Ecological factors affecting H₂ production capacity of ethanol-type fermentation

The ethanol-type fermentation for bio-production of H₂ using both pure and mixed batch culture was studied, in which some ecological factors, including interspecies cooperation, glucose concentration, temperature and pH, affecting the H₂ production capacity and specific rate were investigated in order to maximize the H₂ output. The four strains, Bacteroides, Fusobacterium, Aerobacter, and Zymomonas, of higher hydrogen production capacity bacteria were isolated from the anaerobic activated sludge producing hydrogen, and were demonstrated to be ethanol-type fermentation bacteria. It was demonstrated that the complex micro-ecosystems such as anaerobic activated sludge were good for increasing the hydrogen production capacity. It was found that while Bacteroides of ethanol-type fermentation bacteria achieved the H₂ production capacity of 43.1 mmol H₂/g SS and the maximum specific H₂ production rate of 2.87 mmol H₂/g SS·hr, the anaerobic activated sludge could achieve those of up to 51.2 mmol H₂/g SS and 3.58 mmol H₂/g SS·hr, respectively, in its optimum conditions of glucose concentration =170.8 mM, temperature =36°C and pH=5.0. The optimum parameters were glucose concentration of around 200 mM, temperature of 36°C and pH of 5.0.