Tarryn E Miller

Thomas Beneyton

Thomas Schwander

Christoph Diehl

Mathias Girault

Richard Mclean

Tanguy Chotel

Peter Claus

Socorro Niña

Jean-Christophe Cortina

Baret

Niña Socorro Cortina

Jean- Christophe Baret
email: jean-christophe.baret@u-bordeaux.fr

Tobias J Erb
email: toerb@mpi-marburg.mpg.de

Light-powered CO 2 fixation in a chloroplast mimic with natural and synthetic parts

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Main

The photosynthetic transformation of inorganic carbon into organic matter is a fundamental biological process, responsible for the vast majority of stored energy and biomass on Earth. This process is spatially and temporally controlled and highly integrated with other cellular functions.

Photosynthesis ultimately converts light energy through membrane bound protein complexes into the energy-rich chemical cofactors adenosine triphosphate (ATP) and reduced nicotinamide adenine dinucleotide phosphate (NADPH). ATP and NADPH are subsequently used to fuel metabolic processes, in particular the fixation of carbon dioxide (CO2) through the Calvin-Benson-Bassham (CBB) cycle [START_REF] Bassham | The path of carbon in photosynthesis[END_REF].

The principle of photosynthesis has been the inspiration for artificial systems that use the energy of light for the controlled capture and conversion of CO2 into useful compounds [START_REF] Liu | Water splitting-biosynthetic system with CO2 reduction efficiencies exceeding photosynthesis[END_REF][START_REF] Jensen | Light-driven chemical synthesis[END_REF][START_REF] Schwille | MaxSynBio: Avenues Towards Creating Cells from the Bottom Up[END_REF][START_REF] Sokol | Bias-free photoelectrochemical water splitting with photosystem II on a dye-sensitized photoanode wired to hydrogenase[END_REF][START_REF] Guo | Light-driven fine chemical production in yeast biohybrids[END_REF][START_REF] Sakimoto | Self-photosensitization of nonphotosynthetic bacteria for solar-to-chemical production[END_REF][START_REF] Zhang | Selective aerobic oxidation reactions using a combination of photocatalytic water oxidation and enzymatic oxyfunctionalizations[END_REF][START_REF] Litman | Cooperative asymmetric reactions combining photocatalysis and enzymatic catalysis[END_REF]. Two recent developments in bio-and nanotechnology promise to afford integrated systems of higher efficiency, approaching or rivaling that of natural biological systems. One is the emergence of microfluidics as technology platform to manipulate and assemble constitutive elements and functions of living systems in miniaturized and confined environments [START_REF] Schwille | MaxSynBio: Avenues Towards Creating Cells from the Bottom Up[END_REF][START_REF] Beneyton | Out-of-equilibrium microcompartments for the bottom-up integration of metabolic functions[END_REF][START_REF] Weiss | Sequential bottom-up assembly of mechanically stabilized synthetic cells by microfluidics[END_REF][START_REF] Deshpande | Spatiotemporal control of coacervate formation within liposomes[END_REF][START_REF] Hasatani | High-throughput and long-term observation of compartmentalized biochemical oscillators[END_REF][START_REF] Dupin | Signalling and differentiation in emulsion-based multicompartmentalized in vitro gene circuits[END_REF][START_REF] Booth | Light-patterning of synthetic tissues with single droplet resolution[END_REF][START_REF] Booth | Spatial Positioning and Chemical Coupling in Coacervate-in-Proteinosome Protocells[END_REF]. The second is the successful design and realization of complex biomimetic modules and systems from defined biological parts. Recent examples are metabolically active micro-compartments, artificial lightharvesting organelles [START_REF] Berhanu | Artificial photosynthetic cell producing energy for protein synthesis[END_REF][START_REF] Lee | Photosynthetic artificial organelles sustain and control ATP-dependent reactions in a protocellular system[END_REF][START_REF] Feng | Coassembly of Photosystem II and ATPase as Artificial Chloroplast for Light-Driven ATP Synthesis[END_REF][START_REF] Buddingh | Artificial Cells: Synthetic Compartments with Lifelike Functionality and Adaptivity[END_REF], advanced transcription-translation (TX-TL) circuits [START_REF] Tayar | Synchrony and pattern formation of coupled genetic oscillators on a chip of artificial cells[END_REF][START_REF] Yelleswarapu | Sigma Factor-Mediated Tuning of Bacterial Cell-Free Synthetic Genetic Oscillators[END_REF] or complex in vitro metabolic networks [START_REF] Schwander | A synthetic pathway for the fixation of carbon dioxide in vitro[END_REF][START_REF] Srinivas | Enzyme-free nucleic acid dynamical systems[END_REF][START_REF] Dudley | Cell-free metabolic engineering: Biomanufacturing beyond the cell[END_REF]. Yet, the combination of these individual modules into more complex systems remains a challenge [START_REF] Booth | Functional aqueous droplet networks[END_REF]. Here we developed a platform for the automated assembly of picoliter-sized reaction compartments that enable the light-driven conversion of CO2 into multi-carbon compounds (i.e. glycolate), mimicking the function of chloroplasts.

In photosynthesis, thylakoid membranes provide the energy for CO2-fixation, and we desired to exploit this ability directly for biocatalytic and synthetic biological applications. To establish a module for the light-driven regeneration of ATP and NADPH, we isolated thylakoid membranes from the chloroplasts of Spinacia olecaera. At 100 µmol photons m -2 s -1 these thylakoid preparations catalyzed the light-dependent reduction of NADP + to NADPH (with concomitant oxygen evolution) at a specific activity of 3.41 ± 0.01 µmol min -1 µg -1 total chlorophyll (chlorophyll A and B, referred to as Chl; Fig. 1A), which is comparable to values measured by others (Table S1). NADPH regeneration required the addition of external ferredoxin, with an optimum concentration of 5 µM. Supply of external ferredoxin:NADP + reductase (FNR) did not increase activity further (Fig. S1A andS6A). Addition of superoxide dismutase and catalase to scavenge reactive oxygen species (ROS) resulted in prolonged thylakoid membrane activity (Fig. S2D). In the following, we used light intensities between 50-60 µmol photons m -2 s -1 to further minimize the formation of ROS damaging the photosynthetic apparatus (e.g. the D1-subunit), while providing sufficient rates of NADPH regeneration (Fig. S2E).

Thylakoid membranes also catalyzed the regeneration of ATP from ADP, both in the light and the dark. ATP regeneration in the dark was quantified at 1.2 ± 0.2 µM min -1 µg -1 Chl, attributed to membrane bound adenylate kinases [START_REF] Murakami | Adenylate kinase bound to the envelope membranes of spinach chloroplasts[END_REF], which could be suppressed by using an adenylate kinase specific inhibitor, diadenosine pentaphosphate (DAPP) [START_REF] Strand | The higher plant plastid NAD(P)H dehydrogenase-like complex (NDH) is a high efficiency proton pump that increases ATP production by cyclic electron flow[END_REF][START_REF] Lienhard | Secemski, P1,P5-Di(adenosine-5')pentaphosphate, a Potent Multisubstrate Inhibitor of Adenylate Kinase[END_REF] (Fig. S1C). In the light, ATP production from ADP increased 6-fold (6.5 ± 0.5 µM min -1 µg -1 Chl) and with the addition of DAPP, resulting in a light-(and ATPase-) dependent ATP synthesis rate of 5.4 ± 0.5 µM min -1 µg - 1 Chl (Fig. 1B), comparable to previous studies (Table S1). The specific activities of thylakoid membranes varied slightly between individual preparations (Fig. S1E). Thylakoid membranes were stably maintained in the dark for at least two hours at room temperature and at least 24 hours when maintained on ice with no observable loss of NADPH productivity upon illumination (Fig. S1D). Membrane preparations could be stored at -80 °C for more than a year without notable loss of activity (Fig. S1E), demonstrating their usability as thylakoid membrane-based energy modules (TEM).

Next, we tested the ability of the TEM to energize individual enzyme reactions. We coupled the TEM with two different CO2-fixing enzymes, namely crotonyl-CoA carboxylase/reductase (Ccr) and propionyl-CoA carboxylase (Pcc), which require NADPH and ATP, respectively (Fig. 1C).

In case of Ccr, product formation was strictly light-dependent with a CO2-fixation rate of 5.2 ± 0.2 µM min -1 µg -1 Chl (Fig. 1D). Pcc showed a light-dependent CO2-fixation rate of 5.1 ± 0.2 µM min - 1 µg -1 Chl (Fig. 1D), and a low, light-independent carboxylation rate of 0.8± 0.1 µM min -1 µg -1 Chl, due to the adenylate kinase activity of the TEM (see above). Notably, these carboxylation rates are more than three orders of magnitude higher than recent efforts to couple enzymatic CO2-fixation to isolated PSII (approx. 6.9•10 4 molecules h -1 per PSII reaction center compared to 34 molecules h -1 per PSII reaction center, Table S2), highlighting the capability of our TEM to energize catalytic transformations.

We sought to test the capacity of the TEM to not only power individual CO2-fixing reactions, but a complete metabolic cycle for the continuous fixation of CO2. To that end we combined the 16 enzymes of the CETCH cycle (version 5.4) [START_REF] Schwander | A synthetic pathway for the fixation of carbon dioxide in vitro[END_REF], an artificial pathway for the fixation of CO2 in vitro, and a glyoxylate/hydroxypyruvate reductase from Escherichia coli (Ghr) with the TEM (Fig. 2A). Initial efforts to operate the CETCH cycle together with the TEM failed, indicating a negative interaction of system components (Fig. S3). One problem was an intrinsic hydratase activity of TEMs converting crotonyl-CoA into 3-hydroxybutyryl-CoA (Fig. S5), which we addressed by the addition of a crotonase from P. aeruginosa (PhaJ) [START_REF] Fukui | Expression and Characterization of (R)-Specific Enoyl Coenzyme A Hydratase Involved in Polyhydroxyalkanoate Biosynthesis by Aeromonas caviae[END_REF] for metabolite proof-reading [START_REF] Sun | Metabolite damage and repair in metabolic engineering design[END_REF]. Further analysis suggested that the flavin adenine dinucleotide (FAD)-dependent enzymes methylsuccinyl-CoA oxidase (Mco) and propionyl-CoA oxidase (Pco) interfered with TEM productivity, likely due to the formation of ROS and free FAD in the enzyme preparation (Fig. S6). The latter is capable of directly oxidizing NADPH through the interaction with FNR (see also Fig. S3A, S3B, S6B, S6C). When we replaced Pco with Pcc and added Ghr as an output module (creating CETCH cycle version 6.0, Fig. 2A,B,C), the coupled system produced 156 µM glycolate from 120 µM acceptor molecule (Fig. 2D). Replacing Mco with a methylsuccinyl-CoA dehydrogenase (Mcd), its cognate electron transfer protein (Etf), as well as an Etf-ubiquinone oxidoreductase (creating CETCH cycle version 7.0) further improved glycolate formation from CO2 and light (Fig. S7).

Above results demonstrated that the synthetic CETCH cycle can be functionally coupled to the native energy machinery of photosynthesis in a fully integrated fashion using light energy to form multi-carbon compounds from CO2. Realizing the limitations of individual bulk experiments (e.g., sample volume, self-shading effects, number of parallel assays, and no real-time monitoring), we further envisioned to miniaturize our experimental set-up for parallelization, multiplexing and high-throughput analysis. We therefore developed a droplet-based microfluidic platform for the automated assembly of metabolically active micro-compartments that can be controlled and powered by external illumination and analyzed in real-time (Fig. S8).

In a first step, we encapsulated the TEM into water-in-oil (w/o) micro-droplets (300 pL; 92 µm diameter, Fig. 3A &B) and studied their metabolic activity by assessing NADPH fluorescence in single droplets using microscopy (Fig. S8 andS9). Encapsulating thylakoid membranes produced droplets with a specifically defined number of TEM granules (~100) with a maximum droplet-todroplet variation of 20%, which is expected from a random encapsulation process (Fig. S10B). We further used orthogonal fluorescent barcoding to multiplex different populations of droplets [START_REF] Beneyton | Out-of-equilibrium microcompartments for the bottom-up integration of metabolic functions[END_REF], which allowed us to quantify the local chemical and metabolic states of hundreds of individual droplets of different composition in one experiment in parallel.

