Simultaneous regulation of biocathodic γ-HCH dechlorination and CH4 production by tailoring the structure and function of biofilms based on quorum sensing

Abstract

Dechlorination of chlorinated organic pollutants and methanogenesis are attractive biocathode reductions in microbial electrolysis cells (MECs). Quorum sensing (QS) is applied to regulate microbial communications. However, how acyl-homoserine lactones (AHLs)-dependent QS organize the assembly of the biocathode microbial community, and then regulate multiple biocathode reductions remains unclear. By applying N-butanoyl homoserine lactone (C4-HSL), N-hexanoyl homoserine lactone (C6-HSL) and 3-oxo-hexanoyl homoserine lactone (3OC6-HSL) in γ-hexachlorocyclohexane (γ-HCH) contaminated MECs, this study investigated the changes of biofilm microbial structure and function and the mechanisms of AHLs-QS on γ-HCH dechlorination and CH4 production. Exogenous C4-HSL and 3OC6-HSL increased cytochrome c production and enriched dechlorinators, electroactive bacteria but not methanogens to accelerate γ-HCH dechlorination and inhibit CH4 production. C6-HSL facilitated dechlorination and CH4 production by enhancing biofilm electroactivity and increasing membrane transportation. Besides, exogenous C6-HSL restored the electron transfer capacity that was damaged by the concurrent addition of acylase, an endogenous AHL quencher. From the perspective of microbial assembly, this study sheds insights into and provides an efficient strategy to selectively accelerate dechlorination and CH4 production by harnessing microbial structure based on QS systems to meet various environmental demands.