Diverse acetate-oxidizing syntrophs contributing to biogas production from food waste in full-scale anaerobic digesters in China

Anaerobic digestion is a sustainable biotechnology for treating food waste (FW) with biogas production driven by microorganisms. Generation of FW increased greatly in China, which are mainly treated with anaerobic digestion technology. A survey into nine full-scale mesophilic anaerobic FW digesters was conducted, together with four sewage sludge digesters as a comparison, to investigate the specific physicochemical features and the resulted microbiota. Results showed that FW digesters were characterized with high salt, volatile fatty acid and ammonia concentrations. A unique “core” microbial community indigenous inside FW digesters was identified, including 70 bacterial and 4 archaeal genus-level taxa, which was quite different from that in sludge digesters. Stable carbon isotope signature of biogas revealed that, hydrogenotrophic methanogenesis (HM) played a significant role in methane generation. The hydrogenotrophic Methanobacterium demonstrated strong positive correlations with the syntrophic acetate oxidizing bacteria (SAOB) Syntrophaceticus and other SAOB candidates (Aminobacterium, Gelria, DTU014, Alkaliphilus), forming a unique SAO-HM functional guild which particularly prevailed in digesters receiving household FW. Feedstock composition was the essential factor influencing microbial structure, followed by salinity, ammonia, and VFAs. The high ammonia concentration and prominent contribution of diverse SAO-HM players indicate that, tailored management strategy needs to be developed for treating household FW.