We then used multiplexing to study and optimize activity of droplet-encapsulated TEM granules. NADP + photoreduction in droplets was strictly dependent on illumination and directly correlated to the number of TEM granules, following a correlation with chlorophyll content (Fig. 3C & Fig. S11). We observed a maximum photoreduction rate of 2.0 ± 0.1 (95% confidence interval) NADPH µmol min -1 µg -1 Chl at 50 µmol photons m -2 s -1 , which is comparable to rates obtained earlier in bulk experiments. Droplet-to-droplet variation in NADPH production was largely determined by statistical fluctuations of the number of encapsulated TEM granules (Fig. S10C).

We further characterized and optimized the operating conditions of the TEM in micro-droplets.

Sorbitol at 700 mM increased stability of the TEM by several hours (Fig. S11). NADP + photoreduction. increased with higher light intensities from 50 to 200 µmol photons m -2 s -1 , above which NADPH production rates decreased again, likely due to photodamage of the TEM (Fig. S12). NADP + photoreduction was operable and stable over light-dark cycles (Fig. S13, S14D, S15B), demonstrating that the TEM could be switched on and off in individual droplets.

We next tested the capability of TEM-containing droplets to power individual enzyme reactions by co-encapsulation of enzymes and substrates. First, we tested Ghr that catalyzes the NADPHdependent reduction of glyoxylate to glycolate (Fig. 3D). At 120 µg Chl mL -1 reaction mixture, 8.2 µg mL -1 Ghr and 50 µmol photons m -2 s -1 , we observed production of 4.7 mM glycolate (starting from 5 mM glyoxylate and only 0.8 mM NADP + ) after 75 minutes in the light and no production in the dark control. Varying the number of TEM granules, substrate and Ghr concentrations in individual droplet populations resulted in distinct dynamic NADPH equilibrium states (Fig. 3D-F and Fig. S14), reflecting the real-time cofactor production and consumption rates in the different populations of droplets. Light-dark cycles could be used to temporally regulate cofactor regeneration and enzyme kinetics in droplet populations (Fig. 3F).

The homogenous behavior of droplet populations enabled us to subsequently program the metabolic activity of reaction compartments in a predictable fashion. To demonstrate this, we created a patterned emulsion of two populations of droplets differing in TEM as well Ghr concentration. This binary emulsion was activated by illumination, resulting in distinct NADPH production rates, depending on the TEM concentration in the two droplet populations. In a subsequent dark phase, NADPH was consumed at distinct rates that were correlated to different Ghr loading of the two populations (Fig. 3G & movie S3), demonstrating the high level of spatial, temporal, and synchronized control over individual reaction compartments that can be achieved with our platform. Similar results were also obtained for other droplet-encapsulated enzymes that required ATP-and/or NADPH, namely propionyl-CoA synthase (Pcs) and Ccr (Fig. S15 andS16).

With Ccr we measured single-enzyme CO2-fixation rates of 6.4 µmol min -1 mg -1 Chl in droplets.

Without any further optimization, these rates are more than two orders of magnitude higher than recent reports of coupling photosystem II (PSII) reaction centers to pyruvate carboxylase [START_REF] Lee | Photosynthetic artificial organelles sustain and control ATP-dependent reactions in a protocellular system[END_REF], comparable to values reached for PSII-coupled photoelectrochemical hydrogen production (notably without CO2 fixation, ( 5)) and reaching levels measured for isolated chloroplasts (Table S2).

Having created photosynthetic micro-compartments powering single enzyme reactions, we ultimately aimed at encapsulating and screening different variants of the CETCH cycle inside TEM-containing droplets (Fig. 4). After further optimizing the preparation of droplets for enzymes and metabolites of the CETCH cycle (Fig. S17), we encapsulated different CETCH cycle versions together with TEM and monitored the dynamic equilibrium of NADPH. This allowed us to directly quantify the behavior of different CETCH variants in hundreds of micro-compartments side-byside and in real time, which would not have been possible in bulk experiments (Fig. 4B, 4C, & Fig. S18A-B). Droplets with CETCH based on Mcd (version 7.0) maintained TEM activity longer than droplets containing CETCH based on Mco (version 6.0) (Fig. S18). Supply of an additional ATP regeneration module (Ppk and polyphosphate) did not increase activity further (Fig. 4B &C), suggesting that cofactor regeneration was not limiting productivity of our integrated photosynthetic system, but rather the concentration, and/or interplay of the individual components of our system, such as the stability of CoA-thioester intermediates (Fig. S17). Without further optimization, our integrated system was able to produce 47 ± 5 µM glycolate from CO2 over 90 minutes in droplets (Fig. 4D). Thus, while overall productivity of our complex system was lowered compared to Ccr alone, it still outperforms other efforts using only single enzymes [START_REF] Lee | Photosynthetic artificial organelles sustain and control ATP-dependent reactions in a protocellular system[END_REF]. For the full CETCH cycle, we calculated a carbon conversion efficiency of about 3.5% in our microcompartments (NADPH consumption rate of CO2 reduction divided by the measured maximum rate of NADP + photoreduction achieved in droplets). Overall our results demonstrated that it is possible to interface natural and synthetic biological modules in thousands of cell-sized compartments to create new-to-nature photosynthetic entities that have the potential to outcompete natural photosynthesis (i.e. because of a more efficient CO2-fixation metabolism that does not suffer from photorespiration).

The technical capability to reconstruct, control, and study complex reaction networks in a cell-like environment will be of use for both top-down and bottom-up synthetic biology. Prototyping complex metabolic reaction cascades in miniaturized compartments has the potential to provide new means for metabolic engineering. Technical advancements, especially the development of combinatorial screening methods [START_REF] Kulesa | Combinatorial drug discovery in nanoliter droplets[END_REF] and bar-coding techniques to encode reaction conditions in microfluidics-based high-throughput screening [START_REF] Svensson | Coding of Experimental Conditions in Microfluidic Droplet Assays Using Colored Beads and Machine Learning Supported Image Analysis[END_REF] could further enhance multiplexing capabilities and guide future efforts of testing and optimizing the CETCH cycle and other new-tonature pathways prior to their transplantation into living cells.

Our efforts also demonstrate how natural and synthetic biological modules can be mixed and matched us to create highly integrated systems that show life-like functions. Our 'synthetic chloroplast' possesses the essential characteristics of photosynthesis that allow the formation of biological building blocks from inorganic carbon, providing the basis to develop a self-sustained, completely synthetic 'designer' carbon metabolism in our artificial organelle. Future implementation of other life characteristics, such as self-repair, reproduction, as well as information processing and regulatory circuits will further contribute to the realization of synthetic organelles and cells from the bottom-up that approach or even exceed a grade of organization, integration and functional efficiency compared to their natural counterparts (4). bulk curve shows an experiment with the same reaction mixture but on the micro-tube scale, kept in the dark for the duration of droplet manufacture. The bulk solution and the droplets were simultaneously exposed to light for parallel comparison.

T i m e ( m i n ) [ G l y c o l a t e ] / [ s t a r t i n g s u b s t r a t e ]

Materials and Methods

Materials

Chemicals were purchased from Sigma-Aldrich (Munich, Germany) and CARL ROTH GmbH (Karlsruhe, Germany). Sulforhodamine B and 1H, 1H, 2H, 2H-perfluoro-1-octanol were purchased from Sigma. Na 13 CO3H was obtained from Cambridge Isotope Laboratories Inc.

(Tewksbury, USA) and 3-hydroxypropionate was bought from TCI Deutschland GmbH (Eschborn, Germany). Fluoro-silane (Aquapel) was purchased from Aquapel Glass Treatment (Pittsburgh Glass Works LLC Pittburgh, PA, USA). Coenzyme A was purchased from Roche Diagnostics. Biochemicals and materials for cloning and expression were obtained from Thermo Fisher Scientific (St. Leon-Rot, Germany), New England Biolabs GmbH (Frankfurt am Main, Germany), and Macherey-Nagel GmbH (Düren, Germany). Carbonic anhydrase was bought from MP Biomedicals (Illkirch, France). Primers were obtained from Eurofins MWG GmbH (Ebersberg, Germany). Synthesized genes were obtained from Eurofins MWG GmbH (Ebersberg, Germany) or BaseClear B.V. (Leiden, Netherlands). Materials and equipment for protein purification were obtained from GE Healthcare (Freiburg, Germany), Bio-Rad (Munich, Germany) or Merck Millipore GmbH (Schwalbach, Germany). [START_REF] Schwander | A synthetic pathway for the fixation of carbon dioxide in vitro[END_REF][START_REF] Peter | A Chemo-Enzymatic Road Map to the Synthesis of CoA Esters[END_REF]. All CoA-thioesters were purified using a HPLC (1260 Infinity, Agilent Technologies GmbH) with a Gemini® 10µm NX-C18 110 Å Column (Phenomenex, Aschaffenburg, Germany) as described previously [START_REF] Schwander | A synthetic pathway for the fixation of carbon dioxide in vitro[END_REF][START_REF] Peter | A Chemo-Enzymatic Road Map to the Synthesis of CoA Esters[END_REF]. The concentration of CoA-esters was quantified by determining the absorption at 260 nm (ε = 22.4 mM -1 cm -1 for unsaturated and ε = 16.4 mM -1 cm -1 for saturated CoA-thioesters).

CoA-Thioester synthesis

Cloning and Mutagenesis

Chlamydomonas reinhardtii ferredoxin, spinach ferredoxins, and spinach ferredoxin:NADP + oxidoreductase (FNR) lacking the transit peptides were codon optimized for enzyme production in E. coli by Eurofins Genomics Germany GmbH (Ebersberg, Germany). They were cloned into pET16b, pET28b, or pASK-IBA7 with the addition of an N-terminal Strep-tag. A C. reinhardtii

General protein production and purification

Enzymes were produced in Escherichia coli strains BL21(DE3), BL21(DE3) AI, Rosetta 2 (DE3) pLysS, C41(DE3) pLysS pRKisc, and BL21(DE3) ΔiscR. Cells were grown in terrific broth at 37 °C using the appropriate antibiotic for selection (100 µg/ml ampicillin, 50 µg/ml kanamycin, 34 µg/ml chloramphenicol, 20 µg/ml Streptomycin, 10 µg/ml tetracycline, and 50 µg/ml spectinomycin). Unless otherwise noted, when an OD600 = 0.7-1.0 was reached the culture was cooled to 23°C and induced by the addition of 500 μM IPTG (Isopropyl-D-βthiogalactopyranoside) or 200 μg/L anhydrotetracycline. When using E. coli BL21(DE3) AI as an expression host 0.02 % (w/v) L-arabinose was additionally added. After 14-18 hours the cells were harvested for 12 min at 6,600 × g at 4 °C. Unless immediately purified, cell pellets were frozen [START_REF] Schwander | A synthetic pathway for the fixation of carbon dioxide in vitro[END_REF]. However, the resulting protein solution was flash frozen and stored at -80°C. This increased the stability of some of the enzymes from days or weeks to months [START_REF] Schwander | A synthetic pathway for the fixation of carbon dioxide in vitro[END_REF]. Codon optimized propionyl-CoA synthase (Pcs) was produced and purified according to Bernhardsgrütter et al. [START_REF] Bernhardsgrütter | Awakening the Sleeping Carboxylase Function of Enzymes: Engineering the Natural CO2-Binding Potential of Reductases[END_REF].

Recombinant protein production and purification of Chlamydomonas and Spinach ferredoxins

Ferredoxins were produced in C41(DE3) pLysS pRKisc, or BL21(DE3) ΔiscR cultures were grown to an OD600 of 0.7-0.9 and cooled to 23 °C and induced by the addition of 500 μM IPTG and ammonium ferric citrate was added (260 mg per liter of growth media). Cells were harvested after 14-18 h as described above. Cell pellets were resuspended in a lysis buffer (50 mM HEPES-KOH pH 7.8, 150 mM NaCl, 2 mM DTT, and 10% glycerol) at 2 mL per gram of pellet. The cells were lysed and clarified as above. The supernatant was loaded onto a StrepTrap HP (GE Healthcare, Freiburg, Germany) equilibrated with the lysis buffer or a buffer without the glycerol.

