Photoproduction of hydrogen from raw starch using a halophilic bacterial community

The bacterial community designated BC1, which originates from night soil treatment sludge, exhibited a strong ability to produce H2 from raw starch in the light in the presence of 3% NaC1. Three halophilic or halotolerant bacterial species, Vibrio fluvialis, Rhodobium marinum, and Proteus vulgaris, were isolated from BC1 and identified. The level of H2 production from starch by coculture of V. fluvialis and R. marinum was nearly equal to that by BC1, indicating that these two strains play roles in starch degradation and H2 production from the degraded products in BC1, respectively. Acetic acid and ethanol, which were detected as the major products of degradation of starch by V. fluvialis in pure culture, seemed to be mainly utilized for H2 production by R. marinum in BC1 and the coculture. However, R. marinum in pure culture could not produce H2 from a synthetic medium containing acetic acid and ethanol, suggesting that V. fluvialis supplied not only substrates but also some unknown factors capable of inducing H2 production from these substrates by R. marinum. A study using the starch-rich microalgae, Chlamydomonas reinhardtii and Dunaliella tertiolecta, demonstrated that the above coculture could be applied to the production of H2 at high yield from raw starch in an algal biomass.