnogalacturonan I in the cell wall and in solution: A review[END_REF]. Likewise, the carbohydrate content of SBM can vary depending on the geographic origin of the product [START_REF] Karr-Lilienthal | Chemical and nutritional properties of soybean carbohydrates as related to nonruminants: A review[END_REF].

In addition, depending on their chemical characteristics, NSPs can be either soluble (sNSP) or insoluble (iNSP) in animal gut [START_REF] Musigwa | Multi-carbohydrase effects on energy utilization depend on soluble non-starch polysaccharides-to-total non-starch polysaccharides in broiler diets[END_REF]. Their content in oilseeds differs according to the seed type and maturation stage [START_REF] Deng | Effects of different types of non-starch polysaccharides on growth, digestive enzyme activity, intestinal barrier function and antioxidant activity of rainbow trout (Oncorhynchus mykiss)[END_REF]. A characterization of SBM and RSM by gas-liquid chromatography showed SBM contains more soluble than insoluble non-cellulosic polysaccharides, while RSM exhibits over twice more insoluble non-cellulosic polysaccharides than soluble ones [START_REF] Knudsen | Carbohydrate and lignin contents of plant materials used in animal feeding[END_REF]. Either way, both sNSP and iNSP are highly resistant to digestive enzymes in broilers, and their antinutritional effects are conditioned by different mechanisms. While sNSP are responsible for a higher digesta viscosity, interfering with the digestibility of the diet, iNSP operate as a "cage" for nutrients, by creating a physical barrier to the digestive enzymes secreted for their proper assimilation [START_REF] Aulrich | Studies on the mode of action of non-starch-polysaccharides (NSP)-degrading enzymes in vitro[END_REF][START_REF] Musigwa | Multi-carbohydrase effects on energy utilization depend on soluble non-starch polysaccharides-to-total non-starch polysaccharides in broiler diets[END_REF]. Gaining access to these nutrients requires a prior polysaccharide deconstruction step, involving a multitude of enzymatic activities, due to the high diversity of PM's carbohydrates. Some of these enzymes are secreted by the animal itself (i.e., endogenous), however, the basal digestive system of monogastric animals can only digest 75% of the diet [START_REF] Ojha | Chapter 7 -Enzymes in the Animal Feed Industry[END_REF], due to the lack of enzymes active on recalcitrant NSPs. Some CAZymes are also secreted in the gut by the microbiota of monogastrics [START_REF] Glendinning | Assembly of hundreds of novel bacterial genomes from the chicken caecum[END_REF][START_REF] Kaoutari | The abundance and variety of carbohydrate-active enzymes in the human gut microbiota[END_REF], generating SCFAs which can inhibit the proliferation of the pathogenic microbiota and contribute to the immunity of the host [START_REF] Liu | Biological Function of Short-Chain Fatty Acids and Its Regulation on Intestinal Health of Poultry[END_REF]. Part of the degradation products of NSPs is metabolized by the microbiota, reducing the amount of nutrients absorbed by the animal. Achieving a more complete degradation of NSPs to improve their intestinal absorption is therefore possible through the addition of exogenous enzymes [START_REF] Kim | The flow of non-starch polysaccharides along the gastrointestinal tract of broiler chickens fed either a wheat-or maizebased diet[END_REF]. The following section will depict how enzymatic cocktails containing CAZymes, more specifically glycoside hydrolases (GHs), are essential in animal feed to ensure a proper nutrient assimilation in the digestive tract.

THE ROLE OF CAZYMES TO IMPROVE NUTRIENTS DIGESTIBILTY IN FEED

Definition and diversity of CAZymes

Carbohydrate-active enzymes, commonly known as CAZymes or carbohydrases, are classified within the CAZy database (available at www.cazy.org) as "responsible for the synthesis, modifications and breakdown of glycoconjugates, oligo-and polysaccharides". Based on their protein sequence similarities and 3D structure, CAZymes are sorted into five classes: glycoside hydrolases (GH), glycotransferases (GT), polysaccharide lyases (PL), carbohydrate esterases (CE) and auxiliary activities (AA). The CAZy database also includes the carbohydrate-binding modules (CBM), secondary non-catalytic domains commonly associated with the catalytic modules to enhance the binding of CAZymes to their substrates. As of April 2023, the database encompasses 180 GH, 116 GT, 42 PL, 20 CE, 17 AA, and 97 CBM families. The database is constantly updated with the new (meta)genomes sequenced and the new enzymes discovered by the scientific community [START_REF] Drula | The carbohydrate-active enzyme database: functions and literature[END_REF][START_REF] Cazypedia | Ten years of CAZypedia: a living encyclopedia of carbohydrateactive enzymes[END_REF].

When talking about enzymes active on NSPs, it is common to hear the term "NSPases", which actually encompasses a large number of enzymes depending on the polymer targeted (Figure 2 ; Singh and Kim, 2021). Cellulose-degrading enzymes are often referred by the generic name "cellulases".

Cellulases designate several CAZy families, some having an hydrolytic activity, like the GH7 β-glucanases, others exhibiting an oxidative cleavage activity, like the lytic polysaccharide monooxygenases (or LPMOs) from AA9 family [START_REF] Vandhana | On the expansion of biological functions of lytic polysaccharide monooxygenases[END_REF]. Hemicellulosedeconstructing enzymes are more commonly identified by the type of hemicellulose for which they are specific, like xylanases [START_REF] Berrin | Factors affecting xylanase functionality in the degradation of arabinoxylans[END_REF][START_REF] Paës | GH11 xylanases: Structure/function/properties relationships and applications[END_REF] and arabinofuranosidases [START_REF] Wilkens | GH62 arabinofuranosidases: Structure, function and applications[END_REF] which are both active on arabinoxylan. Pectin being even more heterogenous, the unspecific but often-used term "pectinase" refers to many different activities, such as polygalacturonases from GH28 family, pectin lyases from PL1 family or rhamnogalacturonases from GH78 family [START_REF] Bonnin | Pectin-modifying enzymes and pectin-derived materials: applications and impacts[END_REF][START_REF] Hage | Evolution of Fungal Carbohydrate-Active Enzyme Portfolios and Adaptation to Plant Cell-Wall Polymers[END_REF]. The diversity of CAZymes also resides in their mode of action, i.e., exo-active when they target the extremities of the polymer or endo-active when they act within the chains. Beyond the intrinsic composition of polysaccharides, their degrees of polymerization, substitution, and supramolecular arrangement are other important parameters affecting CAZyme activity and specificity. Due to their wide portfolio of substrates and activities, using CAZymes for PM valorization in animal feed drives a "green" and sustainable transformation of recalcitrant plant polymers [START_REF] Bourlieu | Enzymes to unravel bioproducts architecture[END_REF]. A wide array of CAZymes are secreted by micro-organisms (mainly bacteria and fungi), some of them being naturally present in the chicken microbiota. A recent genome-resolved metagenomics analysis of the chicken gut microbiome highlighted the predominance of bacterial GHs active on starch and cellulose (Segura- Wang et al., 2021). However, hemicellulases and pectinases seem less represented. Interestingly, recent studies have been initiated to characterize the intestinal mycobiota in broiler chickens, although the CAZymes at play have not been studied in details [START_REF] Davies | Temporal dynamics of the chicken mycobiome[END_REF][START_REF] Robinson | Biogeography, succession, and origin of the chicken intestinal mycobiome[END_REF][START_REF] Robinson | Chicken Intestinal Mycobiome: Initial Characterization and Its Response to Bacitracin Methylene Disalicylate[END_REF]. Nevertheless, it is generally acknowledged that the absorption of nutrients occurs mainly in the small intestine and most of the microbiota is found in the distal compartment where nutrient absorption is poor. Therefore, to breakdown anti-nutritional factors and reduce the viscosity of the diet, the action of enzymes must occur early in the digestive tract.

