Improvement of ethanol production by electrochemical redox coupling of Zymomonas mobilis and Saccharomyces cerevisiae.

Zymomonas mobilis was immobilized in a modified graphite felt cathode with neutral red (NR-graphite cathode) and Saccharomyces cerevisiae was cultivated on a platinum plate anode to electrochemically activate ethanol fermentation. Electrochemical redox reaction was induced by 3 approximately 4 volt of electric potential charged to a cathode and an anode. Z. mobilis produced 1.3 approximately 1.5 M of ethanol in the cathode compartment and S. cerevisiae did 1.7 approximately 1.9 M in the anode compartment for 96 hr. The ethanol production by Z. mobilis immobilized in the NR-graphite cathode and S. cerevisiae cultivated on the platinum plate was 1.5 approximately 1.6 times higher than those cultivated in the conventional condition. The electrochemical oxidation potential greatly inhibited ethanol fermentation of Z. mobilis but did not S. cerevisiae. Total soluble protein pattern of Z. mobilis cultivated in the electrochemical oxidation condition was getting simplified in proportion to potential intensity based on SDS-PAGE pattern; however the SDS-PAGE pattern of protein extracted from S. cerevisiae cultivated in both oxidation and reduction condition was not changed. When Z. mobilis culture incubated in the cathode compartment for 24 hr was transferred to S. cerevisiae culture in the anode compartment, 0.8 approximately 0.9 M of ethanol was additionally produced by S. cerevisiae for another 24 hr. Conclusively, total 2.0 approximately 2.1 M of ethanol was produced by the electrochemical redox coupling of Z. mobilis and S. cerevisiae for 48 hr.