Engineering Microbial Consortium Biohybrid System to Efficiently Produce Electricity from Lignocellulose Biomass.

Abstract

Converting lignocellulose into bioelectricity through a bioelectrocatalytic system (BES) has emerged as a promising approach to addressing environmental pollution and energy regeneration challenges. However, practical application of BES is significantly constrained by the fact that the electroactive biocatalyst Shewanella oneidensis lacks the essential metabolic pathways and enzymes required for utilizing lignocellulose for cell growth and power generation. Here, to realize clean electricity production from lignocellulose hydrolysate, an artificial microbial consortium comprising S. oneidensis, Lactococcus lactis, and Bacillus subtilis was developed. In this consortium, L. lactis is responsible for converting glucose into lactate; B. subtilis metabolizes glucose and xylose into riboflavin; and S. oneidensis then employs lactate as an electron donor and riboflavin as an electron shuttle to facilitate electricity generation. Subsequently, to increase substrate conversion efficiency of the microbial consortium, three key genes codY, ribA, and dld encoding lactate dehydrogenase, GTP cyclohydrolase, and d-lactate dehydrogenase, were expressed in L. lactis, B. subtilis, and S. oneidensis, respectively, which accelerated glucose-to-lactate conversion, riboflavin synthesis, and lactate metabolism. Also, to accelerate the extracellular electron transfer (EET) capacity of the microbial consortium, the cyc2 gene from Acidithiobacillus ferrooxidans encoding the outer membrane c-type cytochrome was further expressed in S. oneidensis. Finally, to further enhance the interfacial EET capability of the microbial consortium, a 3D microbiota biohybrid system S₇L₁B₁@CF&GO consisting of carbon felts and graphene oxide was developed to reduce the internal resistance of BES. The results showed that the artificial biohybrid system could obtain a maximum power density of ∼739.40 mW m^-2 using lignocellulosic hydrolysate as the carbon source. This system expands the range of carbon sources available to S. oneidensis for efficient power generation from the lignocellulosic hydrolysate.