Feed additives companies have elaborated strategies based on the development of microbial enzymatic cocktails and blends [START_REF] Giovannoni | Industrial Use of Cell Wall Degrading Enzymes: The Fine Line Between Production Strategy and Economic Feasibility[END_REF][START_REF] Okpara | Microbial Enzymes and Their Applications in Food Industry: A Mini-Review[END_REF]. Enzymatic cocktail refers to a set of enzymes produced by a single organism [START_REF] Filiatrault-Chastel | From fungal secretomes to enzymes cocktails: The path forward to bioeconomy[END_REF], genetically modified or not, while enzymatic blend refers to a mixture of enzymatic products from different sources. As previously mentioned, the inability of monogastric animals to fully hydrolyze NSPs with their own digestive enzymes can be balanced by the addition of exogenous enzymesalone, in cocktails or in blendsto the feed. Historically, xylanases and glucanases are the most widespread enzymatic activities claimed in commercial cocktails (Table 1, non-exhaustive list), and they have been commercialized as feed additives for over 30 years (Bedford and Partridge, 2010). Nevertheless, complementary activities such as arabinofuranosidases, mannanases, galactosidases or pectinases are needed and they are multiplying on the feed additives market [START_REF] Cozannet | Next-generation non-starch polysaccharide-degrading, multi-carbohydrase complex rich in xylanase and arabinofuranosidase to enhance broiler feed digestibility[END_REF][START_REF] Giovannoni | Industrial Use of Cell Wall Degrading Enzymes: The Fine Line Between Production Strategy and Economic Feasibility[END_REF]Mathlouthi et al., 2002b;[START_REF] Wilkens | GH62 arabinofuranosidases: Structure, function and applications[END_REF].

Fungal CAZymes for NSPs degradation in feed: the example of Rovabio™ cocktails

Most of the industrial enzymatic products currently available on the market have a fungal origin [START_REF] Østergaard | Industrial Applications of Fungal Enzymes[END_REF]. This prevalence coincides with a better understanding of fungal enzymatic diversity [START_REF] Hage | Evolution of Fungal Carbohydrate-Active Enzyme Portfolios and Adaptation to Plant Cell-Wall Polymers[END_REF], and a rising awareness of the industrial potential of fungi to answer bioeconomy and mankind's challenges [START_REF] El-Gendi | A Comprehensive Insight into Fungal Enzymes: Structure, Classification, and Their Role in Mankind's Challenges[END_REF][START_REF] Filiatrault-Chastel | From fungal secretomes to enzymes cocktails: The path forward to bioeconomy[END_REF][START_REF] Meyer | Growing a circular economy with fungal biotechnology: a white paper[END_REF]. Being natural plant degraders in the environment, filamentous fungi possess a wide enzymatic portfolio with many good candidates for the deconstruction of NSPs in animal feed.

As exposed in Kutlu and colleagues work, the addition in a low-nutrient diet of a multi-enzyme cocktail (i.e., secretome) secreted by the fungus Talaromyces versatilis, gave similar performance results as the ones obtained with the nutrients-adequate diet for broilers [START_REF] Kutlu | Effect of Multi-enzyme Produced By a Single Fungus on Growth Performance and Some Carcass Parameters of Broiler Chicks Fed on Maize-Soya Based Diets[END_REF]. Besides, it was previously demonstrated that the effect of this enzymatic cocktail is closely linked to the NSPs content of the diet, better animal performances being correlated with higher levels of arabinoxylans [START_REF] Cozannet | Dietary Energy and Amino Acid Enhancement From a Multi-enzyme Preparation[END_REF][START_REF] Cozannet | Next-generation non-starch polysaccharide-degrading, multi-carbohydrase complex rich in xylanase and arabinofuranosidase to enhance broiler feed digestibility[END_REF]. The main advantage of fungal secretomes lies in their CAZymes richness and diversity, which can be shaped by the substrate used for fungi cultivation [START_REF] Hage | Evolution of Fungal Carbohydrate-Active Enzyme Portfolios and Adaptation to Plant Cell-Wall Polymers[END_REF][START_REF] Haltrich | Production of fungal xylanases[END_REF][START_REF] Levin | Copper induction of lignin-modifying enzymes in the white-rot fungus Trametes trogii[END_REF][START_REF] Llanos | Carbon sources and XlnR-dependent transcriptional landscape of CAZymes in the industrial fungus Talaromyces versatilis: when exception seems to be the rule[END_REF][START_REF] Riou | Production of Cell Wall-Degrading Enzymes by the Phytopathogenic Fungus Sclerotinia sclerotiorum[END_REF]. Multiple proteomics analysis of the secretome from Talaromyces versatilis (formerly Penicillium funiculosum) highlighted more than 50 different enzymatic activities, constituting the commercial cocktails of Rovabio™ range produced by Adisseo ® (Guais et al., 2008). Among them are the claimed GH5 glucanases and GH11

xylanases, but also GH53 galactanases, GH62 arabinofuranosidases, GH28 polygalacturonases, CE5

xylan esterases, or GH47 mannosidases. The in vitro characterization of some of these enzymes (Table 2), mostly xylanases [START_REF] Berrin | Substrate and product hydrolysis specificity in family 11 glycoside hydrolases: an analysis of Penicillium funiculosum and Penicillium griseofulvum xylanases[END_REF][START_REF] Driss | Functional characterization of Penicillium occitanis Pol6 and Penicillium funiculosum GH11 xylanases[END_REF][START_REF] Lafond | Four GH11 xylanases from the xylanolytic fungus Talaromyces versatilis act differently on (arabino)xylans[END_REF]Lafond et al., 2011) and arabinofuranosidases [START_REF] De La Mare | Molecular and biochemical characterization of three GH62 α-l-arabinofuranosidases from the soil deuteromycete Penicillium funiculosum[END_REF][START_REF] Guais | Characterization of the family GH54 α-l-arabinofuranosidases in Penicillium funiculosum, including a novel protein bearing a cellulose-binding domain[END_REF], led to the optimization of Rovabio™ Excel into Rovabio™ Advance, by an overexpression of arabinoxylan-degrading enzymes transcription factors in Talaromyces versatilis [START_REF] Guais | Genomic characterization and gene regulation optimization to further improve an enzymatic mix used as feed additive[END_REF].

To go further in improving, Grandmontagne and colleagues studied in 2021 the supplementation of Rovabio™ Advance by several experimental fungal secretomes, to enhance the in vitro digestibility of SBM [START_REF] Grandmontagne | The Secretomes of Aspergillus japonicus and Aspergillus terreus Supplement the Rovabio® Enzyme Cocktail for the Degradation of Soybean Meal for Animal Feed[END_REF]. Enzymes secreted by Aspergillus japonicus (BRFM 405 strain) and Aspergillus terreus (BRFM 111 strain) increased SBM solubilization by 1.8-and 2.8-fold respectively, when compared to Rovabio™ Advance alone. It might be relevant and interesting to go deeper on this research, by trying to identify which activities within these secretomes are responsible for this synergy with the main activities found in Rovabio™ Advance, i.e., endo-xylanase and endo-glucanase. Although its purpose is the feeding of ruminants, a 2020 study seems to corroborate the conclusions made by Grandmontagne and colleagues, regarding the application of A. terreus enzymes for enhanced feed degradability [START_REF] Azzaz | Pectinase Production Optimization for Improving Dairy Animal's Diets Degradation[END_REF].

