Organic matter composition, BaP biodegradation and microbial communities at sites near and far from the bioanode in a soil microbial fuel cell

Abstract

Bioanodes in a soil microbial fuel cell (SMFC) can serve as sustainable electron acceptors in microbial metabolism processes; thus, SMFCs are considered a promising in situ bioremediation technology. Most related studies have focused on the removal efficiency of contaminants. Relatively few efforts have been made to comprehensively investigate the organic matter composition and biodegradation metabolites of organic contaminants and microbial communities at various distances from the bioanode. In this study, the level and composition of dissolved organic matter (DOM), biodegradation metabolites of benzo[a]pyrene (BaP), and microbial communities at two sites with different distances (S1cm and S11cm) to the bioanode were investigated in an SMFC. The consumption efficiency of dissolved organic carbon (RDOC) and removal efficiency of BaP (RBaP) at S1cm were slightly higher than those at S11cm after 100 days (RDOC 47.82 ± 5.77% at S1cm and 44.98 ± 10.76% at S11cm; RBaP 72.52 ± 1.88% at S1cm and 68.50 ± 4.34% at S11cm). More fulvic acid-like components and more low-molecular-weight metabolites (indicating a higher biodegradation degree) of BaP were generated at S1cm than at S11cm. The microbial community structures were similar at the two sites. Electroactive bacteria (EAB) and some polycyclic aromatic hydrocarbon degraders were both enriched at the bioanode. Energy metabolism at the bioanode could be upregulated to generate more adenosine triphosphate (ATP). In conclusion, the bioanode could modulate the metabolic pathways in the adjacent soil by strengthening the contact between the EAB and BaP degraders, and providing more ATP to the BaP degraders.