Effect of wheat straw pretreated with liquid fraction of digestate from different substrates on anaerobic digestion performance and microbial community characteristics.

The effects of liquid fraction of digestate (LFD) pretreatment on anaerobic digestion (AD) performance and microbial community characteristics were estimated. Prior to AD, LFD (LFD, LFD, and LFD) collected separately from three continuously stirred tank reactors (CSTRs) using swine manure (SM), food waste (FW), and wheat straw (WS) as the mono-substrate was applied to pretreat WS. The results showed that AD with LFD pretreatment resulted in biomethane yields of 240.2-277.9 mL·gVS, a 33.57%-54.54% improvement over the yield of the control, and also produced a time saving of 32.26%-46.77%. The pretreatment parameters were optimized for LFD pretreatment. The enhancement effect was in the order of LFD > LFD > LFD. Simultaneously, the cellulose, hemicellulose and lignin contents in the WS and their characteristics (surface properties, crystallinity index, etc.) varied accordingly. The function of the microbial community was strengthened during the pretreatment stage, but the structure of the microbial community had a clear response to the LFD source substrates. Bacteroidetes was the most dominant phyla and was positively correlated with the hydrolysis rate. Consequently, the LFD from the different substrates used as pretreat agents could improve the AD performance of WS.