As shown in Table 2, many enzymes characterization works have been reported for the Rovabio™ cocktails, leading to the continuous increase of their efficiency. Gaining knowledge on the structure and mode of action of enzymes is therefore a relevant avenue for cocktail improvement. For instance, the recombinant xylanase from Clostridium thermocellum (Xyn11A) was 5 to 6% more efficient on cereal-based diets when comprising a CBM6 [START_REF] Fontes | A family 6 carbohydrate-binding module potentiates the efficiency of a recombinant xylanase used to supplement cereal-based diets for poultry[END_REF]. It was demonstrated that the Xyn11A-CBM6 gave better BWG results than both the Xyn11A catalytic module and the enzyme mixture Roxazyme™ G in wheat-based diets. Interestingly, by studying the enzyme structure in different compartments of the digestive tract, it turned out that the Xyn11A-CBM6 was truncated into its single domain in the duodenum. With this observation, it was concluded that the performance improvements highlighted are due to an action of the xylanase prior to the duodenum. Animal gut being a hostile environment, additional parameters must be considered when designing enzymatic cocktails for feed, such as the extreme pH in the stomach and the digestive army of inhibitors and proteases [START_REF] Ao | In vitro evaluation of feed-grade enzyme activity at pH levels simulating various parts of the avian digestive tract[END_REF][START_REF] Svihus | Effect of digestive tract conditions, feed processing and ingredients on response to NSP enzymes[END_REF]. Most microbial NSP-degrading CAZymes have an optimum pH around 4 to 6 [START_REF] Ravindran | Feed enzymes: The science, practice, and metabolic realities[END_REF][START_REF] Svihus | Effect of digestive tract conditions, feed processing and ingredients on response to NSP enzymes[END_REF], higher than the acidic gastric pH of chickens [START_REF] Farner | The Hydrogen Ion Concentration in Avian Digestive Tracts[END_REF]. Nevertheless, in vitro characterization of the Rovabio™ Excel cocktail revealed that it displays glucanases, cellobiohydrolases and glucosidases active over a broad range of pH (from 2.0 to 8.0), as well as an optimal temperature above 40°C [START_REF] Karboune | Characterization of Selected Cellulolytic Activities of Multi-enzymatic Complex System from Penicillium funiculosum[END_REF]. These observations indicate this fungal enzymatic cocktail is suitable for the degradation of NSPs such as cellulose in the proventriculus of birds, where the pH is close to 4 depending on the diet [START_REF] Farner | The Hydrogen Ion Concentration in Avian Digestive Tracts[END_REF][START_REF] Gabriel | Differences in the digestive tract characteristics of broiler chickens fed on complete pelleted diet or on whole wheat added to pelleted protein concentrate[END_REF], allowing a better intestinal absorption of the nutrients released. Regarding enzyme inhibition, Bonnin and colleagues estimated the concentration of xylanase inhibitors to be around 30 mg/g of wheat [START_REF] Bonnin | Variation in the levels of the different xylanase inhibitors in grain and flour of 20 French wheat cultivars[END_REF] and it was previously concluded that such concentrations are responsible for limiting the efficiency of exogenous xylanase in durum wheat-based diets [START_REF] Ponte | Xylanase Inhibitors Affect the Action of Exogenous Enzymes Used to Supplement Triticum durum-Based Diets for Broiler Chicks[END_REF].

CAZymes inhibitors of plant origin will not be further discussed here, and readers are directed an excellent review on this topic [START_REF] Juge | Plant protein inhibitors of cell wall degrading enzymes[END_REF]. Despite these in vivo constraints, many studies have reported the benefits of CAZymes supplementation in poultry feed.

Xylanases and glucanases, the spearheads of feed enzymes

When talking about the indigestible components in monogastrics feed and enzymes designed for their degradation, it is necessary to consider the cereal base, which constitutes a major part of the diet. Cereals (i.e., wheat, barley, oats and maize) being rich in cellulose, β-glucans and arabinoxylans [START_REF] Choct | Feed Non-Starch Polysaccharides: Chemical Structures and Nutritional Significance[END_REF], the first CAZymes identified for improving digestibility of feedstuffs were glucanases and xylanases. At the time of their implementation on the feed market, around the 1980s, the first benefits observed by farmers were the decrease of foot pad dermatitis occurrence by the improvement of litter quality, and the reduction of feed costs due to an increase of feed efficiency (Bedford and Partridge, 2010). Since then, many in vitro and in vivo experiments have been conducted to better understand their degradation potential on a variety of grain-based diets, and the limits of their action towards recalcitrant NSPs.

The effect of xylanases and glucanases in wheat-or barley-based diets on broilers performance was studied under a number of conditions [START_REF] Cowieson | The effect of conditioning temperature and exogenous xylanase addition on the viscosity of wheat-based diets and the performance of broiler chickens[END_REF][START_REF] Esteve-Garcia | Bioefficacy of enzyme preparations containing beta-glucanase and xylanase activities in broiler diets based on barley or wheat, in combination with flavomycin[END_REF], and the interaction between the two enzymes for improved diet digestibility was evaluated in many in vivo studies [START_REF] Cowieson | Interactions between xylanase and glucanase in maize-soy-based diets for broilers[END_REF]Mathlouthi et al., 2003aMathlouthi et al., , 2003b;;[START_REF] Munyaka | Impact of combined β-glucanase and xylanase enzymes on growth performance, nutrients utilization and gut microbiota in broiler chickens fed corn or wheat-based diets[END_REF]. Noteworthy, some studies have sought to correlate the implementation levels of RSM and SFM in diets with the exogenous supply of a xylanase and glucanase mix [START_REF] Amerah | Effect of different levels of rapeseed meal and sunflower meal and enzyme combination on the performance, digesta viscosity and carcass traits of broiler chickens fed wheat-based diets[END_REF][START_REF] Mushtaq | Influence of sunflower meal based diets supplemented with exogenous enzyme and digestible lysine on performance, digestibility and carcass response of broiler chickens[END_REF]. They

showed that the addition of 1220 IU xylanase and 152 IU glucanase per kilogram of feed in diets containing low amounts of RSM and SFM, allowed the recovery of BWG loss caused by the 50% reduction of PM inclusion. These results are consistent with similar studies conducted on low-energy diets containing SBM [START_REF] Kocher | Effects of Enzyme Combinations on Apparent Metabolizable Energy of Corn-Soybean Meal-Based Diets in Broilers[END_REF][START_REF] Zanella | Effect of enzyme supplementation of broiler diets based on corn and soybeans[END_REF]. However, in diets with high content of RSM and SFM, the addition of exogenous enzymes at these doses was not sufficient to erase the harmful effects of PM high inclusion on BWG and FI [START_REF] Amerah | Effect of different levels of rapeseed meal and sunflower meal and enzyme combination on the performance, digesta viscosity and carcass traits of broiler chickens fed wheat-based diets[END_REF]. These observations suggest that exogenous xylanase and glucanase, used as recommended by the supplier, allow the release of nutrients to supplement a low-energy diet, rather than the breakdown of anti-nutritional compounds in PM-rich diets.

