Analysis Of The Succession Of Functional Microbial Communities Degrading Lignocellulose And Prediction Of Functional Genes Via Metagenomics During Composting

The purpose of this study was to explore the succession of lignocellulosic degradation functional microorganisms and the expression of functional genes via metagenomics analysis during different agricultural waste composting processes.Since sugarcane pulp and cassava dreg were two kinds of agricultural wastes with different organic components and apparent structures,which made the degradation rate of lignocellulose and other organic components was different significantly during composting.The aerobic fermentation of bagasse pith-pig manure composting group(BP)and manioc waste-pig manure composting group(MW)lasted for 45 days.Firstly,the differences and variation trends of physicochemical properties in each composting matrix were detected and analyzed,and the content changes of lignocellulose(cellulose,hemicellulose and lignin)and dissolved organic matter(DOM)determine,as well.Then,metagenomic sequencing was used to conduct microbial ecological analysis of the composting samples to study the dynamic succession of lignocellulosic functional degradation bacteria community,gene expression encoding active carbohydrate enzymes and elimination efficiency of antibiotics and antibiotic resistance genes.Functional microorganism was combined with the expression of functional genes to study the degradation mechanism of lignocellulose during composting.The results showed that the degradation rate of organic matter in BP group and MW group was 29.14% and 15.59% respectively at the end of composting process.The degradation rate of cellulose,hemicellulose and lignin was 17.53 %,45.36 % and 36.48 %,respectively,higher than that of cassava slag-pig manure,which was 16.74 %,41.23 % and 29.77 %.What's more,there was less nitrogen loss in BP,indicating that sugarcane pulp was more suitable to be used as a bulking agent in composting.In addition,the diversity and abundance of lignocellulose-degrading microorganisms in BP were higher,and Proteobacteria,Actinobacteria,Firmicutes and Bacteroidetes were the dominant dominant bacteria degrading lignocellulose.During the thermophilic and cooling stages of composting,the relative abundance of genes encoding active carbohydrate active enzyme in the former was significantly higher than that in the latter,thereinto the Glycoside Hydrolases(GHs),Glycosyl Transferases(GTs)and Carbohydrate Esterases(CEs)were particularly obvious.In addition,compared with MW,the removal efficiency of antibiotics and antibiotic resistance genes in BP was higher.In conclusion,this study provides a new perspective to explore the synergistic degradation of lignocellulose by active carbohydrate enzymes at the genetic level,which is conducive to further excavate the molecular biological information during composting.