Exopolysaccharides matrix affects the process of extracellular electron transfer in electroactive biofilm

The applications of bioelectrochemical systems (BESs) in the field of environment and energy are achieved through the bioelectrocatalytic process of electroactive biofilms. As a primary component of biofilm, the role of exopolysaccharides in electroactive biofilm in BESs is poorly understood. This study constructed an exopolysaccharides-deficient Geobacter sulfurreducens-based BES to explore the role of exopolysaccharides in electroactive biofilm. Compared with the wild type, the mutant biofilm expressing less exopolysaccharides de-creased the capacity of current generation. In the mutant biofilm, the content of exopolysaccharides decreased significantly, resulting in a thinner biofilm and lower cell viability compared with the wild-type biofilm. How-ever, the mutant with overexpressed pili developed a mature biofilm with extended time, which indicating the importance of exopolysaccharides for early biofilm formation and the compensatory role of pili in biofilm for-mation. The mutant biofilm had less content of c-type cytochromes (c-Cyts) and lower electrochemical activity of extracellular polymeric substances than the wild-type biofilm, suggesting a function of exopolysaccharides an-choring extracellular c-Cyts that essential to extracellular electron transfer (EET) in electroactive biofilms. Our findings demonstrated the essential role of exopolysaccharides in the process of EET in electroactive biofilm, which contributed to a better understanding and optimization of the performance of BESs. (c) 2021 Elsevier B.V. All rights reserved.

Automated summary

The study investigated the role of exopolysaccharides in electroactive biofilms by constructing an exopolysaccharides-deficient Geobacter sulfurreducens-based BES. The findings demonstrated the essential role of exopolysaccharides in extracellular electron transfer (EET) and early biofilm formation, with pili playing a compensatory role in biofilm formation. The mutant biofilm had lower cell viability, thinner biofilm, and decreased electrochemical activity compared to the wild-type biofilm.