Over the past two decades, the evaluation of xylanase and glucanase addition in the diet also went beyond the measurement of performance parameters, as some studies focused on the gut microbiota response [START_REF] Józefiak | Effect of β-glucanase and xylanase supplementation of barley-and rye-based diets on caecal microbiota of broiler chickens[END_REF]Mathlouthi et al., 2002a;[START_REF] Munyaka | Impact of combined β-glucanase and xylanase enzymes on growth performance, nutrients utilization and gut microbiota in broiler chickens fed corn or wheat-based diets[END_REF], and on the expression of some intestinal enzymes encoding genes [START_REF] Saleh | Exogenous dietary enzyme formulations improve growth performance of broiler chickens fed a low-energy diet targeting the intestinal nutrient transporter genes[END_REF]. Interestingly, based on performance parameters, a ranking of three commercial cocktails containing different hemicellulolytic activities was established. It revealed differences in their efficiency on low-energy corn-SBM-based diets [START_REF] Saleh | Exogenous dietary enzyme formulations improve growth performance of broiler chickens fed a low-energy diet targeting the intestinal nutrient transporter genes[END_REF]. Furthermore, the impacts of xylanase type and dose have been evaluated in recent in vivo trials [START_REF] Bautil | Feed endoxylanase type and dose affect arabinoxylan hydrolysis and fermentation in ageing broilers[END_REF]. Broilers were fed with wheat-soy based diets supplemented by Belfeed™ B1100 and Econase™ XT (two different endo-xylanases preparations mainly developed to target wheat nutrients) at 10, 100 and 1000 mg/kg of feed. Although an improvement of arabinoxylans solubilization was demonstrated for both endo-xylanases, the mode of action and the dose required to observe significant effects appeared to be different, which could be explained by a different substrate specificity between the two enzymes.

On another note, Lafond and colleagues evaluated the effect of xylanase supplementation on the digestion of two wheat cultivars, using an in vitro approach [START_REF] Lafond | In vitro gastrointestinal digestion study of two wheat cultivars and evaluation of xylanase supplementation[END_REF]. In this study, fungal xylanases XynD (GH10) and XynB (GH11) activity on wheat polysaccharides were assessed in the TNO gastrointestinal model-1 mimicking the monogastric metabolism. They demonstrated an increase of xylose, glucose, and arabinose contents in the jejunal dialysates in presence of XynD or XynB, suggesting an improvement of wheat-based diets metabolizable energy, by an alleviation of the "cage effect" caused by arabinoxylans. These data complemented a previous study by the same research group reporting the effect of Rovabio™ Excel on Caphorn and Isengrain wheat cultivars (Lafond et al., 2011). These studies led to the development of a new enzyme preparation, commercialized by Adisseo ® as Rovabio™ Advance. Since then, many in vivo experiments have been conducted with broilers, to confirm the hypotheses made on the basis of in vitro data [START_REF] Cozannet | Dietary Energy and Amino Acid Enhancement From a Multi-enzyme Preparation[END_REF][START_REF] Cozannet | Next-generation non-starch polysaccharide-degrading, multi-carbohydrase complex rich in xylanase and arabinofuranosidase to enhance broiler feed digestibility[END_REF]Yacoubi et al., 2018a). The latest published one deals with the effect of Rovabio™ Advance supplementation in corn-SBM diets on turkey performance [START_REF] Flores | Effect of feed form, soybean meal protein content, and Rovabio Advance on poult live performance to 3 wk of age[END_REF]. Pretreatment of the meal with 200 mL/t of the enzyme cocktail significantly increased the AMEn at 14 days of age and decreased the FCR during starter phase (0-7 days of age). Comprising the traditional duet xylanases and glucanases, the enzymatic cocktail produced by the fermentation of Trichoderma citrinoviride (Advanced Enzyme Technologies) has also proven to be effective at enhancing nutrient utilization in wheat-SBM based diets [START_REF] Ko | Supplementation of enzyme cocktail in chickens diet is an effective approach to increase the utilization of nutrient in wheat-based diets[END_REF]. While monosaccharides concentrations in ileum and ceca were concomitantly increased with enzyme levels added in the diet, FCR was significantly improved, which indicates a better use of nutrients in the gut.

Whereas xylanases and glucanases have mostly been used for their ability to degrade NSPs from the cereal part of feed, studies focusing on the carbohydrates content of PMs showed that cellulose is not their main component. If we take SBM as an example, 8% of NSPs are constituted of cellulose while the remaining part are branched polysaccharides such as pectin, mostly rhamnogalacturonans and arabinogalactans (Bedford and Partridge, 2010;[START_REF] Choct | Feed Non-Starch Polysaccharides: Chemical Structures and Nutritional Significance[END_REF]. To corroborate these assumptions, an in vitro study from 2002 compared the effect of a combination of xylanase and glucanase to an enzymatic cocktail (containing many other enzyme activities), on the viscosity of feedstuffs from different origins (Mathlouthi et al., 2002b). To this end, a total of 15 most frequently used grains and PM were assayed, among them SBM, RSM and SFM. The synergy of xylanase and glucanase significantly reduced viscosity in SBM and RSM after 1h at 39°C

(corresponding to the chicken body temperature), but it had no impact on SFM viscosity. The action of the Quatrazyme HP enzymatic cocktail (Nutri-Tomen) led to a viscosity reduction of 76, 60 and 38% of SBM, RSM and SFM respectively, compared to the control. Although this enzymatic cocktail is no longer available on the feed additives market, it gave significantly better results than the xylanase and glucanase in combination or alone. The measurement of Quatrazyme HP activity on several pNP-osides revealed the presence of arabinofuranosidase (28 IU/mg), galactosidase (2,464 IU/mg), glucosidase (642 IU/mg), polygalacturonase (85,340 IU/mg) and xylosidase (13 IU/mg) activities, explaining its efficiency in decreasing PM viscosity. Hence, this study shows that enriching commercial enzymatic cocktails with debranching and pectin-degrading enzymes is a promising path to improve the digestibility of feedstuffs.

Debranching and pectin-degrading enzymes to upgrade feed digestibility

Debranching enzymes are kind of the Swiss Army knife of enzymes when it comes to the degradation of NSPs, as we can find some similarities in the composition of their ramifications. Indeed, if we look as example the case of L-arabinose, several studies have reported its presence in the side chains of arabinoxylans [START_REF] Saulnier | 2.20 -Plant Cell Wall Polysaccharides in Storage Organs: Xylans (Food Applications)[END_REF] as well as rhamnogalacturonans (I and II) [START_REF] Kaczmarska | Structure and functionality of Rhamnogalacturonan I in the cell wall and in solution: A review[END_REF][START_REF] Lavarack | The acid hydrolysis of sugarcane bagasse hemicellulose to produce xylose, arabinose, glucose and other products[END_REF]. Hence, the diet supplementation with arabinofuranosidases could improve both cereal-base and PM digestibilities. Therefore, the synergy between xylanases and arabinofuranosidases for arabinoxylan degradation have been studied from different angles, and its applications in feed are no longer to be demonstrated [START_REF] Cozannet | Next-generation non-starch polysaccharide-degrading, multi-carbohydrase complex rich in xylanase and arabinofuranosidase to enhance broiler feed digestibility[END_REF][START_REF] Jia | Synergistic degradation of arabinoxylan by free and immobilized xylanases and arabinofuranosidase[END_REF][START_REF] Ravn | Combined endo-β-1,4-xylanase and α-l-arabinofuranosidase increases butyrate concentration during broiler cecal fermentation of maize glucurono-arabinoxylan[END_REF][START_REF] Saleh | Effects of Dietary Xylanase and Arabinofuranosidase Combination on the Growth Performance, Lipid Peroxidation, Blood Constituents, and Immune Response of Broilers Fed Low-Energy Diets[END_REF][START_REF] Ward | Debranching enzymes in corn/soybean meal-based poultry feeds: a review[END_REF]. However, few works have been published on the potential of debranching enzymes for the deconstruction of rhamnogalacturonans in PM-based diets for poultry.

