Monday, July 25, 2011
Grand Ballroom, 5th fl (Sheraton New Orleans)
Butyrate-producing bacteria, Clostridium tyrobutyricum was cultivated in a cathode compartment with 0.1 mM neutral red at an applied potential of -400 mV vs. Ag/AgCl. Butyrate was mainly produced when sucrose was used as a carbon source. The final concentration (6.8±0.3 g/L), productivity (0.34±0.06 g/L/h), and yield (0.45±0.02 g/g sucrose) of butyrate was increased in the bioelectrical reactor (BER) compared to that in the batch reactor (5.2±0.4 g/L, 0.17±0.01 g/L/h, 0.35±0.01 g/g sucrose, respectively). Reduced neutral red at cathode was re-oxidized by NAD+ reduction inside cells. Thus, increased NADH was consumed for more butyrate production (2 NADH consumed for 1 butyrate production). MetaFluxNet, a modeling program for metabolic flux analysis, was used to evaluate metabolic flux distribution and to study the fractional flux response to an electron flow from cathode. Interestingly, formic acid was produced when pyruvate was used as carbon source in BER while not in the batch reactor. We found using bioinformatics tool that redox-sensitive transcriptional regulator is present at up-streaming of pyruvate-foramte lyase gene. The presence of activated protein in C. tyrobutyricum was checked by 2D-polyacrylamide gel electrophoresis. This is the first study to show the control of redox potential induced the change of microbial metabolism.