Microbial Mechanisms Of Multichannel Bioresource Efficient Utilization Of Food Waste And Their Control Of Antibiotic Resistance Genes

Food waste(FW)is rich in organic matter and can be reused through resource treatment.However,due to its complex sources and components,specific bioresource strategies need be adapted.Anaerobic digestion,aerobic composting and Hermetia illucens bioconversion are the main technologies for bioresource utilization of FW.Nevertheless,there are some problems such as low efficiency of anaerobic digestion,long composting cycle of aerobic composting,insufficient maturation of Hermetia illucens feces as well as FW leachate pollution that need to be solved urgently.In addition,the widespread presence of antibiotic resistance genes(ARGs)in FW poses a challenge for the control of ARGs in bioresource utilization.Microorganisms are the main body of organic matter bioconversion and ARGs transmission,and it is necessary to understand the microbial mechanisms of FW bioresource efficient utilization processes and their ARGs control in depth.Based on above issues,multichannel bioresource processes of different types of FW were studied in this thesis using fluorescence quantitative PCR and microbial high-throughput sequencing technique,the microbial mechanisms of biogas residue biochar(BC)and Fe Cl3 modified BC(Fe Cl3-BC)promoting the efficiency of anaerobic digestion and ARGs reduction were analyzed,the microbial mechanisms for improving aerobic composting efficiency and ARGs reduction by biodrying and mature compost inoculation(B&M)were revealed,the microbial mechanisms of efficient organic matter conversion and ARGs transmission in Hermetia illucens feces composting were clarified,and for FW leachate pollution,the variation of ARGs and microbial communities in biotreatment processes were explored.The main research results are as follows.1.Microbial mechanisms of BC and Fe Cl3-BC promoting anaerobic digestion efficiency and ARGs reduction.The addition of BC and Fe Cl3-BC increased cumulative methane production by 12.79% and 22.50%,respectively,by means of efficient organic matter metabolic activities such as glycolysis,fatty acids and pyruvate degradation as well as accelerated transformation of volatile fatty acids.Metagenomic analysis showed that BC,especially Fe Cl3-BC addition promoted the enrichment of Syntrophomonas and methanogenic archaea such as Methanofollis,Methanoculleus and Methanosarcina,which further enhanced the metabolic activities of methanol,dimethylamine and methylamine pathways,thereby causing more metabolically diverse methanogenesis.In addition,they promoted the relative abundances of functional genes pil A and fix A involved in direct interspecies electron transfer.The results of ARGs analysis indicated that BC,especially Fe Cl3-BC inhibited the replication and transmission of ARGs and their bacterial hosts by increasing reactive oxygen species.2.Microbial mechanisms of B&M improving aerobic composting efficiency and ARGs reduction.B&M could rapidly increase the abundance of Bacillaceae(66.59~94.44%)and the composting temperature(45.86~65.86℃),thus achieving the final maturity of FW composting in a short time by regulating microbial carbohydrate(14.02~15.31%)and amino acid metabolism(10.33~12.47%).Network analysis showed that high temperature could effectively inhibit the proliferation and spread of potential bacterial hosts of ARGs and integrons including Lactobacillaceae,Enterobacteriaceae,Leuconostocaceae and Corynebacteriaceae during initial composting.As a result,B&M significantly reduced the absolute(72.09~99.47%)and relative abundances(0.31~2.44 logs)of nearly all ARGs especially erm B,tet M,bla CTXM and bla OXA.3.Microbial mechanisms of efficient organic matter conversion and ARGs transmission in Hermetia illucens feces composting.Although the organic matter and moisture content were reduced after FW bioconversion by Hermetia illucens,the maturity standard was not reached,and the accumulation of salt was an important factor affecting seed germination.Microbial community analysis showed that uncultured Bacillaceae,Pseudogracilibacillus,Virgibacillus and Corynebacterium 1 from the gut of Hermetia illucens became the main bacteria in feces instead of Lactobacillus from FW.Correlation analysis showed that Corynebacterium 1,Escherichia-Shigella and Enterococcus of feces were potential hosts of ARGs.Physicochemical analysis indicated that both raw and semi-maturated pig manure promoted Hermetia illucens feces composting,and semi-maturated pig manure was more effective.Microbial community and their metabolic function analysis showed that the co-composting process improved the metabolic activities of major organic matter and humification by introducing functional microorganisms such as Bacillus,inhibited the denitrification process and enhanced the nitrogen fixation process.Network analysis showed the abundances of ARGs and their bacterial hosts increased obviously after the introduction of pig manure.Key functional microorganisms of composting process such as unclassified Micrococcales,uncultured Sphingobacteriaceae and unclassified Bogoriellaceae were also potential hosts of ARGs,which may affect the compost quality and increase the environmental risks of subsequent utilization of resource products.4.The variation of ARGs and microbial communities in leachate biotreatment processes.High ARGs abundances(absolute: 1.03×107~2.82×109 copies/m L,relative:0.076~2.778 copies/16 S r RNA)were observed across all samples.Although biotreatment effectively reduced the absolute abundance of ARGs,relative abundance of ARGs increased,which further increased the transmission risk of ARGs.The results of ARGs analysis showed mex F,bla CTX-M and sul1 were ARGs with the highest abundance,and sul1 might be considered as an indicator for the prediction of total ARGs.Network analysis indicated bla CTX-M and tet Q had the most potential genera hosts,and Proteobacteria and Firmicutes were predominant contributors of ARGs hosts at genus level.The discharge(effluent,sludge)included highly abundant ARGs(5.09×1014~4.83×1015 copies/d),integrons(1.11×1014~6.04×1014 copies/d)and potential pathogens such as Pseudomonas and Streptococcus,whose farmland utilization should be given more attention.In summary,aiming at the problems of low efficiency of bioresource utilization and ARGs transmission,this thesis revealed the microbial mechanisms of FW multichannel bioresource efficient utilization processes and their ARGs control in depth using different types of FW as the research object.Biogas residue was used to prepare BC and Fe Cl3-BC for the promotion of anaerobic digestion efficiency and ARGs reduction,B&M was used to achieve rapid compost maturation and ARGs reduction,microbial mechanisms of efficient organic matter conversion and ARGs transmission in Hermetia illucens feces composting were revealed,and the variation of ARGs and microbial communities in the biological treatment of FW leachate were elucidated.This thesis provides important guidance for the improvement of multichannel bioresource utilization efficiency of FW and the control of ARGs transmission.