Magnetite-boosted syntrophic conversion of acetate to methane during thermophilic anaerobic digestion

Abstract

Using a batch thermophilic anaerobic system established with 60 mL serum bottles, the mechanism on how microbial enrichments obtained from magnetite-amended paddy soil via repeated batch cultivation affected methane production from acetate was investigated. Magnetite-amended enrichments (MAEs) can improve the methane production rate rather than the methane yield. Compared with magnetite-unamended enrichments, the methane production rate in MAE was improved by 50%, concomitant with the pronounced electrochemical response, high electron transfer capacity, and fast acetate degradation. The promoting effects might be ascribed to direct interspecies electron transfer facilitated by magnetite, where magnetite might function as electron conduits to link the acetate oxidizers (Anaerolineaceae and Peptococcaceae) with methanogens (Methanosarcinaceae). The findings demonstrated the potential application of MAE for boosting methanogenic performance during thermophilic anaerobic digestion. HIGHLIGHTS Magnetite boosted the syntrophic conversion of acetate to methane during thermophilic anaerobic digestion.; Magnetite-amended enrichments exhibited pronounced electrochemical response and electron transfer capacity.; Magnetite might act as electron conduits to link acetate oxidizers and methanogens.; Magnetite might facilitate the establishment of direct interspecies electron transfer.; The addition of magnetite altered the bacterial community composition.;

Keywords

• acetate
• interspecies electron transfer
• magnetite
• methane
• microbial community structure
• thermophilic anaerobic digestion