초록
<P>Bioelectrochemical systems can affect microbial metabolism by controlling the redox potential. We constructed bioelectrochemical cultures of the proteolytic bacterium, <I>Coprothermobacter proteolyticus</I> strain CT-1, both as a single-culture and as a co-culture with the hydrogenotrophic methanogen, <I>Methanothermobacter thermautotrophicus</I> strain ∆H, to investigate the influences of bioelectrochemical regulation on facultatively syntrophic proteolysis. The co-culture and single-culture were cultivated at 55°C with an anaerobic medium containing casein as the carbon source. The working electrode potential of the bioelectrochemical system was controlled at −0.8V (vs. Ag/AgCl) for bioelectrochemical cultures and was not controlled for non-bioelectrochemical cultures. The cell densities of hydrogenotrophic methanogen and methane production in the bioelectrochemical co-culture were 3.6 and 1.5 times higher than those in the non-bioelectrochemical co-culture after 7days of cultivation, respectively. Contrastingly, the cell density of <I>Coprothermobacter</I> sp. in the bioelectrochemical co-culture was only 1.3 times higher than that in the non-bioelectrochemical co-culture. The protein decomposition rates were nearly proportional to the cell density of <I>Coprothermobacter</I> sp. in the all types of cultures. These results indicate that bioelectrochemical regulation, particularly, affected the carbon fixation of the hydrogenotrophic methanogen and that facultatively syntrophic proteolysis was accelerated as a result of hydrogen consumption by the methanogens growing well in bioelectrochemical co-cultures.</P>