Yet, the harmful effects of pectin on the performance and intestinal health of broilers chickens was already known 40 years ago [START_REF] Ricke | Influence of Dietary Fibers on Performance and Fermentation Characteristics of Gut Contents from Growing Chicks[END_REF]Wagner andThomas, 1978, 1977). More recent studies reported the potential activity of pectic oligosaccharides as prebiotics [START_REF] Babbar | Pectic oligosaccharides from agricultural by-products: production, characterization and health benefits[END_REF]Bonnin et al., 2014;[START_REF] Prandi | Pectin oligosaccharides from sugar beet pulp: molecular characterization and potential prebiotic activity[END_REF], some even evaluating their role as an alternative to antibiotics for simulating broiler chicken production [START_REF] Lysko | No-Antibiotic-Pectin-Based Treatment Differently Modified Cloaca Bacteriobiome of Male and Female Broiler Chickens[END_REF]. Thus, pectin-degrading enzymes, or pectinases, would represent an advantage for poultry nutrition and health both by the compounds they degrade and the products they generate.

As it stands, collecting data on pectinase supplementation in feedstuffs for monogastric animals is quite complex, although several published studies demonstrate the interest of pectinase supplementation in ruminants diets [START_REF] Azzaz | A new pectinase produced from Aspergillus terreus compared with a commercial pectinase enhanced feed digestion, milk production and milk fatty acid profile of Damascus goats fed pectin-rich diet[END_REF][START_REF] Murad | Microbial Pectinases and Ruminant Nutrition[END_REF]. Indeed, pectinases are often studied in combination with cellulases, hemicellulases, phytases and proteases [START_REF] Berwanger | Sunflower cake with or without enzymatic complex for broiler chickens feeding[END_REF][START_REF] Francesch | Enzyme Supplementation of a Barley and Sunflower-Based Diet on Laying Hen Performance[END_REF], but only few studies have investigated their effect alone. Pectinase supplementation at 2 U/kg of feed was tested in a corn-SBM diet fed to broilers but showed no significant effect on performance parameters nor on crude protein digestibility compared to control diet [START_REF] Tahir | Pectinase Plays an Important Role in Stimulating Digestibility of a Corn-Soybean Meal Diet in Broilers[END_REF]. In contrast, a synergy of the same pectinase with hemicellulases and cellulases, applied at 2 and 0.33 U/kg of feed respectively, was observed through an increase of crude protein digestibility and AME in the ileum of birds. These results should be treated with caution as the enzyme doses applied to the diet are not expressed using IU and that no information is given on the enzyme activity measurement. To go further on enzyme mix displaying pectinase activity, Kocher and colleagues studied the effect of two CAZymes cocktails on corn-SBM diets fed to broilers, one containing pectinase activity (Ronozyme™ VP) and another one galactanase activity (supplied by Novozymes ® ). Both mixtures showed no effect on performance parameters compared to control group, although high doses of Ronozyme™ VP improved ileal protein digestibility [START_REF] Kocher | Effects of feed enzymes on nutritive value of soyabean meal fed to broilers[END_REF].

Along the same line of thoughts, the effect of an enzyme mixture containing cellulases, hemicellulases and pectinases, was compared to an enzyme cocktail commercialized as Energex™, on broilers performance [START_REF] Saleh | A mixture of pure cellulase, hemicellulase and pectinase improves broiler performance[END_REF]. Both mixtures improved the BWG and FCR compared to control group, even though no impact on apparent intestinal viscosity was observed in presence of the pectinase-containing mixture. This result may seem surprising when we know that pectin is largely responsible for the viscosity of the feed bowl, but it could be explained by the diversity of pectins and pectinases.

Unlike cellulose-or hemicellulose-degrading enzymes, the activity of the pectinolytic enzymes used in these studies is rarely, if ever, specified. Most of the published works on pectin-degrading enzymes use the generic name "pectinase", while many different enzymes would be necessary to completely degrade pectin [START_REF] Bonnin | Pectin Degrading Enzymes[END_REF][START_REF] Garg | Microbial pectinases: an ecofriendly tool of nature for industries[END_REF][START_REF] Sharma | Microbial pectinase: sources, characterization and applications[END_REF][START_REF] Zheng | Pectinolytic lyases: a comprehensive review of sources, category, property, structure, and catalytic mechanism of pectate lyases and pectin lyases[END_REF]. Even more, as the deconstruction of RG-II would require no less than 21 distinct activities due to the great complexity of glycosidic linkages composing it [START_REF] Ndeh | Complex pectin metabolism by gut bacteria reveals novel catalytic functions[END_REF]. Noteworthy, the synergy of polygalacturonase with a putative RG-I debranching enzyme for SBM degradation in broilers diets was studied in vitro [START_REF] Vahjen | Study on the use of soya bean polysaccharide degrading enzymes in broiler nutrition[END_REF]. Used alone, 1,4-β-arabinogalactanase showed a high rate of reducing sugars release from SBM, and this rate was increased in presence of endo-polygalacturonase. However, this synergy could not be confirmed in vivo, as BWG and FI of broilers were significantly reduced when the diet was supplemented by these enzymes, compared to the control-diet. The authors hypothesized that, due to the high enzyme doses tested (37,320 and 116,200 IU/kg of feed, respectively), an intense and anti-nutritive hydrolysis of NSPs from SBM occurred in the digestive tract, releasing oligomers disturbing the intestinal osmotic balance. These results raise the question of beneficial-to-deleterious enzyme dose, which was also previously underlined by a study on pectinases for lupin pectin hydrolysis in broiler nutrition [START_REF] Ali | Hydrolysis of lupin pectin by pectinases for broiler[END_REF].

Apart from PM, some research groups took interest in pectinase supplementation to increase the nutritive value of peas as protein source for broilers. In 1997, a study showed that the addition of pectinase at 50 IU/kg of feed did not improve the growth rate, nor the FI and FCR of broilers compared to the control group [START_REF] Igbasan | The effect of pectinase and α-galactosidase supplementation on the nutritive value of peas for broiler chickens[END_REF]. These results can be discussed regarding the quantity of pectinases supplied in the diet. Other research teams chose to add up to 2,000 IU of pectinase per kilogram of corn-SBM feed [START_REF] Selim | Effect of pectinase enzyme supplementation and low-energy corn-soybean diets on broilers performance and quality of carcass and meat[END_REF][START_REF] Tahir | Pectinase Plays an Important Role in Stimulating Digestibility of a Corn-Soybean Meal Diet in Broilers[END_REF], and eventually demonstrated that ileal digestibility, breast muscle and AMEn are enhanced by the combination of cellulases, hemicellulases and pectinases, compared to a diet supplied only by pectinases. In a similar vein, a more recent study compared the supplementation of NSP-degrading enzymes in SBM-and peas-based diets for turkeys. To this end, they used a commercial product containing pectinases, xylanases, glucanases, mannanases, cellulases and galactanases from Canadian Bio-Systems Inc. Based on ileal digesta viscosity, enzyme activity of cecal bacteria, and SCFA quantification, they concluded that NSP-degrading enzymes have a positive impact on gut physiology and growth performance [START_REF] Zduńczyk | The effect of NSP-degrading enzymes on gut physiology and growth performance of turkeys fed soybean meal and peas-based diets[END_REF]. On another note, Dittoe and colleagues recently assessed the probiotic potential of a bacterial strain through its wide pectinase-producing capacity [START_REF] Dittoe | Assessment of a Potential Role of Dickeya dadantii DSM 18020 as a Pectinase Producer for Utilization in Poultry Diets Based on in silico Analyses[END_REF]. Using an in-silico strategy, they concluded that the strain Dickeya dadantii DSM 18020 has the genetic potential to produce multiple pectin-degrading enzymes that could be beneficial in poultry nutrition. This new kind of approach coincides with the growing interest in the relationship between feed composition and microbiota population, which is in line with the statement that performance gains and gut health are tightly interconnected [START_REF] Choct | Managing gut health through nutrition[END_REF].

