Insight Into The Fate Of Antibiotic Resistance Genes In Co-composting Green Tea Processing Plant Residues With Farm Wastes

With the rapid development of China's tea processing industry in recent years,a large amount of tea residues have produced,which retains rich nutritious components and biologically active ingredients.At the same time,tea residues are also a well-adsorbed substance with a porous structure.At present,the utilization rate of tea residues is very low,resulting in huge waste of resources and environmental pollution.Antibiotics and heavy metals are widely used as feed additives to adapt to the intensive and large-scale rapid development of the livestock and poultry industry.However,most antibiotics and heavy metals are not completely absorbed by animals and are excreted in urine and feces in the form of their original or metabolite,and antibiotic resistance genes(ARGs)and metal resistance genes(MRGs)may be produced due to selective pressure.At the same time,heavy metals in animal feces will also exert selective pressure on ARGs,thereby promoting the further spread of ARGs.In the environment,resistance genes can be spread or even enriched in the environment by horizontal gene transfer(HGT)through mobile gene elements(MGEs),which weakens the efficacy of antibiotics and seriously threatens human life and health.Aerobic composting is one of the main ways of harmless solid waste and resource utilization,and it is also a commonly used technology to reduce ARGs in solid waste.In view of the unreasonable utilization of tea residues and the resistance gene residues in livestock and poultry manure,this paper uses green tea processing plant residues and farm wastes to compost,and the chemical properties,active metal content,abundance of ARGs,MRGs,MGEs and microbial communities in the co-composting process of green tea processing plant residues and farm wastes were studied,and the correlations among ARGs,MGEs,MRGs,microbial communities and environmental factors were analyzed in order to provide a theoretical basis and effective referencefor the changes in ARGs during the co-composting process of green tea processing plant residues and swine manure.The main results and conclusions obtained are as follows:(1)The temperature of the two treatment piles was maintained above 55°C for 3d and 4d respectively,both of which met the requirements of harmless composting and standard hygiene.The addition of green tea processing plant residues extended the high temperature period of compost,accelerated the compost maturation process,reduced nitrogen loss and significantly reduced the concentrations of bio-Cu and bio-Zn.(2)The addition of green tea processing plant residues significantly reduced the abundance of ARGs(80.5%),MGEs(89.65%)and MRGs(95.95%)after composting,especially the abundance of tet and sul antibiotic resistance genes and int I1.Adding green tea processing plant residues during the composting process can reduce the spread of resistance genes by reducing the abundance of MGEs and inhibiting HGT,thereby reducing the potential risks associated with composting products.(3)Firmicutes,Proteobacteria,Actinobacteria and Bacteroidetes are the main bacterial phylum in the composting process.The addition of green tea residues reduced the abundance of potential human pathogens such as Turicibacter,Pseudomonas.RDA analysis showed that green tea residues can reduce the abundance of MRGs and ARGs by reducing the bioavailability of heavy metals.Network analysis showed that the potential host bacteria of ARGs mainly belong to Firmicutes and Actinobacteria,and ARGs,MGEs and MRGs have the same potential host bacteria,green tea processing plant residues can reduce the abundance of ARGs by reducing the abundance of potential host bacteria.In summary,co-composting with green tea processing plant residues and swine manure can prolong the high-temperature period of composting,promote compost maturation,and reduce the contents of bioavailable heavy metals in compost products.Moveover,the addition of green tea processing plant residues effectively improves the reduction effect of ARGs,MGEs and MRGs in the composting system,and also effectively reduces the abundance of human pathogenic bacteria in the composting products,and increases the safety of the composting products.The conclusion of this study provides a theoretical basis for the application of green tea residue in composting.