Effect and mechanism analysis of dual enzyme pretreatment on enhancement of volatile fatty acids production in kitchen waste anaerobic acidification

Abstract

The high content of cellulose and hemicellulose in kitchen waste (KW) results in a slow hydrolysis rate and subsequently hinders the yields of volatile fatty acids (VFAs) in anaerobic acidification. In this study, cellulase and hemicellulase were used for the pretreatments of KW to tackle the problem of difficult hydrolysis in anaerobic acidification. The results indicated that the joint use of double enzymes significantly improved the hydrolysis of cellulose and hemicellulose during pretreatment, thus enhancing the VFAs production in anaerobic acidification. The highest production of TVFAs was 50.73 ± 2.10 g COD/L and it was improved by 62.77% compared with the unpretreated group. In addition, the 16S rRNA amplicon sequencing analysis showed that the relative abundance of Firmicutes related with the VFAs production increased from 17.77% to 50.55%. The potential metabolism function analysis (PICRUSt2) indicated that the enrichment of glyceraldehyde-3-phosphate dehydrogenase (EC:1.2.1.9) and acetyl-CoA C-acetyltransferase (EC:2.3.1.9) contributed to the production of VFAs in AD. The results suggested that collaborative enzyme pretreatment could be one of the effective methods for the hydrolysis of cellulose and hemicellulose in KW and provided constructive mechanistic insights into recovering valuable products from KW.