Abstract
Photobiological $H_2$ production was compared using purple non-sulfur bacteria Rhodobacter sphaeroides KD131 in the medium containing various organic acids as the carbon source and electron doner under illumination of $110\;W/m^2$ using halogen lamp at $30^{\circ}C$. The organic acids used were 0~120 mM acetate, butyrate, lactate and malate. Initial pH 7.0 and cell concentration 1.0 at 660nm were increased to pH 8 and 4.4~5.1, respectively during 24hrs of photo-fermentation when lactate and malate were used. However, acetate and butyrate increased pH to 9 and cell concentration to 3.2~3.9 of malate at the same experimental conditions. Optimum ranges of organic acids concentration and carbon/nitrogen ratio were 30~60 mM and 10~20, respectively. When malate was used as the substrate, maximum $H_2$ production 1.1 ml $H_2$/ml broth, which is equivalent to 1.97 mol $H_2$/mol malate was observed.
