Electrofermentation increases concentration of poly γ‐glutamic acid in Bacillus subtilis biofilms

Abstract

Abstract Fluctuations in redox conditions in bioprocesses can alter the end‐products, reduce their concentration, and lengthen the process time. Electrofermentation enables rapid metabolic modulation of biosynthesis and allows control of redox imbalances in biofilm‐based fermentation processes. In this study, electrofermentation is used to boost the production of the bacterial biopolymer poly‐γ‐glutamic acid (γ‐PGA) from Bacillus subtilis ATCC 6051. When compared to control experiments (3.3 ± 0.99 g L−1), the application of an electrode potential E = 0.4 V versus Ag/AgCl results in a more than two‐fold increase in the production of γ‐PGA (9.13 ± 1.4 g L−1). Using an engineered B. subtilis strain, in which γ‐PGA production is driven by isopropyl β‐d‐1‐thiogalactopyranoside, electrofermentation improves polymer concentrations from 15.4 ± 1.5 to 23.1 ± 1.6 versus g L−1. These results confirm that electrofermentation conditions can be adopted to increase the concentration of γ‐PGA and perhaps other extracellular biopolymers in industrial strains.