HEALTH BENEFITS PROVIDED BY EXOGENOUS CAZYMES IN FEED

CAZymes as a solution to tackle the challenges of antibiotics-free farming

In recent years, meat consumers' expectations have increasingly focused on environmental friendliness and livestock welfare. One of the main concerns is directed to the systematic use of antibiotics as growth promoters in animal feed. Although prohibited in EU since 2006 and more recently in a growing number of other countries like Canada, this practice is still used in many countries, despite its recognized role in promoting antibiotic resistance [START_REF] Agyare | Antibiotic Use in Poultry Production and Its Effects on Bacterial Resistance, Antimicrobial Resistance -A Global Threat[END_REF][START_REF] Mehdi | Use of antibiotics in broiler production: Global impacts and alternatives[END_REF]. In addition to contributing to the development of multi-drugs resistant bacteria, using antibiotics as growth promoters in feedstuffs can be a threat for the consumer's health and the environment [START_REF] Bennani | Overview of Evidence of Antimicrobial Use and Antimicrobial Resistance in the Food Chain[END_REF][START_REF] Iwu | The incidence of antibiotic resistance within and beyond the agricultural ecosystem: A concern for public health[END_REF][START_REF] Verraes | Antimicrobial Resistance in the Food Chain: A Review[END_REF]. Therefore, addressing these concerns is equally a challenge and an opportunity for the farming industry. Indeed, animal health and performance gains are closely related [START_REF] Choct | Managing gut health through nutrition[END_REF]. Many innovative alternatives to antibiotics have been developed, one of them being the use of exogenous enzymes as feed additives. Their mode of action promotes the reduction of feed viscosity by hydrolyzing the polysaccharides initially fermented by microbial pathogens, and enhances access to nutrients for beneficial flora, through the production of prebiotic oligosaccharides [START_REF] El-Hack | Hot red pepper powder as a safe alternative to antibiotics in organic poultry feed: an updated review[END_REF][START_REF] Mahlake | Green Tea (Camellia sinensis) Products as Alternatives to Antibiotics in Poultry Nutrition: A Review[END_REF][START_REF] Mehdi | Use of antibiotics in broiler production: Global impacts and alternatives[END_REF].

The modulation of gut microbiota and intestine inflammation through enzyme supplementation

As explained above, PM contain NSPs (soluble and insoluble) and oligosaccharides, acting as antinutritional factors by limiting nutrient assimilation. Beyond their antinutritional power, it has been shown that NSPs can negatively impact several gut health parameters such as the intestinal microbial homeostasis, depending on their type and content in the diet. In 2018, an in vivo trial aimed to assess the effect of sNSP and iNSP on multiple health parameters was conducted, by adding 3% pectin, carboxymethyl cellulose or cellulose into the diet [START_REF] Kermanshahi | Effects of non-starch polysaccharides in semi-purified diets on performance, serum metabolites, gastrointestinal morphology, and microbial population of male broiler chickens[END_REF]. This study shows that at these inclusion levels, depending on the type of NSP, the effects are different. A reduction of beneficial bacteria counts into the ileum (i.e., Lactobacillus spp. and Bifidobacterium spp.) and a decrease of BWG were observed when broilers were fed with sNSP (pectin and CMC) supplemented diets.

However, no significant effect was observed on the microbial community with a cellulose-enriched diet compared to the control diet. Earlier, the effect of several diets supplemented or not by complex carbohydrates was investigated, by evaluating necrotic enteritis lesions in broilers induced with the major poultry intestinal pathogen, Clostridium perfringens [START_REF] Branton | The effect of added complex carbohydrates or added dietary fiber on necrotic enteritis lesions in broiler chickens[END_REF]. Diets supplemented with pectin, gum guar or pine shavings, exhibited the higher scores of intestinal lesions and mucosal inflammation, suggesting a promotion of the gut colonization by the pathogen. A more recent study aimed at comparing the cecal microbiota composition of broilers between SBM-and fermented SBMcontaining diets [START_REF] Li | Effects of Fermented Soybean Meal Supplementation on the Growth Performance and Cecal Microbiota Community of Broiler Chickens[END_REF]. An increase of beneficial flora and a decrease of pathogenic phyla was observed when SBM was replaced by fermented SBM in the diet, suggesting the pre-treatment of SBM helped degrading the polysaccharides into products having a prebiotic effect on broilers microbiota. In addition to the polysaccharides effects on microbial population, some oligosaccharides produced by NSPs enzymatic degradation have been found to prevent adhesion of enteropathogenic Escherichia coli to human colon cells, and to reduce the population of Salmonella in broilers' caeca [START_REF] Shoaf | Prebiotic Galactooligosaccharides Reduce Adherence of Enteropathogenic Escherichia coli to Tissue Culture Cells[END_REF][START_REF] Spring | The effects of dietary mannaoligosaccharides on cecal parameters and the concentrations of enteric bacteria in the ceca of salmonella-challenged broiler chicks1[END_REF]. In the same idea, the effect of arabinoxylans pretreated or not by Rovabio™ Excel on microbiota composition, SCFA concentration and immune cells infiltration in the intestine of broilers was investigated (Yacoubi et al., 2018b). An increase of butyrate-producing bacteria population in the caeca was observed, which may reflect a reduction of the inflammation in the lower intestine, as butyrate could be involved in gut inflammatory response [START_REF] Canani | Potential beneficial effects of butyrate in intestinal and extraintestinal diseases[END_REF][START_REF] Chen | The Role of Butyrate in Attenuating Pathobiont-Induced Hyperinflammation[END_REF]. These results were consistent with the decrease of immune cells in the intestinal mucosa, and similar studies also led to the conclusion that NSP-degrading enzymes contribute to the intestinal homeostasis of broilers [START_REF] Mikulski | The effect of dietary faba bean and non-starch polysaccharide degrading enzymes on the growth performance and gut physiology of young turkeys[END_REF][START_REF] Zduńczyk | The effect of NSP-degrading enzymes on gut physiology and growth performance of turkeys fed soybean meal and peas-based diets[END_REF]. To further explore this topic, the relationship between dietary fiber, nutrient utilization, and intestinal health in poultry was skillfully reviewed in 2021 [START_REF] Singh | Effects of Dietary Fiber on Nutrients Utilization and Gut Health of Poultry: A Review of Challenges and Opportunities[END_REF].

The impact of exogenous CAZymes on animal physiology

In addition to microbiome parameters, a few research groups took interest in the direct effect of exogenous enzymes on broilers' health. Based on hematological and biochemical serum parameters, no impact of xylanase oral intake was observed on blood cells count nor on kidney and liver markers [START_REF] Ahmad | Effect of Oral Application of Xylanase on Some Hematological and Serum Biochemical Parameters in Broilers[END_REF]. Although the research approach is noble, as there is a paucity of data about the direct effect of feed enzymes on animal health, no information is given on the provenance and the formulation of the xylanase used. Likewise, the experiment was conducted on a small population -15 birds per conditionleading to questioning the conclusions made in this study. The quantification of intestinal enzymes encoding genes in broilers is also an approach that have been reported several times.