The unbound protein was washed with the same buffer. Elution was carried out in the same buffer with the addition of 2.5 mM desthiobiotin. The resulting protein was concentrated as described above, but quantified using the following extinction coefficients: Chlamydomonas ferredoxin, 8.38 mM cm -1 at 420 nm [START_REF] Galván | Physicochemical Properties of Ferredoxin from Chlamydomonas reinhardii[END_REF]; Spinacia oleracea ferredoxin, 9.68 mM cm -1 at 420 nm [START_REF] Tagawa | Oxidation-reduction potentials and stoichiometry of electron transfer in ferredoxins[END_REF].

Recombinant protein production and purification of Chlamydomonas and Spinach Ferredoxin NADP + reductase (FNR) Strep-tagged FNR from both S. oleracea and C. reinhardtii were produced in BL21(DE3) as described above. Cells were lysed in a buffer containing 50 mM HEPES-KOH pH 7.8, 150 mM NaCl, and 10% glycerol. Lysis and clarification were performed as above and loaded onto a StrepTrap HP (GE Healthcare, Freiburg, Germany). It was washed with a buffer containing 50mM HEPES-KOH pH 7.8 and 150 mM NaCl and eluted in a buffer containing 2.5-5 mM desthiobiotin.

The protein was concentrated in an Amicon and 40% glycerol was added as a cryoprotectant prior to freezing. The concentration for both C. reinhardtii and Spinach FNR were determined using the extinction coefficient, 10.74 mM cm -1 at 456 nm (40).

Electron transport flavoprotein-oxidoreductase (ETF:QO) protein production and purification ETF:QO enzymes were produced in BL21(DE3) or C41(DE3) harboring both the pLysS, and the pRKisc plasmid for iron-sulfur cluster formation [START_REF] Nakamura | Hyperproduction of Recombinant Ferredoxins in Escherichia coli by Coexpression of the ORF1-ORF2-iscS-iscU-iscA-hscB-hscA-fdx-ORF3 Gene Cluster1[END_REF]. Cells were grown, induced, and harvested according to the basic protocol above. The enzyme was purified based on a modified method from Usselman et al. [START_REF] Usselman | Impact of Mutations on the Midpoint Potential of the [4Fe-4S]+1,+2 Cluster and on Catalytic Activity in Electron Transfer Flavoprotein-ubiquinone Oxidoreductase (ETF-QO)[END_REF]. Cell pellets were resuspended in 1:3 ratio (w/v) in buffer A (50 mM Tris-HCl pH 7.6, 500 mM NaCl, and 0.1 mM DTT), prior to lysis and 10 µg/mL DNAseI was added. Cells were lysed by French press or ultrasonication and the insoluble fractions were harvested by ultracentrifugation for 1 hour at 100,000 × g. The supernatant was removed and the resulting pellet was washed in buffer A and centrifuged again. A rough protein concentration of the pellet was determined with the Pierce™ Rapid Gold BCA Protein assay kit (Thermo Scientific). The pellet was resuspended in buffer A to approximately 20 mg protein/mL. The pellet was solubilized by adding dodecyl-β-D-maltoside at a ratio of 2.5:1 (w/w) of protein to dodecylβ-D-maltoside and shaking for 90 minutes at 8°C. The solution was centrifuged for a third time for 1 hour at 100,000 × g and the resulting supernatant was diluted 10-fold in buffer A, filtered with a 0.45 µm syringe filter, and loaded onto a StrepTrap HP or HisTrap FF (rsETF:QO and pmETF:QO, respectively). The washing and elution of the enzymes was done according to the protocols above for His and Strep-tagged proteins.

Chloroplast Isolation

Chloroplasts were isolated from young spinach purchased from the local market or grocery store using a modified method from [START_REF] Strand | The higher plant plastid NAD(P)H dehydrogenase-like complex (NDH) is a high efficiency proton pump that increases ATP production by cyclic electron flow[END_REF][START_REF] Seigneurin-Berny | Purification of Intact Chloroplasts from Arabidopsis and Spinach Leaves by Isopycnic Centrifugation[END_REF]. Spinach leaves were stored in the dark at 4-8 °C until use. The leaves were washed and the large stems were removed and buffer was added at a ratio of 1 g plant material to 1 mL cold buffer (330 mM sorbitol, 50 mM HEPES-KOH pH 7.6, 5 mM MgCl2, 0.1% (w/v) bovine serum albumin) and blended using a standard kitchen immersion blender. The resulting solution was pressed through a piece of fine mesh cotton fabric and the filtrate was centrifuged for 10 min at 3000 × g. The pellet was gently resuspended in buffer (300 mM sorbitol, 50 mM HEPES-KOH pH 7.6, 5 mM MgCl2, 2 mM EDTA, and 10 mM sodium Lascorbate,), using a fine paint brush to remove any clumps. This was overlaid on an 80/40% percoll gradient (80%: 80% v/v percoll, 10 mM sodium L-ascorbate, 300 mM sucrose, 66 mM MOPS-KOH pH 7.6 and 40%: 40% v/v percoll, 10 mM sodium L-ascorbate, 300 mM sucrose, 25 mM MOPS-KOH pH 7.6). The fractions containing thylakoids and intact chloroplasts were pooled and diluted in buffer and centrifuged for 10 min at 3000 × g. The pellet was resuspended in osmotic shock buffer (10 mM HEPES-KOH, 10 mM MgCl2, 10 mM sodium L-ascorbate). Thylakoids were flash frozen with 10% DMSO as an osmoprotectant and stored at -80°C until use. The thylakoid/chloroplast solutions were maintained in darkness.

Before use, thylakoids were stored on ice and washed 2-3 times in a buffer containing: 0, 330, or 700 mM sorbitol, 10 mM HEPES-KOH pH 7.6, 10 mM MgCl2, and 10 mM sodium L-ascorbate.

The chlorophyll content of the resulting solution was determined according to Porra 2002 (44).

Assays of Thylakoid activity

Spectrophotometric observation of NADP + photoreduction and the ferredoxin titration.

TEM activity was assayed by monitoring NADPH production spectrophotometrically in a 5 mm quartz cuvette at 340 nm on a UV-Vis spectrophotometer (Cary 60 UV-Vis, Agilent Technologies GmbH). In a reaction volume of 0.7 mL, TEM was added to reach a total of 10 µg of chlorophyll to a reaction buffer containing: 50 mM HEPES-KOH pH 7.8, various ferredoxin concentrations, 3 mM ADP, 5 mM of K2HPO4, 3mM NADP + , 10 mM sodium L-ascorbate, 10 mM KCl, 5 mM MgCl2, 1.5 µM E. coli catalase, and 52 U mL -1 of bovine superoxide dismutase and illuminated with white light at 50-100 µmol photons m -2 s -1 . Initially, various ferredoxins (SpFdx1, SpFdx2, & CrFdx1) were tested with minimal differences in activity. Ultimately, for the ferredoxin titration 0, 2.5, 5, 10, 25, and 50 µM of CrFdx1 was assayed. The concentration of NADPH was calculated using an extinction coefficient of 6.22 mM cm -1 .

ATP/NADPH ratio

The ATP/NADPH production ratio was determined using a similar reaction mixture (0.7 mL) listed above, with the inclusion of 700 mM sorbitol. The NADPH production was monitored spectrophotometrically in a 5 mm quartz cuvette at 340 nm on a UV-Vis spectrophotometer (Cary 60 UV-Vis, Agilent Technologies GmbH) and the concentration was determined. To trigger TEM activity, a white light was used at 60 µmol photons m -2 s -1 . Samples for ATP measurements were taken at 0, 5, 15, 30 minutes after illumination and quenched with 5% formic acid. The samples were immediately measured by HPLC-MS as described below. The concentrations were calculated using a standard curve. Standard solutions were made using commercially available ATP prepared in a buffer reflective of assay conditions for accurate concentration calculation.

ATP production rate

The ATP production rate was determined in a reaction buffer (0.2 mL) containing: 50 mM HEPES-KOH pH 7.6, 10 mM sodium L-ascorbate, 700 mM sorbitol, 5 mM MgCl2, 5 mM K2HPO4, 10 mM KCl, 5 µM of CrFdx1, 2 mM NADP + , 2 mM ADP, 1.5 µM of catalase, and 52 U mL -1 of bovine superoxide dismutase, and if DAPP was added, it was at 20 µM. Thylakoids were added at 2.5 µg and 10 µg chlorophyll and assayed both in the dark and in the light at 60-70 µmol photons m -2 s -1 . Samples were taken at 0, 5, 10, and 15 minutes and quenched with a final concentration of formic acid of 5%. ATP was measured with HPLC-MS by the method described below. The concentrations were calculated using a standard curve. Standard solutions were made using commercially available ATP prepared in a buffer reflective of assay conditions for accurate concentration calculation.

Oxygen evolution and NADPH production

Simultaneously, the rates of O2 evolution and NADPH production were measured in an assay volume of 0.7 mL in a reaction buffer containing: 50 mM HEPES-KOH pH 7.6, 10 mM sodium L-ascorbate, 700 mM sorbitol, 5 mM MgCl2, 5 mM K2HPO4, 10 mM KCl, 5 µM of CrFdx1, 3 mM NADP + , 2 mM ADP, 1.5 µM of catalase, 52 U mL -1 of bovine superoxide dismutase, and 30 µM DAPP. Thylakoids were added at a total of 10 µg chlorophyll and assayed both in the dark and in the light at 60-70 µmol photons m -2 s -1 . NADPH production was measured as discussed above.

The O2 evolution was measured with a PyroScience fiber optic oxygen probe, either an optically isolated minisensor (OXF1100-OI) or microsensor (OXF50-OI). The NADPH production was measured in a spectrophotometer in a 5mm quartz cuvette at 340 nM. A decrease of O2 was observed in reaction mixtures that lacked thylakoids, and this was used for a baseline correction of samples.

Oxygen evolution at different light intensities or with and without catalase and SOD

The O2 evolution was measured at different light intensities with a PyroScience fiber optic oxygen probe, either an optically isolated minisensor (OXF1100-OI) or microsensor (OXF50-OI).

The rates were measured in an assay volume of 0.4 mL in a reaction buffer containing: 50 mM HEPES-KOH pH 7.6, 10 mM sodium L-ascorbate, 700 mM sorbitol, 5 mM MgCl2, 5 mM K2HPO4, 10 mM KCl, 5 µM of CrFdx1, 3 mM NADP + , 2 mM ADP, either with or without 1.5 µM of catalase, and 52 U mL -1 of bovine superoxide dismutase. Thylakoids were added at a total of 10 µg chlorophyll and assayed both in the dark, 30, 60, or 300 µmol photons m -2 s -1 . There was a decrease in O2 levels in the dark and this decrease was subtracted from the samples in the light.

Oxygen evolution during Carbon fixation

The O2 production from TEM during the fixation of carbon (by Ccr and Pcc) was measured in an assay volume of 0.5 mL. The reaction mixture was comprised of 50 mM HEPES-KOH pH 7.6, 10 mM sodium L-ascorbate, 700 mM sorbitol, 5 mM MgCl2, 5 mM inorganic phosphate (K2HPO4), 10 mM KCl, 5 µM of CrFdx1, 0.6 mM Propionyl-CoA, 1 mM Crotonyl-CoA, 1 mM NADP + , 0.5 mM ADP, 30 nM carbonic anhydrase, 1.5 µM of catalase, 52 U mL -1 of bovine superoxide dismutase, 1.3 µM Ccr, and 1.8 µM Pcc, and 30 µM DAPP. Thylakoids were added at a rate of 7.5µg total chlorophyll. The reactions were assayed, both in the dark and illuminated at 60-70 µmol photons m -2 s -1 . O2 was measured using the PyroScience fiber optic oxygen probe with either an optically isolated minisensor (OXF1100-OI) or microsensor (OXF50-OI). There was a decrease in O2 levels in the dark and this was used as a baseline correction. To measure product formation from Pcc or Ccr, samples were taken at 0, 2, and 5 minutes and quenched with formic acid (final concentration of 5%) and analyzed by HPLC-MS using the method described below.

Concentrations were calculated using a standard curve prepared in a solution of quenched, unreacted reaction mixture.

