Hydrogen production from propionate at various concentrations by Rhodopseudomonas capsulata, a purple nonsulfur bacterium, was studied at a temperature of 31 degrees C, a pH of 7.0, and an illumination intensity of 3000 Lux. Among the six levels of propionate, 3.84 g/L was found to be the optimum propionate concentration for H2 production in terms of substrate utilization efficiency, H2 percentage, cumulative H2 production, and H2 yield. A modified Gompertz equation was able to describe properly the production of H2 from propionate. A comparative study of H2 production with acetate, propionate, and butyrate at 40 mM showed that, as a substrate for H2 production by R. capsulata, propionate was better than butyrate, but less favorable than acetate.
Copryright 2004 Humana Press Inc.