Among frequently targeted genes are GLUT2, coding a monosaccharide (i.e., glucose, galactose, fructose) intestinal transporter, and PEPT1, coding a protein involved in the uptake of di-and tripeptides from the lumen by enterocytes. In a 2018 study, GLUT2 and PEPT1 were shown to be up-regulated when chickens were fed with xylanase-supplemented diets, suggesting a promotion of nutrients absorption thanks to the action of the exogenous enzyme [START_REF] Saleh | Exogenous dietary enzyme formulations improve growth performance of broiler chickens fed a low-energy diet targeting the intestinal nutrient transporter genes[END_REF]. These observations are consistent with previously published works [START_REF] Guo | Xylanase supplementation of a wheat-based diet improved nutrient digestion and mRNA expression of intestinal nutrient transporters in broiler chickens infected with Clostridium perfringens[END_REF][START_REF] Hosseini | Effects of Xylanase Supplementation and Citric Acid on Performance, Ileal Nutrients Digestibility, and Gene Expression of Intestinal Nutrient Transporters in Broilers Challenged with Clostridium perfringens[END_REF].

On another note, the supplementation of corn-SBM diets with several NSP-degrading enzymes led to the improvement of intestinal morphology parameters such as the villus length and the crypt depth [START_REF] Zou | Effects of exogenous enzymes and dietary energy on performance and digestive physiology of broilers[END_REF].

Overall, the impact of enzymatic cocktails on animal health as such remains scarcely documented. Most published studies focus on performance gains through the improvement of some health indicators, but only few of them are really dedicated to this topic. This lack of data can be partly explained by the difficulty of setting up in vivo experiments, although alternative in vitro models are democratizing in the field [START_REF] Sharma | Artificial gut and the applications in poultry: A review[END_REF]. Nevertheless, recent reviews managed to depict quite broadly the role of exogenous feed enzymes in promoting gut health of monogastrics, and to which extend their action modulates animal physiology [START_REF] Anadón | Enzymes in Feed and Animal Health[END_REF][START_REF] Kiarie | The role of added feed enzymes in promoting gut health in swine and poultry[END_REF].

Remarkably, by discussing the effects of fibers and NSPs on chicken gut microbiota, a 2019 review highlighted that the composition of the diet can have a direct impact on brain and liver through the production of SCFAs [START_REF] Mahmood | Dietary fiber and chicken microbiome interaction: Where will it lead to?[END_REF]. The production of SCFAs is conditioned by an organized chain of events, including the breakdown of fibers into absorbable units by microbial and/or intestinal enzymes, and the nutrients assimilation by enterocytes' enzymatic arsenal. As presented earlier, exogenous enzymes, namely CAZymes, have a positive impact on both of these parameters, since the degradation of NSPs in the gut promote the expression of intestinal enzyme encoding genes [START_REF] Saleh | Exogenous dietary enzyme formulations improve growth performance of broiler chickens fed a low-energy diet targeting the intestinal nutrient transporter genes[END_REF]. This suggests they play a prebiotic key role that could indirectly modulate animal physiology through the "gut-brain" and "gut-liver" axis [START_REF] Mahmood | Dietary fiber and chicken microbiome interaction: Where will it lead to?[END_REF]. This prebiotic activity is not provided by the enzymes as such, but rater by the residues they produce. For example, pectin has a detrimental effect on nutrient absorption by increasing feed bowl viscosity, but its enzymatic degradation products are recognized as prebiotics. Among them we can mention oligogalacturonides, galactooligosaccharides and rhamnogalacturonan-oligosaccharides [START_REF] Babbar | Pectic oligosaccharides from agricultural by-products: production, characterization and health benefits[END_REF], as well as phenolic and antioxidant compounds [START_REF] Bao | Dietary NSP nutrition and intestinal immune system for broiler chickens[END_REF][START_REF] Liu | Complex enzyme hydrolysis releases antioxidative phenolics from rice bran[END_REF].

Better understanding the effect of these prebiotics, through the study of their composition, structure, and the way they interact with the host [START_REF] Montagne | A review of interactions between dietary fibre and the intestinal mucosa, and their consequences on digestive health in young non-ruminant animals[END_REF][START_REF] Wang | Effects of Dietary Zinc Pectin Oligosaccharides Chelate Supplementation on Growth Performance, Nutrient Digestibility and Tissue Zinc Concentrations of Broilers[END_REF], is a leverage of feed enzymatic cocktails development. Indeed, the enzymes of interest for health and performance gains could either be determined by looking at the substrates we want to degrade, or by selecting the final products we want them to generate. Using these two approaches would be a way to guarantee the robustness and efficiency of enzymatic cocktails on multiple feedstuffs.

GENERAL CONCLUSIONS AND OUTLOOKS

In a world where carbon footprint, bioeconomy and sustainability are of utmost importance for most countries and industrial companies, it is urgent to find solutions to reduce food losses and avoid the competition between food and feed. The valorization of oilseed meals as protein source in feedstuffs has proven to be an efficient way to answer these questions. It has been shown that the competition for croplands between food and feed has decreased over the past two decades, from a total feed cropland area of 50% in 1980s to 37% nowadays [START_REF] Maisonnier-Grenier | Feeding proteins to livestock: Global land use and food vs. feed competition[END_REF]. Agricultural co-products valorization in feed has been greatly facilitated and promoted by the appearance of enzymatic cocktails and feed additives. The global feed enzymes market it is expected to reach 3.8 billion USD during the forecast period 2022[START_REF]Feed Enzymes Market Research Report: Information By Type (Protease, Phytase and others), Livestock (Swine, Poultry, Ruminants, Aquatic Animals and others), Form (Dry, Liquid and others), By Region[END_REF](Market Research Future, 2022), which can be explained by the economic, ecological, and societal advantages of enzymatic cocktails designed for feed. Their economic and societal benefits have been presented along this review, notably through their efficiency in improving animal performance [START_REF] Zou | Effects of exogenous enzymes and dietary energy on performance and digestive physiology of broilers[END_REF] and their usefulness in moving towards an antibiotic-free farming system. Among the environmental benefits provided by exogenous enzymes in feed, we can note the reduction of pollutant emissions by livestock thanks to an enhanced nutrients assimilation [START_REF] Li | TECHNOLOGY PROSPECTING ON ENZYMES: APPLICATION[END_REF]. Addition of exogenous enzymes also helped reducing the ammonia emissions in wheat-SBM diets fed to monogastrics [START_REF] Garry | Effect of cereal type and exogenous enzyme supplementation in pig diets on odour and ammonia emissions[END_REF].

Today, many enzymes solutions (singles, blends, or cocktails) are available on the market for the degradation of fibers in the diet of monogastric animals. For several years, they have been developed, optimized, supplemented, and upgraded, leading to a large catalog of enzymatic systems.