CETCH assays

Assay of CETCH

The initial photoCETCH cycle experiments were performed in 270 µl reaction volume with thylakoids added at 125 µg Chl/mL in a buffer containing: 50 mM HEPES, 330 mM Sorbitol, 10 mM sodium L-ascorbate, 100 µM coenzyme B12, 80 µM propionyl-CoA, 1.25 mM ADP, 2 mM NADP + , 5 mM MgCl2, 5 mM K2HPO4, 10 mM KCl, 50 mM NaH 13 CO3, 1.2 µM catalase, 310 nM superoxide dismutase, 5 µM FdxCr, 1.3 µM Ghr, and the core enzymes from CETCH v6.0 (listed in Supplemental Table 3). Samples (30 µL) were taken at 0, 5, 15, 30, 45, 60, 90 and 120 minutes and quenched with formic acid at a final concentration of 5 %. The CoA esters were measured using an Agilent 6550 iFunnel Q-TOF LC-MS as described below. The glycolate produced was derivatized and measured by UPLC-MS/MS (using Agilent 6495B Triple Quad LC/MS) as described below. The glycolate was quantified using a standard curve. Standard solutions were prepared in a quenched, unreacted reaction mixture.

Assay of CETCH v6.0 with Ghr

CETCH cycle v6.0 was reacted in 300 µL with thylakoids added at 125 µg Chl/mL in a buffer containing: 50 mM HEPES-KOH, 330 mM Sorbitol, 10 mM sodium L-ascorbate, 100 µM coenzyme B12, 80 µM propionyl-CoA, 1.25 mM ADP, 2 mM NADP + , 5 mM MgCl2, 5 mM K2HPO4, 10 mM KCl, 50 mM NaH 13 CO3, 1.2 µM catalase, 310 nM superoxide dismutase, 5 µM FdxCr, 1.3 µM Ghr, and the core enzymes from CETCH v6.0 (listed in Supplemental Table 3). Samples (30 µL) were taken at 0, 5, 15, 30, 45, 60, 90 and 120 minutes and quenched with formic acid at a final concentration of 5 %. The CoA esters were measured using an Agilent 6550 iFunnel Q-TOF LC-MS as described below. The glycolate produced was derivatized and measured by UPLC-MS/MS (using Agilent 6495B Triple Quad LC/MS) as described below. The glycolate was quantified using standard curve. Solutions were prepared in a quenched, unreacted reaction mixture.

Assay of CETCH v7.0 CETCH cycle v7.0 was reacted in 300 µL with TEM added at 210 µg Chl/mL in a buffer containing: 50 mM HEPES-KOH, 700 mM Sorbitol, 10 mM sodium L-ascorbate, 100 µM coenzyme B12, 85 µM propionyl-CoA, 0.5 mM ADP, 2 mM NADP + , 5 mM MgCl2, 5 mM K2HPO4, 10 mM KCl, 50 mM NaH 13 CO3, 1.2 µM catalase, 310 nM superoxide dismutase, 5 µM FdxCr, 1.3 µM Ghr, and the core enzymes from CETCH v7.0 (listed in Supplemental Table 3). Samples (30 µL) were taken at 0, 5, 15, 30, 45, 60, 90 and 120 minutes and quenched with formic acid at a final concentration of 5 %. The CoA esters were measured using an Agilent 6550 iFunnel Q-TOF LC-MS as described below. The glycolate produced was derivatized and measured by UPLC-MS/MS (using Agilent 6495B Triple Quad LC/MS) as described below. The glycolate was quantified using a standard curve. Standard solutions were prepared in a quenched, unreacted reaction mixture.

Optimization of CETCH v7.0 for droplets CETCH cycle v7.0 was reacted in 300 µL with TEM added at 126 µg Chl/mL in a buffer containing: 50 mM HEPES-KOH, 700 mM Sorbitol, 10 mM sodium L-ascorbate, 85 µM crotonyl-CoA or propionyl-CoA, 0.5 mM ADP, 2 mM NADP + , 5 mM MgCl2, 5 mM K2HPO4, 10 mM KCl, 50 mM NaH 13 CO3, 1.2 µM catalase, 310 nM superoxide dismutase, 5 µM FdxCr, 1.3 µM Ghr, and the core enzymes from CETCH v7.0 (listed in Supplemental Table 3). Ecm and Mcm were incubated with 2 µl of a buffered solution of 5 mM coenzyme B12 for 30 minutes in the dark and at room temperature prior to adding the enzymes to the reaction mixture. Some samples included the addition of PhaJ (14 µM) and some reactions were incubated for 1 hour prior to illumination.

The samples (30 µL) were taken at 0, 5, 15, 30, 45, 60, 90 and 120 minutes and quenched with formic acid at a final concentration of 5 %. The CoA esters were measured using an Agilent 6550 iFunnel Q-TOF LC-MS as described below. The glycolate produced was derivatized and measured by UPLC-MS/MS (using Agilent 6495B Triple Quad LC/MS) as described below. The glycolate was quantified using a standard curve. Standard solutions were prepared in a quenched, unreacted reaction mixture.

Quantification of reaction products

High Resolution LC-MS/MS of CoA Esters

Compounds were separated on a RP-18 column (50 mm x 2.1 mm, particle size 1.7 µm, Kinetex EVO C18, Phenomenex) using a mobile phase system comprised of 50 mM ammonium formate pH 8.1 (A) and methanol (B). Chromatographic separation was carried out using the following gradient condition at a flow rate of 250 µL/min: 0 min 2.5% B; 2.5 min 2.5% B; 8 min 23% B; 10 min 80 %B; 11 min 80%; 12 min 2.5% B; 12.5 min 2.5% B. The column oven was set to 40 °C and autosampler was maintained at 10 °C. Standard injection volume was 1 µL.

CoA esters were analyzed using an Agilent 6550 iFunnel Q-TOF LC-MS system equipped with an electrospray ionization source set to positive ionization mode.

Capillary voltage was set at 3.5 kV and nitrogen gas was used as nebulizing (20 psig), drying (13 L/min, 225 °C) and sheath gas (12 L/min, 400°C). The TOF was calibrated using an ESI-L Low Concentration Tuning Mix (Agilent) before measurement (residuals less than 2 ppm for five reference ions) and was recalibrated during a run using 922 m/z as reference mass . The scan range for MS data is 500-1200 m/z. Alternatively, the CoA esters were detected using an Agilent 6495B Triple Quad LC/MS system equipped with an electrospray ionization source. The source conditions were identical to that of the QTOF conditions. Data were acquired in the positive MRM mode with collision energy, LC-MS data were analyzed using MassHunter Qualitative Navigator and QQQ Quantitative analysis software.

UPLC-MS/MS analysis of derivatized glycolate

Glycolate was derivatized according to the method published by Han et al. [START_REF] Han | Metabolomic analysis of key central carbon metabolism carboxylic acids as their 3-nitrophenylhydrazones by UPLC/ESI-MS[END_REF]. Briefly described, 50 μl of sample was mixed with 50 μL 150 mM 1-(3-Dimetheylaminopropyl)-3ethylcarbodiimide (EDC), 50 μl 250 mM 3-nitrophenylhydrazine (3-NPH), and 50 μl of 7.5% pyridine in methanol in a 1.5 ml Eppendorf tube. The reaction was incubated at 30°C for 30 min.

After incubation, the samples were centrifuged at 13,000 x g for 1 min and the supernatant transferred into HPLC vials. UPLC-MS/MS analyses were performed on an Agilent 6495B Triple Quad LC/MS system equipped with an electrospray ionization source.

The analytes were separated on a RP-18 column (50 mm x 2.1 mm, particle size 1.8 µm, ZORBAX RRHD Eclipse Plus C18, Agilent) kept at 40 °C using a mobile phase system comprised of 0.1% formic acid in water (A) and acetonitrile (B). The gradient is as follows: 0 min 5% B; 1 min 5% B, 6 min 95% B; 6.5 min 95% B; 7 min 5 %B at a flow rate of 250 µL/min. Samples were held at 15°C and injection volume was 5 µL. MS/MS data were acquired in negative MRM mode. Capillary voltage was set at 3 kV and nitrogen gas was used as nebulizing (25 psig), drying (11 L/min, 130 °C) and sheath gas (12 L/min, 400°C). The dwell time and fragmentor voltage were 20 ms and 380 V respectively. Optimized collision energy used for the both quantifier (210 m/z  137 m/z) and qualifier (210 m/z  152 m/z) and was 22 V. LC-MS data were analyzed and quantified using MassHunter Qualitative Navigator and QQQ Quantitative Analysis softwares (Agilent).

UPLC-MS/MS analysis of ATP, ADP, and AMP

UPLC-MS/MS analyses were performed on an Agilent 6495B Triple Quad LC/MS system equipped with an electrospray ionization source.

The analyte was separated on a HILIC column (50 mm x 2.1 mm, particle size 1.7 µm, 130 Å, BEH Amide, Waters) using a mobile phase system comprised of 95:5 20 mM ammonium acetate pH 9.3 / acetonitrile (A) and acetonitrile (B). The compounds were eluted through the column at a flow rate of 400 µL/min under the following conditions: 0 min 90% B, 1.5 min 40% B, 1.8 min 40% B, 1.9 min 90 %B, 2.5 min 90% B. Samples were held at 15°C and injection volume was 1 µL. MS/MS data were acquired in negative MRM mode. Capillary voltage was set at 3.5 kV and nitrogen gas was used as nebulizing (20 psig), drying ( LC-MS data were analyzed and quantified using MassHunter Qualitative Navigator and QQQ Quantitative Analysis softwares (Agilent).

Microfluidic device fabrication and operation

Dropmaker devices (fig. S8) were made of poly(dimethylsiloxane) (PDMS, Sylgard 184) from a SU8-3000 negative photoresist (MicroChem Corp) mold (30 µm depth) produced using a standard soft-lithography procedure [START_REF] Beneyton | CotA laccase: highthroughput manipulation and analysis of recombinant enzyme libraries expressed in E. coli using droplet-based microfluidics[END_REF]. Microfluidic channels were treated using fluoro-silane (Aquapel, Aquapel) before use. Nemesys syringe pumps (Cetoni) were used to control the flows in the microfluidic channels. Devices were connected to pumps with PTFE tubing (Fischer Scientific, ID 0.3 mm, OD 0.76 mm). Droplets were produced in fluorinated oil (Novec®3000, 3M) and stabilized against coalescence by a perfluoropolyether-polyethyleneglycol blockcopolymer surfactant (Fluosurf, Emulseo).

A microfluidic 2D-chamber (fig. S8) was assembled as previously described [START_REF] Beneyton | Out-of-equilibrium microcompartments for the bottom-up integration of metabolic functions[END_REF]. Briefly, the chamber geometry (35 mm x 10 mm) was cut in a 60 µm-thick double-sided bonding tape (1375, SDAG Adhésifs) using a Graphtech cutting plotter (CE 6000-40). The double-sided bounded template was sandwiched between two microscopy glass slides (76 x 25 x 1mm, Mareinfeld). Holes and glued nanoports on the top glass slide served as inlet/outlet. The chambers were treated using fluoro-silane (Aquapel, Aquapel) before use.

Thylakoid encapsulation

Independently from final composition, thylakoids suspensions were flowed (100 µL/h) in the dropmaker device and flow-focused with two streams of fluorinated oil containing 3 wt% surfactant (225 µL/h). In typical experiments, 4-bit emulsions were produced by encapsulating four different mixtures in parallel. The 4-bit emulsions were barcoded with sulforhodamine B fluorophore (2, 8, 16, 40 µM). Droplets were collected together in a PTFE tubing and directed to the 2D-chamber. Once the 2D-chamber was fully loaded, flows were stopped and the 2D-chamber closed with caps. Specific assay mixtures can be found in the tables below.

Time-lapse fluorescence measurements

The 2D-chamber device was mounted on the stage of an inverted microscope equipped with light emitting diodes (fig. S8). A 365 nm diode (1150 mW, Thorlabs) combined to an epifluorescence cube composed of an excitation bandpass filter (F39-370, AHF), a beamspliter (F38-409, AHF) and an emission bandpass filter (F39-438, AHF) was used for measuring NADPH fluorescence. A 550 nm diode (CoolLED pE-2) was used for measuring sulforhodamine B fluorescence. A warm white light emitting diode (2000 mW, Thorlabs) mounted on the stage of the microscope was used for the light-activation of the thylakoids. Images were taken with a digital camera (EOS 600, Canon). A labVIEW routine triggering the white LED, the 365 nm LED, and the digital camera was used to perform the time lapse experiments with defined light and imaging patterns.

