Biohydrogen Production by Dark Fermentation of Starch Using Mixed Bacterial Cultures of Bacillus sp and Brevumdimonas sp.

The energy use of hydrogen is recognized for its environmental advantages. Its utilization is expected to grow significantly over the coming years, and the development of new production methods to complement or substitute the traditional steam reforming, gasification, or electrolysis will further enhance that growth. The microbial conversion of biomass is considered to be the route with the highest immediate potential for its significant hydrogen yield and low energy requirement. The present research investigates this potential, using starch as the raw material for dark fermentation and by using appropriate micro-organisms. Fermentation using a single micro-organism strain is shown to be of limited efficiency for H2 production, with a low H2 content and low yield. The combination of two bacterial strains, belonging to Bacillus sp and Brevumdimonas sp., respectively, and each with a specific action in the H2 production, significantly enhances the biohydrogen production yield. Its H2 yield reached 1.04 mol H2/mol glucose, being twice the yield obtained with pure cultures. The specific hydrogen production rate was up to 400 mL H2/(g biomass h). The end products were mainly butyric and acetic acid, with traces of ethanol. The dark fermentation of starch can be considered to be a butyrate-type fermentation.