Electrochemical control of metabolic flux of Weissella kimchii AM: Neutral red immobilized in cytoplasmic membrane as electron channel

Abstract

Electrochemical control of the metabolic flux of W kimchii ski 0 on glucose and pyruvate was studied. The growing cell of W. kimchii sk 10 produced 87.4 mM lactate, 69.3 mM ethanol, and 4.9 mM lactate from 83.1 mM glucose under oxidation condition of the anode compartment, but 98.9 mM lactate, 84.3 mM ethanol, and 0.2 mM acetate were produced from 90.8 mM glucose under reduction condition of the cathode compartment for 24 h, respectively. The resting cell of W. kimchii sk10 produced 15.9 mM lactate and 15.2 mM acetate from 32.1 mM pyruvate under oxidation condition of the anode compartment, and 71.3 mM lactate and 3.8 mM acetate from 79.8 mM pyruvate under reduction condition of the cathode compartment. The redox balance (NADH/NAD(+)) of metabolites electrochemically produced from pyruvate was 1.05 and 18.76 under oxidation and reduction conditions, respectively. On the basis of these results, we suggest that the neutral red (NR) immobilized in bacterial membrane can function as an electron channel for the electron transfer between electrode and cytoplasm without dissipation of membrane potential, and that the bacterial fermentation of W kimchii sk 10 can be shifted to oxidized or reduced pathways by the electrochemical oxidation or reduction, respectively.