Image processing

The home-made image processing algorithm consists of a three-step procedure to automatically extract information from every image captured during the time-lapse experiment (fig. S9). (i) A region of interest is drawn on the brightfield image to select the droplets of interest and discard droplets located in the image corners. Using the brightfield image, an intensity threshold is applied in order to discriminate the edges of the droplets to the background of the image. Then, the brightfield image is converted into a binary image where the edges of the droplets are only displayed. From this binary image, droplet boundaries are detected using the Hough transform procedure. The detection of droplets is limited to the range of a low and high radius in order to reduce the time processing. The Hough transform procedure outputs radius and the locations of droplets in the region of interest. The data are saved and the image processing algorithm automatically moves to the coding image. (ii) The coding image is captured at the same location as the brightfield image. Consequently, the droplet location and radius data can be used to find every droplet of interest in the coding image. The fluorescence intensity of each droplet is obtained by listing the intensity value of all pixels composing the droplets tested. The median value of the pixel intensity for each droplet is saved and characterizes the coding intensity of the droplet tested. This process is repeated for every droplet in the imaged region of the interest. Then the image processing algorithm moves to the time lapse images. (iii) Every time lapse image is processed using the same method as the coding image step (ii). Briefly, the median value of the fluorescence intensity of every pixel composing a droplet is saved. Then, this process is iterated for every droplet and image composing the time lapse. The LabVIEW code used for image analysis has been uploaded to a repository on GitHub [START_REF]Data and computational codes are available[END_REF].

Large-scale experiments 1-bit emulsions (contents outlined below) were produced in large quantities (~500 µL, ~10 8 droplets) and collected in a 2 mL glass vial. The glass vial was continuously rotated and illuminated with warm white LED. 30 µL of emulsion was regularly sampled from the vial and coalesced as follows: the droplets were added to 50 µL of fluorinated oil; 20 µL of 1H, 1H, 2H, 2H-perfluoro-1-octanol was added and the mixture was vortexed and centrifuged; and the aqueous phase was pipetted and quenched with 1% of HCl.

Ccr and Ghr in 1-bit emulsions TEM powered reactions Ghr and Ccr in droplets were assayed in a buffer containing the following: 100 mM HEPES-KOH, pH 7.8, 330 mM sorbitol, 5 mM K2HPO4, 10 mM KCl, 5 mM MgCl2, 10 mM sodium L-ascorbate, 5 µM ferredoxin, 52 U mL -1 superoxide dismutase, 1.2 µM catalase, 1.6 mM ADP, 0.8 mM NADP + , 120 µg Chl mL -1 of TEM, and 8 µM Sulforhodamine B.

To assay Ccr: 255 nM Ccr, 33.5 nM carbonic anhydrase, 1 mM Crotonyl-CoA, and 50 mM NaHCO3 was added. To assay Ghr: 214 nM GhrB and 5 mM glyoxylate was added. Droplets were created from a solution with a total volume of 500 µL. Samples were taken after 75 minutes of illumination at 50 µmol photons m -2 s -1 and quenched as described above. To assess Ccr activity CoA-thioesters were measured by HPLC-MS as described above and quantified using a standard curve. Ghr activity was assessed by measuring glycolate produced by HPLC-MS. The concentration was determined using a standard curve. Standard solutions were prepared in a buffer reflective of assay conditions for accurate concentration calculation.

Light intensity

The effect of light intensity in NADPH production on the droplets was assayed using light intensities at 50, 100, 200, 400 and 1200 µmol photons m -2 s -1 (fig. S12). Two populations of droplets were created from solutions of 0.5 mL that contained: 100 mM HEPES-KOH, pH 7.8, 330 mM sorbitol, 3 mM K2HPO4, 10 mM KCl, 5 mM MgCl2, 10 mM sodium L-ascorbate, 5 µM

Thylakoid consistency in droplets

The consistency between independently prepared droplets was tested using droplets manufactured from four independently pipetted 0.5 mL solutions (fig. S9C &S10C). The four populations contained: 50 mM HEPES-KOH, pH 7.8, 700 mM sorbitol, 5 mM K2HPO4, 10 mM KCl, 5 mM MgCl2, 10 mM sodium L-ascorbate, 5 µM Ferredoxin, 52 U mL -1 superoxide dismutase, 1.2 µM catalase, 1.6 mM ADP, and various concentrations of sulforhodamine B, thylakoids, NADPH, and NADP + . Population 1, 2, and 3 contained: 1.0 mM NADP + , 125 µg Chl mL -1 of thylakoids, and either 2, 8, 20 µM sulforhodamine B. In population 4, thylakoids were omitted and 1 mM NADPH was used instead of NADP + , for the coding dye 40 µM was used.

Droplets were prepared and monitored as discussed above.

Controlling Droplets

Various enzyme and substrate concentrations were used in multiplexed experiments (4-bit, Fig. 3E, S14B, &S14C). In each case the TEM was coupled to Ghr and either various enzyme and/or substrate concentrations were assayed. The specific reaction conditions are shown in Table S4. The droplets were manufactured and monitored as discussed above from 0.5 mL solutions.

Ghr and Ccr in droplets

Both 330 and 700 mM sorbitol conditions were tested with coupling Ccr and Ghr. In each case, four populations were tested either with 330 or 700 mM sorbitol (Fig. 3F, S14D, &S15B).

The specific reaction conditions are shown in Table S5. The droplets were manufactured and monitored as discussed above from 0.5 mL solutions. The contents of each droplet population is indicated and a grey box indicates that component was omitted from that population.

Pcs in droplets

The specific reaction conditions to test Pcs coupling is shown in Table S6 (fig. S16). The four populations of droplets were manufactured and monitored as discussed above from 0.5 mL solutions. The contents of each droplet population is shown and a grey box indicates that component was omitted from that population.

Time and space control of droplets 2-bit emulsion

As a demonstration of the controllability of droplets, both in time and space, a binary emulsion was created (Fig. 3G). The two population of droplets were created using 0.5 mL solutions. The two populations contained 50 mM HEPES•KOH, pH 7.8, 700 mM sorbitol, 5 mM K2HPO4, 10 mM KCl, 5 mM MgCl2, 10 mM sodium L-ascorbate, 5 µM Ferredoxin, 52 U mL -1 superoxide dismutase, 1.2 µM catalase, 1.2 mM ADP, 0.8 mM NADP + , 10 mM glyoxylate, and two different concentrations of GhrA, thylakoids, or sulforhodamine B. Either: 40 nM GhrA, 200 µg Chl mL -1 thylakoids, and 2 µM sulforhodamine B or 2.5 nM GhrA, 40 µg Chl mL -1 thylakoids, and 8 µM sulforhodamine B.

Fig. S1. Characterization, stability and stoichiometry of light-driven ATP and NADPH regeneration by thylakoid membrane-based energy modules (TEMs).

(A) NADP + photoreduction: Titration of ferredoxin concentrations. NADPH production is dependent upon the addition of external ferredoxin. The highest rates of NADP + photoreduction were achieved with the addition of ferredoxin between 2.5-10 µM. Shown are representative examples of NADPH production rates at 100 µmol photons m -2 s -1 , 10 µg total chlorophyll a + b (Chl) and varying ferredoxin concentrations. (B) NADP + photoreduction by photosynthetic membranes NADPH production rate normalized to µg of Chl (line is the mean value with shaded area corresponding to ± standard deviation, N = 6). Rate of NADP + photoreduction was determined from the first minute after the light had been turned on (100 µmol photons m -2 s -1 ). (C) Light-driven ATP formation and dark-control in the presence of the adenylate kinase inhibitor DAPP (teal and grey, respectively; open circles indicate samples with DAPP added). The addition of DAPP decreases ATP formation both in the dark and in the light (lines shown are linear fits, 2 biological replicates, 60-70 µmol photons m -2 s -1 ), presumably due to inhibition of the background reaction of membrane-bound adenylate kinase. (D) Stability of TEMs in the dark: NADPH production of TEM were maintained in the dark for 1 and 2 hours (at room temperature) or 6, 24, and 48 hours, respectively (at 0 ℃, 60 µmol photons m -2 s -1 ). (E) Reproducibility of TEM preparations: NADPH production rates of TEMs are consistent between different thylakoid preparations. Two replicate experiments from two different thylakoid preparations are shown (at 23 ℃, 60 µmol photons m -2 s -1 ). (F) Stoichiometry of cofactor regeneration: ATP (solid lines) and NADPH (dashed lines) production in the presence (coral triangles) and absence of DAPP (blue circles), and the calculated ATP to NADPH ratio at 15 and 30 minutes after light exposure (60 µmol photons m -2 s -1 ). (E) A similar experiment as in (D) but an even lower light condition is shown. All conditions contained SOD and catalase. At 30 µmol m -2 s -1 the O2 evolution was slower but was maintained longer.

Fig. S3. Initial experiments to couple the CETCH cycle to TEM (in bulk).

To couple the CETCH cycle to TEM, enzymes of the CETCH cycle plus Ghr from E. coli were mixed with TEM. Propionyl-CoA was added and the reaction mixture was illuminated (100 µmol photons m -2 s - 1 ). Operation of the CETCH cycle was assessed by following the 13 C-labelling patterns (see fig. S4) and CETCH cycle metabolites methylmalonyl-CoA and ethylmalonyl-CoA as previously described (2). (A-B) Labelling pattern of CETCH v6.0 coupled to TEM (50 µg Chl mL -1 ) starting with 150 µM propionyl-CoA. Both conditions were supplemented with an addition of 10 µM ferredoxin-NADP + reductase (FNR), with added 15 µM FAD (1:1.5 molar ratio, for the contribution of FAD and FNR on the system, see fig. S6). Very little difference between the light (A) and dark (B) operated cycles was observed and ethylmalonyl-CoA was only detected after 60 minutes in the light and not detected in the dark. Table S1.

Carbon fixation and ATP and NADPH regeneration rates of natural and synthetic systems compared to rates achieved in this study (normalized per mg chlorophyll).

Listed are CO2-fixation, ATP and NADPH generation rates of isolated chloroplasts and thylakoids, other synthetic systems and the system of this study. For single-enzyme CO2-fixing reactions (Ccr and Pcc), our integrated system is capable of fixing CO2 at 124 µmoles mg Chl -1 h -1 , which is within the range of natural systems (38-280 µmoles mg Chl -1 h -1 ). In bulk experiments with isolated thylakoids, NADPH and ATP regeneration rates are better than previously reported, yet lower than those measured with intact chloroplasts. In droplets, the regeneration of NADPH is of similar magnitude. Note that these rates are dependent on light intensity and could be improved by using higher light intensities. Furthermore, for the CETCH cycle operation, TEM is added in amounts so that cofactor regeneration is not limiting. Limiting the TEM would improve the rates on a per chlorophyll basis. * Calculated from the O2 evolution assuming for every 1 O2 generated there are 2 NADPH and 3 ATP produced ** From the carbon fixation rates in bulk of single carboxylation reactions † TEM was added in excess. On a per Chl or PSII basis, we expect higher rates when thylakoids are limiting. ‡ Calculated with the NADPH production or from the NADPH dependent reaction, assuming a 2:1 ratio NADPH:O2 ‡ ‡ Calculated with NADPH dependent reactions, 4 NADPH consumed per glycolate formed, assuming a 2:1 ratio NADPH:O2

Reported rates (µmoles/mg

Table S2.

Comparison of carbon fixation and ATP regeneration rates of natural and synthetic systems compared to rates achieved in this study normalized to the chromophore.

Reported CO2-fixation rates of natural and synthetic systems compared to rates achieved in this study. As above, rates of TEM-powered single CO2 fixation reactions (68,600 molecules PSII -1 h -1 ) are comparable to rates in natural systems (21,100-155,500 molecules PSII -1 h -1 ). Compared to other synthetic systems, we achieve 2 to 3 orders of magnitude higher ATP generation rates and single CO2-fixation reactions. For all calculations, 617 chlorophylls per PS II were assumed [START_REF] Danielsson | Quantification of photosystem I and II in different parts of the thylakoid membrane from spinach[END_REF], except for the system described by Lee et ** Reaction rate, not a carbon fixation rate. † TEM was added in excess. On a per Chl or PSII basis, we expect higher rates when thylakoids are limiting.

