The Synergistic Effect Of Earthworm And Microbiota On Vermicomposting Process

Vermicomposting is a process of stabilization,harmlessness and humification of unstable organic matter in sludge by the interaction between earthworms and microbiota(microfauna and microbe).As the highest nutrient level in the food web,the physiological activities of earthworms directly or indirectly affect the number,community structure and activity of microbiota,and the microbiota in turn can serve as the food for the growth and reproduction of earthworms.They interact and influence each other,which affects the vermicomposting process.Therefore,in order to explore the synergy of earthworms and microbiota and the effect on the composting process,this research set up the control group and treatment group respectively to study(1)the characteristics of the earthworm and microbiota(2)the physical and chemical properties of sludge(3)the content,ultraviolet-visible spectral characteristics,the three dimensional fluorescence spectrum structure of humus and its components to analyze the physical and chemical properties and structure changes in the process of vermicomposting,thus we can reveal the degradation mechanism in the system.The results of this study show that:(1)Earthworms grow well in the sludge;There are four main types of microfauna in the sludge:Ciliats,Tcstatc amocbac,rotifers and nematodes.Among them,the number of Ciliats die rapidly in the early stage of vermicomposting.The number of Tcstatc amocbac decrease with the composting process,and the earthworms have a certain inhibitory effect on the Tcstatc amocbac.The number of rotifers decline;The number of nematodes fluctuat;The number of microbiota(bacteria and fungi)change with the process of vermicomposting,and the biomass and physicochemical properties of earthworms are closely related.Earthworms decrease the diversity and richness of bacterial community,but increase the diversity and richness of fungal community.The dominant bacteria phylum in bacteria community accounting for 80.51%-89.89%,including Proteobacteria,Bacteroidetes,Chloroflexi and Actinobacteria.The dominant phylum of fungal community structure are Ascomycota,Basidiomycota and Chytridiomycota,which accounted for 65%?86%.The presence of earthworms reduce the activity of microbiota(microfauna,microbe).(2)The synergistic effect of earthworms and microbiota promote the degradation of organic matter(OM)and increase the contents of nitrate nitrogen and available phosphorus to a great extent;Principal component analysis(PCA)of physical and chemical factors show that the synergistic effect of earthworms and microbiota could promote the mineralization of organic carbon in the early stage of vermicomposting and accelerate the mineralization of organic nitrogen by promoting ammonification and nitrification in the middle and late stage of vermicomposting.Redundant analysis(RDA)of physical and chemical factors and microbiota show that the change of microbial community is correlated with NO3~--N and OM,and NO3~--N is directly proportional to Proteobacteria,Actinobacteria,Chytridiomycota,and in negatively proportional to Firmicutes,Chloroflexi,Nitrospirae Acidobacteria,Bacteroidetes,and Ascomycetes.OM is directly proportional to Mycobacterium,Chloroflexi,Acidobacteria,and Bacteroidetes,and inversely proportional to Basidiomycetes,Proteobacteria,and Actinomycetes.Proteobacteria,Actinobacteria and Chytridiomycota are related to the conversion of nitrogen and phosphorus,Firmicutes,Nitrospirae and Acidobacteria are related to the degradation of organic matter,and Bacteroidetes and Ascomycota are related to the conversion of carbon.(3)The synergistic effect of earthworms and microbiota reduce the content of extractable humus(HE),fulminic acid(FA)and humic acid(HA)in sludge;The characteristic curves of UV-Vis spectrum and each parameter show that under the synergistic action of earthworm and microbiota,the degree of aromatization of urban sludge humus decreased,the degree of molecular condensation decrease and the molecular weight decrease.Therefore,earthworm treatment of urban sludge does not humic the organic matter in the sludge into macromolecules,but further decompose the relatively difficult to degrade substances.Correlation analysis of earthworm treate urban sludge microbiota and UV spectrum parameters show that the genera Terrimonas?norank?f?Intrasporangiaceae,Galactomyces?norank?o?Pezizales?norank?o?Sordariale?norank?p?Chytridiomycota?unclassified?o?Saccharomycetales?unclassified?p?Ascomycotahavedifferentcorrelationswith SUV254,SUV280,E253/E203,E253/E220,A226-400,S275-295,S350-400 and other parameters.Most of these genera are related to the degradation of macromolecules such as humus,benzene ring and aromatic compounds.Therefore,the synergistic effect of earthworm and microbiota improves the further biodegradation ability of macromolecules.(4)The three dimensional fluorescence spectra show that with the increase of composting days,soluble organic matter(DOM)in the class of fulvic acid,humic acid area gradually reduce,extractable humus,soluble microbial products have no obvious changes in aromatic increased protein substances,fulvic acid in the solubility of microbial by-products,largely disappeared after composting,humic acid by-product to reduce solubility of microbiota.The synergistic effect of earthworms and microbiota promote the synthesis of aromatic protein substances and microbial byproducts in DOM,aromatic protein synthesis in HE,and degradation of soluble microbial byproducts in FA and HA.