In vitro studies on the structure and the composition of diet components helped the continuous improvement of enzymes mixtures [START_REF] Bao | Functional patterns of exogenous enzymes in different feed ingredients[END_REF]. However, animal gut being a hostile environment for exogenous enzymes [START_REF] Ravindran | Feed enzymes: The science, practice, and metabolic realities[END_REF], it can be difficult to highlight the beneficial effect of enzymes in vivo when looking only at performance parameters. The decrease of enzyme efficiency during feed pre-treatment processes, the extreme conditions in the digestive tract, and the variability of in vivo trials are often encountered in animal feed (Bedford and Partridge, 2010;[START_REF] Ravindran | Feed Enzyme Technology: Present Status and Future Developments[END_REF]. Therefore, important parameters like knowledge of fibers structures and NSPs contents in raw materials, pH, thermostability and kinetics of individual enzymes are to be considered when developing a complex enzymatic cocktail. Taking these constraints into consideration led to the optimization of enzyme formulations to increase the robustness of commercial cocktails for NSPs degradation in feed [START_REF] Cowieson | Evolving enzyme technology: impact on commercial poultry nutrition[END_REF][START_REF] Ravindran | Feed enzymes: The science, practice, and metabolic realities[END_REF][START_REF] Velázquez-De Lucio | Exogenous Enzymes as Zootechnical Additives in Animal Feed: A Review[END_REF].

Computational biology and its recent advances, as well as the continuous mining for new enzymes in microbial metagenomes are other ways to guarantee the constant evolution of enzymes for the feed industry, driving protein engineering towards increased stability and efficiency of cocktails [START_REF] Suplatov | Robust enzyme design: Bioinformatic tools for improved protein stability[END_REF]. Beyond robustness, enzyme specificity and affinity for feed NSPs also needs to be considered. Diving into the structural characterization of oilseed meals carbohydrates to better target the enzymatic activities required is therefore an avenue of evolution for the feed industry.

It is however worthy to note that the excessive use of PM to formulate diets for monogastric animals have recently been discussed regarding their impact on the environment. The use of SBM in feed has been criticized in particular because of its intense importation all around the world and the CO2 emissions it represents (de Vries and de Boer, 2010; [START_REF] Vellinga | Environmental impact of livestock feed[END_REF]. For this reason, many countries are today looking for local alternatives to SBM as protein source for animal feed [START_REF] Choi | Effects of dietary hatchery by-products on growth performance, relative organ weight, plasma measurements, immune organ index, meat quality, and tibia characteristics of broiler chickens[END_REF][START_REF] Gu | Fermented Cottonseed Meal as a Partial Replacement for Soybean Meal Could Improve the Growth Performance, Immunity and Antioxidant Properties, and Nutrient Digestibility by Altering the Gut Microbiota Profile of Weaned Piglets[END_REF][START_REF] Khan | Worm meal: a potential source of alternative protein in poultry feed[END_REF][START_REF] Khan | Recent advances in role of insects as alternative protein source in poultry nutrition[END_REF][START_REF] Parolini | Earthworm as an alternative protein source in poultry and fish farming: Current applications and future perspectives[END_REF]. The efficiency of feed enzymes on these new protein sources are also being investigated [START_REF] Aftab | Utilization of alternative protein meals with or without multiple-enzyme supplementation in broilers fed low-energy diets[END_REF][START_REF] Saleh | Effect of dietary incorporation of peanut and linseed meals with or without enzyme mixture on physiological performance of broilers[END_REF].

Nevertheless, finding alternatives to SBM in animal feed is challenging, if we consider the amounts of alternative products that would be needed, to match the current productions and competitive prices of SBM. Therefore, enzymes producers must constantly seek to improve and adjust their cocktails, to meet the various economic and ecological challenges the animal feed industry is facing. Inspired by the optimization of enzymatic cocktails for the biofuel industry that allowed the degradation of highly recalcitrant substrates, the versatility of enzymatic cocktails designed for feed, and their adaptation to a variety of future scenarios, is one way to shape the sustainability of the feed industry.

Funding

PhD fellowship of L.P. was funded by Adisseo and the "Association Nationale Recherche

Technologie" (ANRT) through the Convention Industrielle de Formation par la RecherchE (CIFRE) grant no. 2021/1432.

Figure 1 .

 1 Figure 1. Non-starch polysaccharides content of oilseeds. (Modified from[START_REF] Agger | Enzymatic Xylose Release from Pretreated Corn Bran Arabinoxylan: Differential Effects of Deacetylation and Deferuloylation on Insoluble and Soluble Substrate Fractions[END_REF][START_REF] Attia | Recent structural insights into the enzymology of the ubiquitous plant cell wall glycan xyloglucan[END_REF]

  . While going through the process of oil extraction, the structure of oilseeds cell walls is modified, and the carbohydrates content of the meals is concentrated in non-starch polysaccharides. Due to a lack of oilseeds meals characterization, the non-starch polysaccharide structures presented herein are standard structures, reported for different plant sources than oilseeds. These structures can vary in oilseeds meals, depending on multiple parameters such as the extraction method and the origin of the seeds. HG: homogalacturonan ; XG: xylogalacturonan ; RG-I: rhamnogalacturonan-I ; RG-II: rhamnogalacturonan-II ; D-Dha: 2-keto-3-deoxy-D-lyxo-heptulosaric acid ; D-Kdo: ketodeoxymanno-octulopyranosylonic acid

Figure 2 .

 2 Figure 2. CAZymes for NSPs degradation. Listed from Labourel et al., 2019; Hage and Rosso, 2021. LPMO: lytic polysaccharide monooxygenase.

Table 2 . History of the in vitro characterization of Rovabio™ range enzymatic cocktails.

 2

	YEAR	FOCUS OF THE STUDY	REFERENCES
		Effect of three wheat proteins inhibitors on the GH11 endo-1,4-β-D-xylanase (XynC) from P. funiculosum	Furniss et al., 2002
		Effect of wheat proteinaceous inhibitors on GH11 endo-1,4-β-D-xylanase (XynB) from P. funiculosum	Brutus et al., 2004
		Effect of three wheat proteins inhibitors on the
		endo-1,4-β-D-xylanases XynA, XynB and XynD from	Furniss et al., 2005
		P. funiculosum
		In vitro efficiency and mode of action of Rovabio™ Excel in wheat-based diets	Maisonnier-Grenier et al., 2006
		Characterization of GH11 endo-1,4-β-D-xylanase (XynC) from P. funiculosum	Berrin et al., 2007
		Proteomics analysis of P. funiculosum secreted enzymes	Guais et al., 2008
		Characterization of endo-1,4-β-D-glucanase, β-glucosidase and cellobiohydrolase from P. funiculosum	Karboune et al., 2008
		Characterization of the family GH54 arabinofuranosidases of P. funiculosum	Guais et al., 2010
		Characterization of GH10 endo-1,4-β-D-xylanase (XynD) from P. funiculosum	Lafond et al., 2011
		Efficiency of Rovabio™ Excel supplementation in wheat-based diets using an in vitro gastrointestinal model	Lafond et al., 2011
		Reclassification of XynA from P. funiculosum IMI 378536 as a GH7 cellobiohydrolase	Texier et al., 2012
		Characterization of three GH62 α-L-arabinofuranosidases from P. funiculosum	De La Mare et al., 2013
		Comparison of GH11 xylanases XynC from P. funiculosum and Pol6 from P. occitanis	Driss et al., 2013
		Characterization of the activity of four GH11 xylanases from T. versatilis on arabinoxylans	Lafond et al., 2014
		In vitro efficiency of GH10 xylanase XynD and GH11 xylanase
		XynB from P. funiculosum on the digestion of two wheat	Lafond et al., 2015
		cultivars
		Genomic characterization of T. versatilis	Guais et al., 2017
		In vitro comparison of Rovabio™ Excel and Rovabio™ Advance for improving the digestibility of cereal fractions	Vangsøe et al., 2021

National Research Council (United States