Molecules / PSII reaction center / hour

Figure 1 :

 1 Figure 1: Light-driven cofactor regeneration by thylakoid membrane-based energy modules (TEM) (A) NADPH production is dependent on light and externally added ferredoxin (B) ATP production is dependent on light, with some background reaction in the dark due to membrane bound adenylate kinase (Fig. S1B). (C) Scheme of TEM-driven carboxylation reactions of propionyl-CoA carboxylase (Pcc) and crotonyl-CoA carboxylase/reductase (Ccr) utilizing light-produced ATP and NADPH, respectively. (D) Reactions coupled to TEM (2.5 or 5 µg Chl and 60 µmol photons m -2 s -1 ) (N=6).

Figure 2 :Figure 3 :

 23 Figure 2: Light-driven, continuous fixation of CO2 into organic acids (A) Scheme of CETCH version 6.0 for the conversion of CO2 into glycolate coupled to TEM. (B-C)13 C-labeling patterns and total levels of methylmalonyl-CoA (blue) and ethylmalonyl-CoA (orange) over time, starting the CETCH cycle with 80 µM propionyl-CoA. (B) CETCH cycle version 6.0 directly operated by 125 µg Chl mL -1 TEM under constant illumination (60 µmol photons m -2 s -1 ). Shown is the extracted ion peak area and the fractional labeling of ethylmalonyl-CoA, as well as methylmalonyl-CoA (in shades of orange and blue, respectively, see Supplementary Fig.4for explanation of the labeling pattern) (C) same as in (b) but in the dark, showing that light is required to operate the cycle. Ethylmalonyl-CoA is not produced in the dark when starting from propionyl-CoA (n.d., not detected). (D) Glycolate production in the light and the dark by CETCH version 6.0.

Figure 4 :

 4 Figure 4: Light-driven, continuous fixation of CO2 into organic acids by CETCH version 7.0 coupled to TEM in micro-droplets. (A) Scheme of the CETCH version 7.0 coupled to TEM operating inside microdroplets. (B) Dynamic equilibrium states of NADPH fluorescence of four populations of droplets: Droplets containing TEM (60 µg Chl mL -1 ), 1 mM NADP + and CETCH version 7.0 (teal line), droplets containing TEM, 1 mM NADP + and an additional ATP regeneration system (Ppk and polyphosphate, coral line), as well as control droplets containing 1 mM NADPH and all CETCH version 7.0 components except for Ccr (black line), and control droplets containing TEM, 1 mM NADP + and all CETCH version 7.0 components except for Ccr (green line). (C) Images of the droplets from (B) using the same color coding; first row, left to the right: bright field, thylakoid fluorescence with overlap from the coding dye, coding dye; second row, left to the right: NADPH fluorescence before illumination, after 15 minutes, and after 30 minutes illumination (scale bar corresponds to 100 µM). A time-lapse video is available as movie S4. (D) Glycolate formed per acceptor molecule (sum of crotonyl-CoA and 3-hydroxybutyryl-CoA) over time in droplets and in bulk solution. The light and dark curves represent droplets maintained in the light and in the dark. The

  Crotonyl-CoA and propionyl-CoA were synthesized from their respective anhydrides according to D. Peter et al. (35). (S)-methylsuccinyl-CoA and mesaconyl-CoA were synthesized via the mixed anhydride method starting from the free acids and obtaining a racemic mixture of 2-(S)-methyl and 3-(S)-methyl-thioester. Ethylmalonyl-CoA and methylmalonyl-CoA were enzymatically produced with either crotonyl-CoA carboxylase or propionyl-CoA carboxylase starting from crotonyl-CoA or propionyl-CoA according to Schwander et al. and Peter et al.

FNR

  expression plasmid was provided by Dr. Winkler and described in Rumpel et al. (36). The Rhodobacter sphaeroides 2.4.1 electron transport flavoprotein-ubiquinone oxidoreductase was cloned from genomic DNA (using the forward 5'-TAT ACA TAT GAC CGA GCA GAC TCC C and reverse 5'-TAT AGG TCT CGG ATC CTC ACA TGT TGG GAT AGT TCG primers) into pET16b vector containing a Strep-tag using NdeI and BamHI. The PCR product was cut with BsaI and NdeI to avoid the naturally occurring internal BamHI sites. The Pseudomonas migulae electron transport flavoprotein-ubiquinone oxidoreductase was codon optimized and synthesized by BaseClear B.V. (Leiden, Netherlands).

  and stored at -20° or -80° C. Unless otherwise specified, His-tagged enzymes were purified by resuspending the cell pellet 1:2 (w/v) ratio in Buffer L (50 mM HEPES pH 8.0 or 20 mM Tris-HCl pH 8.1, 500 mM NaCl, 5 mM MgCl2, 10% glycerol, and DNAse) and lysed by ultrasonication. The lysate was clarified by ultracentrifugation (1 hour at 100,000 × g) and the resulting supernatant was filtered through a 0.45 or 0.2 µm filter. Lysate was loaded onto a HisTrap FF (GE Healthcare, Freiburg, Germany) and unspecifically bound protein was removed with a buffer containing: 50 mM HEPES-KOH pH 8.0 or 20 mM Tris-HCl pH 8.1, 500 mM NaCl, and 75 mM imidazole. The protein was eluted in 50 mM HEPES-KOH pH 8.0 or 20 mM Tris-HCl pH 8.1, 500 mM NaCl, and 500 mM imidazole. The eluted protein was either desalted in a buffer containing: 50 mM HEPES-KOH pH 8.0 or 20 mM Tris-HCl pH 8.1, and 150 mM NaCl with a HiTrap 5 ml Desalting (GE Healthcare, Freiburg, Germany) column or by gel filtration using a HiLoad 16/600 Superdex 200 pg (GE Healthcare, Freiburg, Germany) size exclusion column equilibrated with a buffer containing: 50 mM HEPES-KOH pH 8.0 or 20 mM Tris-HCl pH 8.1, and 200 mM NaCl. Elution fractions were concentrated with Amicon Ultra-4 centrifugal filters (Merck Millipore, Darmstadt, Germany). Purified proteins were stored in 30-50% Glycerol at -20°C or -80°C and the concentration was determined on a Nanodrop 2000 (Thermo Scientific, St. Leon-Rot, Germany) from extinction coefficients calculated on ProtParam, unless otherwise specified. Recombinant production and purification of 4-hydroxybutyryl-CoA dehydratase (Nmar0207), 4-hydroxybutyryl-CoA synthetase (Nmar0206), and 2-(S)-methylsuccinyl-CoA oxidase (Mco) was purified as described in Schwander et al

  dwell time, and fragmentor voltage set to 35 V, 20 ms, and 380 V respectively. The following MRM transitions were used to quantify the CoA esters : ethylmalonyl-CoA (882 m/z  428 m/z and 331 m/z), methylsuccinyl-CoA (882 m/z  428 m/z and 375 m/z), succinyl-CoA (868 m/z  428 m/z and 361 m/z), methylmalonyl-CoA (868 m/z  428 m/z and 317 m/z), propionyl-CoA (824 m/z  428 m/z and 317 m/z), crotonyl-CoA (836 m/z  428 m/z and 329 m/z), and β-/ γhydroxybutyryl-CoA (854 m/z  428 m/z and 347 m/z). To complement the MRM data, CoA esters were also UV detected at 260 nm on an Agilent 1290 Infinity II DAD detector equipped with a Max-Light cartridge cell (60 mm).

  13 L/min, 225 °C) and sheath gas (12 L/min, 400°C). The dwell time and fragmentor voltage were 50 ms and 380 V respectively. Optimized collision energy used for the analytes were as follows: ATP (506 m/z  408 m/z, 25 V, 506 m/z  159 m/z, 35 V); ADP (426 m/z  159 m/z, 25 V, 426 m/z  79 m/z, 35 V); and AMP (346 m/z  134 m/z, 35 V, 346 m/z  79 m/z, 25 V).

1 -

 1 bit emulsions containing CETCH v7.0 and TEM Droplets containing TEM powered CETCH v7.0 were generated from a solution (total volume, 1.8 mL) that contained 70 µg Chl/mL in a buffer that contained 50 mM HEPES-KOH, concentrations of sulforhodamine B, thylakoids, NADPH, and NADP + . Population 1 contained: 0 µg Chl mL -1 of thylakoids, 0.5 mM NADP + , 2 µM sulforhodamine B. Population 2 contained: 11 µg Chl mL -1 of thylakoids, 0.5 mM NADP + , 8 µM sulforhodamine B. Population 3 contained: 0 µg Chl mL -1 of thylakoids, 0.5 mM NADPH, 40 µM sulforhodamine B. Droplets were prepared and monitored as discussed above.

Ferredoxin, 52 U

 52 mL -1 superoxide dismutase, 1.2 µM catalase, 0.75 mM ADP, and various concentrations of sulforhodamine B, thylakoids, NADPH, and NADP + . Population 1 contained: 23 µg Chl mL -1 of thylakoids, 0.5 mM NADP + , 2 µM sulforhodamine B. Population 2 contained: 0 µg Chl mL -1 of thylakoids, 0.5 mM NADPH, 40 µM sulforhodamine B.

  Fig. S2. Oxygen evolution(A) Relative molar NADP + photoreduction and O2 evolution curves over light/dark cycles. The O2 production occurs in a 1:2 molar ratio with NADPH, the same ratio that occurs under physiological conditions. (B) NADPH production with O2 evolution curves at 60 µmol photons m -2 s -1 . Lines are the average of three replicates and the standard deviation is shown in the shaded area. (C) Product formation from Ccr and Pcc alongside the O2 evolution measurements. (D) Relative O2 evolution at 60 or 300 µmol photons m -2 s -1 in a reaction buffer either with or without catalase (Cat) and superoxide dismutase (SOD). (E) A similar experiment as in (D) but an even lower light condition is shown. All conditions contained SOD and catalase. At 30 µmol m -2 s -1 the O2 evolution was slower but was maintained longer.

  m -2 s -1 300 µmol photons m -2 s -1 no Cat or SOD 60 µmol photons m -2 s -1 60 µmol photons m -2 s -1 no Cat or SOD

Fig. S4 .Fig. S5. 3 - 1 Fig. S6 .

 S431S6 Fig. S4. Expected 13 CO2 isotopic labelling pattern in the CETCH cycleShown is the expected labelling pattern for the first two turns of the CETCH cycle starting at either crotonyl-CoA or propionyl-CoA using isotopic labelling with13 C-bicarbonate. The cycle features two CO2-incorporation steps per turn catalyzed by Ccr (shown in blue) and Pcc (shown in red).13 C-labeled carbon incorporated into the C4-acceptor crotonyl-CoA by Ccr remain with the output molecule glyoxylate when β-methylmalyl-CoA is split by Mcl into propionyl-CoA and glyoxylate (position and migration of the 13 C-label is shown in blue). The carbon incorporated into the C3-acceptor propionyl-CoA (shown in red) stays with the acceptor molecule during each turn of the cycle (position and migration of the13 C-label is indicated by different shades of red). Note that the CETCH cycle includes carbon skeleton-rearranging steps catalyzed by mutases, resulting in a complex labelling pattern.

Fig. S7 .

