Abstract
The development of hydrogen fermentation from organic waste has drawn much attention because it contributes the formation of the recycling society. It was often observed, however, that hydrogen fermentation from organic waste was suddenly terminated, and one of the possible reasons is the inhibitory effect of lactic acid bacteria. Therefore, this paper focused on the effect of lactic acid bacteria, which is Lactobacillus paracasei isolated from the waste in the bean curd manufacturing, on hydrogen fermentation with respect to theinfluence of pH. The coculture of Lb. paracasei inhibited the hydrogen fermentation by Cl. acetobutylicum. This inhibition was more significant under pH 4.5 than pH 6.5. It was found that the supernatant of the culture medium of Lb. paracasei also inhibited the hydrogen fermentation and that this inhibition was visible under less than pH 5 and disappeared under more than pH 6.2. And the results of the agar well diffusion test where chymotrypsin and trypsin were applied as proteases clarified that Lb. paracasei excreted a bacteriocin and that it stopped the growth of hydrogen producing bacteria. The molecular weight of the bacteriocin in the supernatant of the culture medium of Lb. paracasei seemed to be between 1, 350 and 17, 000.
