Synergy of multi-enzyme pretreatment and Paraclostridium benzoelyticum bioaugmentation: A dual strategy for enhancing methane production in dry anaerobic digestion of kitchen waste

Dry anaerobic digestion (DAD) of kitchen waste (KW) has low methane production due to the poor mass transfer and the low abundance of functional microorganisms. This study employed multi-enzyme pretreatment (PRE), bioaugmentation with Paraclostridium benzoelyticum (BIO), and their combination (COM) to enhance methane production. Interestingly, the COM group had the highest methane production, which was increased by 18.51 %, 9.91 % and 12.39 % compared with the control, PRE and BIO groups, respectively, which indicated that there was a synergy between multi-enzyme pretreatment and bioaugmentation. Further analysis of microbial community and metagenome was conducted to reveal the synergistic mechanism. The results showed that in COM group, the enrichment of the Rikenellaceae, Methanobacteriaceae and Methanosaetaceae was the directly reason for enhancing methane production. Additionally, key metabolic functions including biosynthesis of cofactors, methane metabolism and oxidative phosphorylation also played a pivotal role in boosting methane production. Furthermore, the enhancement of the hydrogenotrophic methanogenesis pathway has been demonstrated to be a critical factor in the synergistic effects. It provided a reliable theoretical basis for the practical application of the multi-enzyme pretreatment combined with Paraclostridium benzoelyticum bioaugmentation for DAD.