Dynamic Features On Spectra Of Dissolved Organic Matter And Microbial Community During Full-scale Black Soldier Fly Larvae Bioconversion For Biodegradable Domestic Waste

With the rapid development of the world economy and the process of urbanization in rural areas,the production of biodegradable domestic waste showed an increasing trend year by year,but the bottleneck of sustainable treatment technology is emerging.Due to its safety,high economic efficiency and environmental friendliness,the black solider fly larvae（BSFL,Hermitia illucens L.）bioconversion technology for waste has attracted the attention of many researchers.However,the current research on the effectiveness and mechanism of full-scale BSFL bioconversion was insufficient,which restricted the re-innovation and technological upgrading of technology.Dissolved organic matter（DOM）is the core component in the process of decomposition,transformation and synthesis of organic matter by microbial.It is also the main object to study the efficiency and mechanism of BSFL bioconversion technology.Therefore,based on the actual conditions,this study expounded the dynamic processes and relationships of the physico-biochemical properties of the BSFL reactor,and then discussed DOM chemical composition of the material and the succession of the microbial community structure in the bioprocess system.（1）After bioconversion by BSFL,the basic physiochemical indexes and enzyme activity indicators of the experimental group（BV）were significantly different from those of the natural stacking group（NC）:the temperature of the BV rose rapidly from26.3°C to 50°C,and the water content increased from 71.6%to 61.1%;the p H increased from 4.59 to 7.94.DOM,TON,TC,C/N in stack material under BSFL treatment decreased by 51.5%,19.9%,18.3%,13.5%,respectively.Enzyme activity indicators such as catalase,lipase,protease,invertase,urease and cellulase were significantly higher than those of the NC,increased by 56.3%,28.8%,26.5%,15.8%,14.5%,9.28%respectively.Black soldier fly larvae accelerated the bioconversion process of bio-degradable domestic waste,and significantly improved the microbial metabolic capacity of carbon,nitrogen,organic matter,refractory substances and fats.（2）The UV-vis absorption parameters S_280-400,SUVA₂₅₄,SUVA₂₈₀,A_226-400 and E₂₅₃/E₂₀₃ of DOM in the stack material increased by 398%,230%,186%,143%,40.9%respectively.The analysis of 3D-EEM showed that the peak intensity of the region characterizing tyrosine-like,tryptophan-like and soluble microbial products decreased significantly,and the peak intensity of the region characterizing humus increased significantly.The position and intensity of the characteristic peaks in FT-IR changed significantly.The indexes such as 1636/2930,1636/1578,1636/1050 and 1636/1077increased by 39.8%,37.1%,10.7%,8.87%respectively.The result indicated that the DOM components of the stack materials are mainly from microbial sources,but the protein,fat,polysaccharides and cellulose were degraded by BSFL and microorganisms.The content of aromatic compounds increases rapidly,and the degree of humification and stabilization of the stack materials has increased significantly.（3）The structure of the stack microbial community changed significantly at all levels.αdiversity analysis showed that the richness of microbial community decreased,but the diversity and evenness increased significantly.βdiversity analysis showed that the interpretation rate of Weighted Uni Frac reached 70.3%,which was significantly different between groups.The prediction results of the metabolic function showed that the decomposition of hydrocarbons,cellulose,lignin,and nitrogen cycle were strengthened,and the human pathogenic bacteria and parasites bacteria were significantly reduced in BV,indicating that the BSFL can not only speed up the composting process,but also improve the safety of composting.（4）Spearman correlation analysis showed that environmental factors and DOM spectra indexes were significantly correlated with microbial community diversity.Among DOM spectra indexes,SUVA₂₅₄,SUVA₂₈₀ and HIX were significantly positively correlated with the everness and diversity indexes of bacterial community,while BIX and I_A/I_C were on the contrary;In terms of species composition,SUVA₂₅₄,SUVA₂₈₀ and HIX were strongly positively correlated with the abundance of Clostridia and Actinobacteria,while BIX and I_A/I_C were strongly positively correlated with the abundance of Bacilli.