Biohydrogenation From Biomass Sugar Mediated by in Vitro Synthetic Enzymatic Pathways

Biohydrogenation catalyzed by enzymes is becoming more accepted, especially for synthesis of chiral compounds. The pairs of substrate/enzyme for NAD(P)H generation include alcohol/alcohol dehydrogenase, formate/formate dehydrogenase, glucose/glucose dehydrogenase, glucose-6-phosphate (G6P) /G6P dehydrogenase, dihydrogen/hydrogenase, and phosphite/phosphite dehydrogenase. Here we demonstrate high-yield generation of NAD(P)H from a renewable biomass sugar – cellobiose through an in vitro synthetic enzymatic pathway (SyPaB) consisting of 12 purified enzymes and coenzymes. The NADPH yield was as high as 11.4 mol NADPH per cellobiose (i.e., 95% of theoretical yield – 12 NADPH per glucose unit) in a batch reaction. Consolidation of endothermic reactions and exothermic reactions in one pot results in the biohydrogenation reaction between xylose and cellobiose with an amazingly high energy-retaining efficiency of 99.6%. The high-yield and low-cost production of polyols from the fermentation-toxic biomass hydrolysate by SyPaB might be important to produce hydrocarbons by aqueous phase reforming.