 S7 Fig. S7. Developing a functional Mcd reaction for CETCH v7.0. In natural systems, the conversion of methylsuccinyl-CoA to mesaconyl-CoA is catalyzed by Mcd. Mcd is a FAD-dependent acyl-CoA dehydrogenase, which is coupled via electron transfer flavoproteins (Etf) to the membrane-located ubiquinone pool. During the development of the CETCH cycle Mcd alone and in combination with its cognate Etf was not sufficient to operate the CETCH cycle (2). This required engineering of a Mco that was ultimately used in CETCH v5.4. Mco can impair TEM productivity through ROS and free FAD (fig. S5A) and therefore, we aimed to replace Mco in the CETCH cycle with a functional Mcd reaction. (A) Mcd (6.75 µM) from Rhodobacter sphaeroides (McdRs) alone does not catalyze the conversion of methylsuccinyl-CoA (starting with 250 µM, shown in black) into mesaconyl-CoA (grey). The decrease of methylsuccinyl-CoA in the reaction mixture is due to spontaneous CoAthioester hydrolysis. (B) Mcd in combination with 6.25 µM of its cognate Etf from R. sphaeroides (EtfRs) is able to form mesaconyl-CoA, likely due to re-oxidation of Etf in the presence of O2. (C) Addition of 6.25 µM Etf-ubiquinone oxidoreductase from Pseudomonas migulea (EtfQOPm) increases the conversion of methylsuccinyl-CoA into mesaconyl-CoA by McdRs and EtfRs more than tenfold. (D) Replacing Mco in CETCH v6.0 with McdRs, EtfRs, and EtfQOPm (3, 8, and 1 µM respectively) creates CETCH v7.0. Comparison of glycolate formed from CETCH v6.0 (Mco-based) and CETCH v7.0 (Mcd-Etf-EtfQObased) using Ppk and Fdh as regeneration systems and starting with 2 mM NADP + and 0.5 mM ADP.

Fig. S8 .

 S8 Fig. S8. Description of the microfluidic platform. (A) Microfluidic workflow. Thylakoids are encapsulated in 300 pL water-in-oil (w/o) droplets using a dropmaker device with two parallel production nozzles (30x30 µm). Two devices are used in parallel to produce 4-bit emulsions. Droplets are then flowed into an incubation chamber and stored as a 2D-array for light activation and time-lapse microscopy imaging. (B) Optical setup. The 2D-incubation chamber is integrated on the stage of an inverted microscope equipped with a 10x objective. A white-light LED and a 365 nm LED are used for the light activation of the thylakoids and the NADPH fluorescence excitation, respectively. The two LEDs are triggered together with the camera using a home-made LabVIEW routine to perform automated time-lapse fluorescence imaging with defined light/dark cycles. A 550 nm LED is used for the sulforhodamine B fluorescence excitation (barcoding). (C) Bright-field image of a 4-bit emulsion and droplet radius distribution. (D) 550 nm (barcoding) fluorescence image and droplet fluorescence distribution. (E) 365 nm (NADPH) fluorescence image. Linear relationship between NADPH concentration and 365 nm fluorescence. Scale bars are 100 µm unless specified.

Fig. S9 .

 S9 Fig. S9. Image processing workflow. (A) Typical sequence of processed images: bright-field, 550 nm LED and 365 nm LED time-lapse images (0, 17, 27 and 37 min). Scale bars are 100 µm. (B) Image processing of the sequence. A region of interest is defined. Droplet positions and radii are extracted from the bright-field image. The 4-bit droplet barcoding is extracted from the 550 nm fluorescence image. The NADPH level of each droplet over time is extracted from the 365 nm fluorescence time-lapse imaging. (C) Dynamics of NADPH concentration at the single droplet level are shown by 365 nm fluorescence versus time for each individual droplet. The mean for each population is indicated in bold. In a typical experiment, N = 50 for each population. For more clarity, only population 1 and population 4 are shown here. On the right, the average of the same populations is shown with the corresponding standard deviation indicated by the shaded area.

  mM sorbitol (dashed line), where the TEM activity collapses after three light/dark cycles. NADPH concentration of all populations was corrected for the non-catalytic oxidation observed in the NADPH-only control.

Fig. S15 .

 S15 Fig. S15. Coupled single carboxylase reaction to TEM controlled with an external signal. (A) Scheme of the TEM/Ccr-coupled system in microdroplets. Light triggers TEM-dependent production of NADPH, which is used by crotonyl-CoA carboxylase/reductase (Ccr) to catalyze the reductive carboxylation of crotonyl-CoA to ethylmalonyl-CoA. (B) NADPH concentration over time under light (50 µmol photons m -2 s -1 ) and dark cycles of TEM (120 µg Chl mL -1 ) coupled to Ccr (42 nM) in microdroplets. TEM in microdroplets is shown in green, Ccr coupled to TEM in microdroplets is shown in orange. Similar to the Ghr coupling experiment seen in fig. S14D, a stabilizing effect of increased sorbitol can be observed (solid lines represent droplets containing 700 mM sorbitol and dashed lines 330 mM). NADPH concentration of all populations was corrected for the non-catalytic oxidation observed in the NADPH-only control (0.8 mM NADPH).

Chl/hour) Calculated or measured rates (µmoles/mg Chl/hour)

	Ccr in droplets	6.4 †	--	--	--	This work (measured values, Ccr 1-bit experiment)
	Pcc and Ccr reaction in bulk	124	30.5 ‡	62**	61**	This work (Fig. 1D)
	CETCH in bulk	0.55 †	>2.2 ‡ ‡	--	--	This work (Fig. 2D)
	CETCH in Droplets	0.21 †	>0.84 ‡ ‡	--	--	This work (CETCH v7.0 in droplets)
	ATP & NADPH measurements bulk	--	71.5 ‡	65	143	This work (Fig. 1A, B, and fig. S1B)
	Measurement	Carbon fixation rate	O 2 evolution	ATP	NADPH Source
	Isolated chloroplasts	50	--	--	--	Kalberer, et al. 1967 (47)
	Isolated chloroplasts	130-280	--	--	--	Heber et al. 1978 (48)
	Isolated chloroplasts	40-60	--	--	--	Reeves and Hall 1973 (49)
	Isolated chloroplasts (Spinach)	38	--	--	--	Avron and Gibbs, 1974 (50)
	Natural
	Isolated chloroplasts	--	55	165*	110*	Heber, 1973 (51)
	Isolated chloroplasts	--	122	367*	245*	Heineke et al., 1989 (52)
	Isolated chloroplasts	--	231	693*	462*	Stitt, 1986 (53)
	Isolated thylakoid membranes (in vitro)	--	--	--	27 ± 3	Yacoby et al., 2011 (54)
	Synthetic Reconstituted photosynthetic system			0.9	--	Feng et al., 2015 (19)
	ATP & NADPH measurements bulk	--	71.5 ‡	65	143	This work (Fig. 1A, B, and fig. S1B)
	This work
	TEM in droplets	--	11.8 ‡	--	23.5	This work (Fig 3C)

  al. that was calculated using 35 chromophores per PS II[START_REF] Lee | Photosynthetic artificial organelles sustain and control ATP-dependent reactions in a protocellular system[END_REF].

		Measurement	Carbon fixation rate	ATP	O2 evolution	Source
		Isolated chloroplasts	27,800	--		Kalberer, et al. 1967 (47)
	Natural	Isolated chloroplasts	72,200-155,500	--		Heber et. al. 1978 (48)
		Isolated chloroplasts	22,200-33,300	--		Reeves and Hall, 1973 (49)
		Isolated chloroplasts (Spinach)	21,100	--		Avron and Gibbs 1974 (50)
	Synthetic or Hybrid	CO2 Fixation-single reaction ATP production ATP Production	34*	29* 500		Lee et al., 2018 (18) Lee et al., 2018 (18) Feng et al., 2015 (19)
		O2 evolution			9000	Sokol et al., 2018 (5)
		ATP production		36000		This work (Fig. 1B)
		Ccr in droplets	3600 †			This work (measured values, Ccr 1-bit experiment)
	This work	Ghr in droplets	21300 † **			This work (measured values, Ghr 1-bit experiment)
		O2 evolution			26600	This work (fig. S2E, calculated from first 2 minutes)
		Pcc and Ccr reaction in bulk	68600			This work (Fig. 2D, CETCH v6.0 in bulk)
		CETCH in bulk	303 †			This work (CETCH v7.0 in droplets)
		CETCH in Droplets	119 †			This work (measured values)
	* Calculated using 35 chromophore per PSII (18)

Table S9 .

 S9 DNA sequence of the codon optimized genes used in this work

	Gene name	Codon optimized DNA sequence
	FdxCr	TACAAGGTCACCCTGAAAACCCCTAGCGGCGATAAAACGATTGAGTGCCCAGCCGACACTTACATTTTG
		GATGCTGCTGAAGAGGCGGGGCTGGACCTGCCGTATTCGTGTCGCGCGGGTGCCTGCTCTTCATGCGCG
	(petF) from C.	GGCAAAGTGGCCGCAGGCACCGTGGATCAAAGCGACCAGTCATTCTTAGACGATGCGCAGATGGGTAA
	reinhardtii	CGGTTTTGTGCTGACGTGTGTAGCTTATCCGACGAGTGATTGCACTATCCAAACACATCAGGAAGAAGC
		GCTGTATTAA
	FdxSp1	GCAGCATATAAAGTGACGCTGGTGACTCCGACCGGTAACGTAGAATTTCAGTGTCCTGATGACGTCTAT
		ATCCTTGATGCTGCTGAAGAGGAAGGCATCGATTTACCATACTCCTGTCGCGCCGGTTCGTGCTCAAGCT
	(Fdx1) from S.	GCGCCGGTAAACTGAAGACGGGATCATTGAACCAAGACGATCAGAGCTTCCTGGACGACGACCAGATT
	oleracea	GATGAAGGGTGGGTTCTGACATGCGCGGCGTACCCGGTGAGCGATGTTACCATTGAGACCCATAAGGAA
		GAAGAACTCACCGCGTAA
	FdxSp2	GCGACTTACAAAGTCACCTTAGTTACACCATCTGGTTCACAAGTTATTGAATGTGGTGACGATGAATATA
		TCTTGGACGCCGCGGAAGAGAAAGGTATGGATCTGCCGTACTCCTGTCGCGCGGGCGCATGCTCGTCGT
	(petF) from S.	GCGCAGGTAAAGTAACTTCAGGCTCGGTGGACCAGAGCGATCAGAGCTTTTTGGAAGATGGACAGATG
	oleracea	GAAGAAGGCTGGGTGCTCACATGCATAGCCTATCCGACCGGCGATGTGACGATCGAAACCCATAAGGA
		GGAAGAGTTGACCGCCTAA
		ATGGCTAGCTGGAGTCATCCGCAATTTGAGAAAATCGAAGGTCGCCAGATTGCATCTGATGTGGAAGCC
		CCACCACCCGCTCCGGCGAAAGTGGAGAAACATAGCAAAAAAATGGAAGAAGGCATCACAGTTAATAA
		ATTTAAACCAAAAACACCTTATGTTGGACGATGCTTGTTGAATACCAAGATCACCGGCGATGACGCCCC
		TGGTGAGACTTGGCACATGGTCTTCTCCCACGAAGGCGAGATCCCTTACCGTGAGGGCCAATCGGTTGG
		GGTCATTCCGGATGGCGAAGATAAAAATGGTAAACCGCACAAACTGAGGCTGTACTCAATAGCCAGTA
	FNRSp	GCGCATTAGGGGATTTCGGGGATGCAAAGTCCGTCTCACTGTGCGTTAAACGCCTGATTTATACTAATGA CGCTGGTGAAACCATCAAAGGCGTATGCTCGAATTTTTTATGTGATCTGAAACCGGGCGCAGAGGTAAA
	(FNR) from S. oleracea	GTTAACGGGCCCGGTGGGTAAAGAAATGCTGATGCCGAAGGACCCCAACGCAACCATTATTATGCTCGG TACTGGGACGGGCATTGCTCCGTTTCGTTCTTTTCTTTGGAAAATGTTTTTTGAGAAACACGATGATTATA AATTCAACGGTCTCGCCTGGCTATTCCTCGGTGTCCCGACGTCCTCATCGCTGCTGTACAAGGAAGAGTT
		CGAGAAAATGAAGGAAAAAGCTCCGGACAACTTCCGCCTTGATTTCGCGGTGAGCCGTGAGCAGACCA
		ACGAAAAAGGCGAAAAAATGTATATCCAGACCCGGATGGCGCAGTACGCGGTGGAACTGTGGGAAATG
		TTGAAAAAGGACAACACCTATTTTTATATGTGTGGTCTGAAAGGGATGGAGAAGGGCATTGATGACATT
		ATGGTGAGTCTTGCCGCGGCGGAAGGAATTGACTGGATCGAATACAAGCGCCAGCTGAAAAAAGCGGA
		ACAGTGGAACGTGGAAGTGTATTGA
		ATGGAGCGTGAGTACATGGAATTTGATGTCGTAATTGTTGGGGCTGGTCCTGCTGGTCTTTCTGCGGCGT
		GTCGCTTAAAGCAAAAAGCCGCAGAGGCTGGGAAAGAAATCAGCGTATGTGTTGTTGAAAAGGGGAGT
		GAGGTGGGTGCTCATATCTTATCTGGTGCTGTTTTTGAGCCACGCGCCCTGAATGAGCTGTTCCCTGACT
		GGAAGGAACTGGGAGCCCCTCTTAACACTCCTGTAACTCGCGATGATATCTTTGTGTTGAAAAATGCGG
		ATTCAGCACAAAAAATTCCAGACCTTTTTGTTCCAAAGACCATGCACAACGAGGGCAACTACATTATCT
		CCCTGGGAAATCTGTGTCGTTGGTTGGCCCAACAAGCAGAAAACTTAGGTGTAGAGATCTACCCGGGAT
		TTGCTGCGCAGGAGGCTCTGTTTGATGAAAATGGAGTAGTCCGTGGTATCATTACTGGGGATTTAGGTGT
		AGACCGTGAGGGACATCCCAAGGAGGGATTGTATACACCGGGTATGGAGTTACGTGGCAAGTATACGTT
		GTTCGCAGAAGGCTGCCGCGGTCATATTGGAAAACAATTGATTAAACGCTTCAACCTTGACTCGGAAGC
		TGATGCCCAACACTATGGTATTGGACTTAAAGAAATCTGGGAGATCGATCCAGCCAAACATCAGCCCGG
		GCTGGTCGTGCACACGGCGGGCTGGCCTTTAGACATCATGGGAACTGAGAACACAGGGGGTTCGTTTTT
	ETF:QOpm	ATATCATCTTGAGAACAACCAGGTTGTCGTCGGTTTGATCGTTGACCTTTCATACTCCAACACGTATCTG
	(Etf:QO) from	TCCCCCTTTGATGAGTTTCAGCGTTTGAAGCATCACCCTGTTCTGAAGCAGTATCTGGAGGGTGGTAAAC
	P. migulea	GTATCTCGTATGGTGCACGCGCGATCTGCAAAGGCGGCCTGAACTCGCTGCCTAAAATGGTATTCAAGG
		GTGGTGCCCTTATCGGCTGCGATCTTGGAACTTTAAATTTCGCGAAGATCAAAGGATCACACACCGCCAT
		GAAGAGCGGGATGTTGGCGGCAGAAAGCGTGGCTGAGGCGCTTTTTGCGGAGAAGGATGGAACTGAGG
		AATTGACCACGTATGTCGATGCGTTTAAAAAATCGTGGCTTTATGACGAGTTGTTCGCCTCGCGTAATTT
		TGGGCCGGCTATTCACAAGTTCGGGGCCATTGTCGGTGGGGGCTTTAACTGGCTTGACCAGAATATCTTC
		GGAGGAAAACTTCCCTTCACGTTACACGACACTAAGCCCGACTACGCCTGCTTGAAACTTGCAGCGGAT
		TGTAAGAAAATCGATTATCCAAAGCCCGACGGTAAAATCTCTTTTGACAAACTGTCTAGCGTCTTTATTT
		CGGGTACGAATCACGAGGAAGAACAGCCTTGTCATCTGAAATTGACCGATCCCTCCATCCCCATCGCAA
		AAAATTTACCCATGTACGACGAACCTGCCCAGCGCTACTGTCCCGCGGGGGTTTACGAAGTCGTGACGA
		AGGAGGACGGGGAGAAACGTTTCCAAATCAATGCCCAGAACTGTGTTCATTGCAAAACGTGCGACATTA
		AGGATCCTGCTCAGAACATCACGTGGGTAGCGCCTGAAGGTGCTGGTGGCCCAACATACCCAAATATGT
		AA

