Property-specific Biopolymer Production in Electroactive Biofilms

Although the biology- and yield-improving potentials of a few industrially relevant electroactive biofilms have been investigated to a minimal extent, an efficient bioprocess system control for biofilm-based bioproduction is yet to be reported. However, the controlled application of electrical potential could be employed to modulate biofilm metabolism (respiration) in a manner that favors the secretion of the target EPS component. In this study, various regimes of electrochemical techniques are employed to produce polyglutamic acid (PGA) with specific molecular weights and stereoisomeric properties over a period of 48 h. In the first stage, biofilm formation and electroactivity are enhanced via specific stressors, followed by varied potentiostat-controlled biocatalyst respiration and its influence on specific product formation in the matrix. Lastly, the key molecular genes encoding the proteins facilitating the electroactive bioprocess in tandem with specific properties of PGA will be characterized for further process improvement. The biofilm produced by Bacillus subtilis PB5760 was enhanced in the presence of 17 mM choline chloride-based deep eutectic solvent from 0.23 to 1.44 as measured using a crystal violet assay. Also, the molecular weights of the polyglutamic acid (PGA) content of the matrix obtained under an applied potential of 0.4 V and open circuit potentiometry (OCP) were 2.168 x 10⁶ and 3.986 x 10⁶ Daltons, respectively. Under the stated experimental conditions, polydispersity indexes (Mz/Mn) of 1.957 and 2.310 were obtained at 0.4 V and OCP, respectively, which are key factors that determine the usefulness of PGA in the food, cosmetic, pharmaceutical, and biomedical sectors. This platform potentially offers a non-invasive, real-time monitoring and control system of microbial redox states by channeling electron flux without having to produce undesired by-products in the form of reduced organic compounds during fermentation.