Demonstration of hydrogenase electrode operation in a bioreactor

This work describes the first step towards combination of the bioreactor with a starch-degrading microbial consortium and hydrogenase electrode (HE) in one unit for electricity generation. For this purpose, the bioreactor for microbial fermentation was designed with a set of electrodes (pH-sensor, Ag|AgCl reference electrode, Pt-electrode, and HE) inside the bioreactor. Potentials of all electrodes and H2 accumulation were monitored in the system under the precise pH control. Results obtained with the hydrogen-producing microbial consortium indicated that HE generates the potential equal to the H2|2H+ equilibrium potential. Furthermore, HE was able to catalyze the current generation (200 μA) by consuming H2 gas produced in the microbial consortium from starch. After 220 h of operation, HE retained at least 81% of the initial activity. Calculations of carbon balance indicated that fermentation products were similar in microbial cells without HE and with HE generating the current due to H2 consumption.