Acknowledgements

We thank J. Zarzycki, D. Strand, and S. Burgener for enlightening discussions, and G. Stoffel for providing CoA esters. Funding: This work was supported by the Max Planck Society (MaxSynBio), the European Research Council grant (ERC 637675 'SYBORG'), as well as the US Department of Energy Joint Genome Institute, a DOE Office of Science User Facility (contract no. DE-AC02-05CH11231) with T.J.E. as grantee. J.-C.B. acknowledges the financial support by the 'Région Aquitaine' and by the French Government 'Investments for the Future' Programme, University of Bordeaux Initiative of Excellence (IDEX Bordeaux; (ANR)-10-IDEX-03-02). T.E.M. and R.M. were supported by the International Max-Planck Research School for Environmental, Cellular and Molecular Microbiology, Marburg, Germany. Author contributions: T.E.M., T.B., T.S., J.-C.B and T.J.E. conceived the project. Characterization and optimization of thylakoid preparations was done by T.E.M. Couplings of the CETCH cycle to thylakoids in bulk were performed by T.E.M. together with T.S. and C.D. The ETF:QO system as electron acceptor for Etf was developed by T.E.M and R.M. Mass spectrometric analyses were performed by N.C.S. and P.C. and the data was analyzed by T.E.M. The microfluidic platform to encapsulate thylakoids was developed by T.B. and J.-C.B. T.B. and T.E.M. planned, performed and analyzed microfluidic experiments with assistance from T.C. The software for light/dark cycles time lapse fluorescence microscopy, as well as the image processing software to analyze TEM activity in droplets was developed by M.G. Experimental data was analyzed by T.E.M., T.B., and T.J.E. The manuscript was written by T.E.M., T.B., J.-C.B. and T.J.E. with contributions from all other authors. Competing interests: J.-C.B. is a founder and scientific advisor at Emulseo. The authors declare no other competing interests. Data and materials availability: All data is available in the main text or supplemental material. The LabVIEW code used for image analysis has been deposited to GitHub (34).

Supplementary Material

Materials and Methods Supplementary Movies 1-4 Supplementary Figures 123456789101112131415161718Supplementary Tables 123456789References 34-64

Supplementary Materials for

Light-powered CO2 fixation in a chloroplast mimic with natural and synthetic parts Tarryn E. Miller, Thomas Beneyton, Thomas Schwander, Christoph Diehl, Mathias Girault, Richard McLean, Tanguy Chotel, Peter Claus, Niña Socorro Cortina, Jean-Christophe Baret*, Tobias J. Erb* *Corresponding author. Email: toerb@mpi-marburg.mpg.de (T.J.E.), jean-christophe.baret@ubordeaux.fr (J.-C.B.)

This PDF file includes:

Materials and Methods

Captions for Movies S1 to S4

Figs. S1 to S18

Tables S1 to S9

References Other Supplementary Materials for this manuscript include the following:

Movies S1 to S4 pH 7.8, 700 mM Sorbitol, 10 mM sodium L-ascorbate, 90 µM crotonyl-CoA, 0.5 mM ADP, 2 mM NADP + , 5 mM MgCl2, 5 mM K2HPO4, 10 mM KCl, 50 mM NaH 13 CO3, 10 mM polyphosphate, 1.2 µM catalase, 310 nM superoxide dismutase, 5 µM FdxCr, 1.3 µM GhrA, 14 µM PhaJ, and the core enzymes from CETCH v7.0 (listed in Supplemental Table 3). Ecm and Mcm were incubated with 2 µl of a buffered solution of 5 mM coenzyme B12 for 30 minutes in the dark and at room temperature prior to adding the enzymes to the reaction mixture. The samples (30 µL) were taken and quenched as described above. The CoA esters were measured using an Agilent 6550 iFunnel Q-TOF LC-MS and quantified using the integrated UV260nm peak and a standard curve. The glycolate produced was derivatized and measured by UPLC-MS/MS (using Agilent 6495B Triple Quad LC/MS) as described above.

Thylakoid activity in droplets 2, 3, & 4-bit emulsions

Thylakoid Stability

Thylakoid stability was assayed (fig. S11B). Four populations of droplets were created from 0.4 mL solutions that contained 50 mM HEPES-KOH, pH 7.

Controlling TEM in droplets with fluctuating light conditions

The effect of fluctuating light conditions in the droplets was tested (fig. S13). Three populations of droplets were created from 0.5 mL solutions that contained: 50 mM HEPES-KOH, pH 7.8, 330 mM sorbitol, 5 mM K2HPO4, 10 mM KCl, 5 mM MgCl2, 10 mM sodium L-ascorbate, 5 µM Ferredoxin, 52 U mL -1 superoxide dismutase, 1.2 µM catalase, 0.8 mM ADP, and various

The 2 populations of droplets were filled into the observation chamber via two inlets. After 2 minutes in the dark, the droplets were exposed to 50 µmol photons m -2 s -1 light. The light was turned off again after 60 minutes.

CETCH in droplets

Four-bit reaction conditions for droplets containing CETCH v6.0 and 7.0 that were monitored in the 2D array chamber described in Table S7

Movie S1.

Time-lapse of NADP + photoreduction in droplets containing various concentrations of TEM (experiment shown in Fig. 3B). Images show NADPH fluorescence, excited using a 365 nm diode, images taken every 2.5 minutes.

Movie S2.

Time-lapse of NADPH oscillations in light/dark cycles of droplets containing the Ghr reaction (experiment shown in Fig. 3F). Images show NADPH fluorescence, excited using a 365 nm diode, images taken every 2.5 minutes.

Movie S3.

Time-lapse of NADPH fluorescence of experiment demonstrating how the metabolic activity of droplets can be controlled in time and space (experiment shown in Fig. 3G). Images show NADPH fluorescence, excited using a 365 nm diode. After 2 minutes in the dark, the droplets were exposed to 50 µmol photons m -2 s -1 light. The light was turned off again after 60 minutes. The images were taken every minute for the first 5 minutes, at 7.5 minutes, then every 5 minutes until 125 minutes, and taken every 10 minutes after that.

Movie S4.

Time-lapse of the NADPH fluorescence of droplets encapsulated with variations of the full CETCH cycle (experiment shown in Fig. 4B &C, detailed droplet contents can be found in Table S7). Images show NADPH fluorescence, excited using a 365 nm diode. The images are taken every 2.5 minutes. During encapsulation, the reaction mixture incubates for about one hour in the dark and at room temperature. To assess the effect of prolonged incubations of the reaction mixture before illumination, we measured glycolate production rates of CETCH v7.0 coupled to TEM in bulk with simulated conditions during encapsulation. (A) Glycolate formed starting from 120 µM propionyl-CoA when reactions are illuminated directly after mixing (teal line) or kept in dark conditions (grey line). (B) Glycolate formed when starting from both propionyl-CoA (blue) and crotonyl-CoA (purple) (120 and 90 µM, respectively) after one hour incubation in the dark. Samples were taken at 0, 5, 15, 30, 60, 90, and 120 minutes after illumination (60 µmol photons m -2 s -1 ) or at 0, 60, and 120 minutes after the initial 1-hour incubation for samples that remained in the dark. These results from a representative experiment suggest that, with prolonged incubation times, starting from crotonyl-CoA leads to higher production rates compared to starting from propionyl-CoA. This might be explained by adenylate kinase activity producing ATP in the dark (see fig. S1C), which allows propionyl-CoA carboxylase (Pcc) to carboxylate propionyl-CoA to methylmalonyl-CoA, which is subsequently converted into succinyl-CoA. Succinyl-CoA is prone to spontaneous hydrolysis, likely lowering overall productivity of the system. As a result, we used crotonyl-CoA, and not propionyl-CoA as described by Schwander et al. [START_REF] Schwander | A synthetic pathway for the fixation of carbon dioxide in vitro[END_REF], to prepare CETCH-and TEMcontaining microdroplets, mimicking the chloroplast. A B The enzyme highlighted in blue is Mco that was used in CETCH v6.0, and those highlighted in orange are those used in CETCH v7.0. The last two enzymes, highlighted in green, are used in the cycle but are not part of the core reactions.

Table S4.

Detailed pipetting schemes of multiplexed Ghr coupling experiments. Some internal components were varied (either enzyme concentration or substrate concentration). In each experiment, four populations were multiplexed and analyzed simultaneously. Grey boxes indicate the component was omitted, and concentrations of components that were varied are indicated.

Protein concentration

Substrate concentration

Droplet population