Microbial response characteristics of integrated constructed wetland-microbial fuel cell systems to linear alkyl-benzene sulfonates.

Linear alkylbenzene sulfonates (LAS) are the most prevalent anionic surfactants utilized in detergents and cleaning products. This study took sodium dodecyl benzene sulfonate (SDBS) as target LAS, and preliminarily explored the effects of LAS on the microbiological characteristics of constructed wetland-microbial fuel cell (CW-MFC) systems. Results showed that, SDBS had no impact on the physical processes such as adsorption and sedimentation in CW-MFC but significantly affected the subsequent biodegradation process. SDBS stimulated the biosynthesis of extracellular polymeric substances within CW-MFC, with proteins showing a greater resistance to LAS toxicity than polysaccharides. SDBS enhanced the enzymatic activity of microorganisms in CW-MFC due to its amphiphilic nature and solubilization capabilities. However, beyond a critical concentration, SDBS can become toxic, leading to a decrease or even complete loss of microbial enzymatic activity. SDBS also increased microbial community diversity and the proliferation of SDBS-degrading bacteria on lava and MFC anodes, but this promoting effect diminished as SDBS concentrations rose. SDBS promoted the growth of electrochemically active bacteria (EAB) on MFC anodes more at low concentrations than at high ones. Certain genera, such as Pseudomonas, Desulfovibrio, and Geobacter, exhibited higher tolerance to SDBS compared to other EAB. The CW-MFC system harbored seven bacterial genera capable of degrading SDBS, including Geobacter, which could degrade alkyl chains through β/ω-oxidations, Aeromonas, Acinetobacter, Desulfovibrio and Hydrogenophaga, which could perform desulfonation, Zoogloea and Dechloromonas, which could perform benzene ring cleavage. Geobacter and Desulfovibrio played dual roles as both EAB and SDBS-degraders in CW-MFC.