Lignocellulosic depolymerization induced by ionic liquids regulating composting habitats based on metagenomics analysis.

The application of ionic liquids with sawdust and fresh dairy manure was studied in composting. The degradation of organic matter (OM), dissolved organic matter (DOM), and lignocellulose was analyzed. The DOM decreased by 14.25 mg/g and 11.11 mg/g in experimental group (ILs) and control group (CK), respectively. OM decreased by 7.32% (CK) and 8.91% (ILs), respectively. The degradation rates of hemicellulose, lignin, and cellulose in ILs (56.62%, 42.01%, and 23.97%) were higher than in CK (38.39%, 39.82%, and 16.04%). Microbial community and carbohydrate-active enzymes (CAZymes) were analyzed based on metagenomics. Metagenomic analysis results showed that ionic liquids enriched Actinobacteria and Proteobacteria in composting. Compared with CK, the total abundance values of GH11, GH6, AA6, and AA3_2 in ILs increased by 13.98%, 10.12%, 11.21%, and 13.68%, respectively. Ionic liquids can improve the lignocellulosic degradation by regulating the environmental physicochemical parameters (temperature, pH, C/N) to promote the growth of Actinobacteria and Proteobacteria and carbohydrate-active enzymes (CAZymes) abundance. Therefore, ionic liquids are a promising additive in lignocellulosic waste composting.