Effect of the inoculum mixing ratio on the anaerobic digestion of food waste: Reactor performance and microbial community

Anaerobic digestion (AD) of food waste (FW) needs to break the hydrolysis limit and improve efficiency. Mixed inoculants of different sources are often used to enhance AD performance, while the mechanism of interaction between mixed inoculants of different sources is uncertain. The effect of the mixing ratio of two different inoculants, Baijiu pit mud (PM) and anaerobic digested sludge (ADS), on the AD of FW was examined. Specifically, the five ratios of PM:ADS (1:0, 3:1, 1:1, 1:3, and 0:1, based on volatile solids) on the AD performance and microbial community were evaluated. Biogas production was 551.70 % higher under a PM:ADS ratio of 1:3 (408.62 mL/g VS) compared with a ratio of 0:1. The acidification rate in 1:3 was 84.05 % and it was 41.85 % higher than 0:1(42.2 %). The abundance of unclassified_f_Comamonadaceae (degradation of cellulose), Petrimonas (acid and hydrogen production) and Methanobrevibacter were higher following the PM addition. Furthermore, the abundance of key enzymes (F420 hydrogenase) and methane metabolism (ko00680) varied under different ratios of PM:ADS. These results suggest that the addition of PM promotes the acidification and methanogenic phases of the AD of FW.