Metagenome reveals the possible mechanism that microbial strains promote methanogenesis during anaerobic digestion of food waste.

For better understanding the mechanism of microbial strains promoting methane production, four strains Hungatella xylanolytica A5, Bacillus licheniformis B1, Paraclostridium benzoelyticum C2 and Advenella faeciporci E1 were inoculated into anaerobic digestion systems. After bioaugmentation, the cumulative methane production of A5, B1, C2 and E1 groups elevated by 11.68%, 8.20%, 18.21% and 15.67% compared to CK group, respectively. The metagenomic analysis revealed that the species diversity and uniformity of the experimental groups was improved, and hydrolytic acidifying bacteria, represented by Clostridiaceae, Anaerolineaceae and Oscillospiraceae, and methanogens, such as Methanotrichaceae and Methanobacteriaceae, were enriched. Meanwhile, the abundance of key genes in carbohydrate, pyruvate and methane metabolism was increased in the inoculated groups, providing reasonable reasons for more methane production. The strengthening mechanism of microbial strains in this study offered a theoretical foundation for selecting a suitable bioaugmentation strategy to solve the problems of slow start-up and low methane production in anaerobic digestion.