Single-stage photo-fermentative hydrogen production from hydrolyzed straw biomass using Rhodobacter sphaeroides

The hydrogen production utilizing photosynthetic and anaerobic bacteria in two-stage approach has many drawbacks, such as shortage of raw materials and complexity of operations. Accordingly, we aimed to develop a simple one-stage H2 production protocol using the depolymerization of maize straw cellulose as a cheap carbon source. R. sphaeroides HY01 and its mutant (Hup−) were studied regarding their H2 production under different culture conditions. Further study using two model sugars, their combination, and straw hydrolysate as carbon sources was conducted to determine the effects of substrate on H2 production. When using the straw hydrolysate as carbon source, the pH remained in a range of 7.1-7.6, whereas it dropped to 5.4-7.4 when using the model sugars, and the former biomass value was greater. The H2 production performance of the mutant was significantly better than that of HY01. One-step photo-fermentative H2 production was superior when using straw hydrolysate as opposed to the simple model sugars, and its yield was up to 4.62 mol H2·mol−1 reducing sugar.