| With the development of agriculture and livestock farming,a large amount of animal manure and lignocellulosic waste is generated.Improper handling of these wastes and animal manure can cause serious environmental pollution and waste of resources.Composting is an appropriate method that effectively transforms organic solid waste through microbial and enzymatic actions.It not only efficiently degrades lignocellulose but also removes certain antibiotic resistance genes from animal manure.The humus produced after composting can be used for soil remediation and improvement of soil fertility.However,traditional composting processes have disadvantages such as slow fermentation rate and low degradation rate of lignocellulose,which seriously affect the efficiency of composting.Ionic liquids(ILs)have been proven to be a reliable treatment method for lignocellulose,as they can disrupt the crystallinity of lignocellulose and promote its degradation.Moreover,ILs not only influence the microbial community involved in lignocellulose degradation but also affect the hosts of antibiotic resistance genes.However,further research is needed to determine whether ILs can improve composting conditions,promote lignocellulose degradation and humification,and eliminate antibiotic resistance genes.This study investigates the composting of a mixture of sawdust and cow dung and explored the effects of ILs on the physicochemical parameters,organic matter degradation,changes in dissolved organic matter,degradation of lignocellulose,carbohydrate functional enzymes,humification process,microbial communities,and antibiotic resistance genes during the composting process.The research demonstrated that ILs regulated the physicochemical parameters of composting,enhanced organic matter degradation,promoted the transformation of dissolved organic matter,accelerated lignocellulose degradation and humification process.Metagenomic analysis revealed that ILs increased the abundance of Actinobacteria and Proteobacteria in the composting.Compared to the untreated control group,the total abundance of carbohydrate functional enzymes GH11,GH6,AA6,and AA3＿2 in the ILstreated group increased by 13.98%,10.12%,11.21%,and 13.68% respectively.Additionally,ILs up-regulated the gene abundance of carbohydrate metabolism and amino acid metabolism,increased the contribution of Actinobacteria and Proteobacteria,and promoted composting humification.The study also investigated the regulatory mechanism of antibiotic resistance genes(ARGs)during ILs composting.The results indicated that macrolide-lincosamidestreptogramin(MLS)resistance genes,chloramphenicol resistance genes,tetracycline resistance genes,and β-lactam resistance genes decrease gradually during composting.From day 0 to day 3,the MLS resistance genes in the control group(CK)and ILs-treated group(T)decreased by 25.62% and 26.66%respectively;the tetracycline resistance genes decreased by 7.21% and 7.86%respectively;the chloramphenicol resistance genes decreased by 2.85% and3.34% respectively;and the β-lactam resistance genes decreased by 1.95% and3.69% respectively.Mechanistic studies revealed that ILs can inhibit the growth of some antibiotic resistance gene hosts,particularly Firmicutes,leading to a reduction in antibiotic resistance genes.Additionally,the down-regulation of certain key genes may contribute to the effective reduction of ARGs abundance.In conclusion,the research results confirmed that ILs can optimize the microenvironment of compost to promote the degradation of lignocellulose,enhanced humification,and improved the removal of antibiotic resistance genes,providing a new approach and new insight for improving the quality of compost,and a new strategy for the treatment of organic solid waste and the recycling of livestock and poultry manure. |
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