Metabolically versatile Rhodobacter sphaeroides as a robust biocatalyst for H₂ production from lignocellulose-derived mix substrates

Biological hydrogen production has received much attention and it is of practical interest to produce H₂ biologically using low-cost lignocellulose-derived mix substrates, usually containing various compounds, such as arabinose, formate, acetate, furfural, HMF, in addition to glucose and xylose. Herein, we systematically evaluated impacts of single/mixed model compounds, and energy sorghum hydrolysate on H₂ production by Rhodobacter sphaeroides. We found (i) obvious cell growth was observed for all single substrates including formate, furfural and HMF, which for the first time, were reported in R. sphaeroides; (ii) cultures pairing acetate with a mixture of glucose and xylose remarkably improved H₂ production compared to that without acetate; (iii) arabinose/formate had limited effects on the mixed-sugar photo-fermentation; (iv) furfural/HMF degradation was expedited by co-utilization with glucose and xylose. The results support the conclusion that photo-fermentation with hydrolysate achieved comparable, or even advantageous H₂ production over that of model compound mixtures. Metabolic diversity in R. sphaeroides enables the well-performed degradation of complex substrates for biofuel production.