Preparation,Preservation,and Properties Of Efficient Liquid Bacteria In Aerobic Composting Of Biogas Residue Of Kitchen Waste

Kitchen waste mainly refers to the scraps from food processing and edible residues in school,canteens and catering industry produced.The output of kitchen waste has increased rapidly in recent years.How to deal with kitchen waste efficiently and realize the recycling of solid waste is of great significance to achieve emission peak and carbon neutrality.Aerobic composting technology is one of the most effective ways to treat kitchen waste,However,there are some problems in the actual composting operation,such as insufficient amount of high-temperature and high-efficiency composting degrading bacteria and difficult to preserve for a long time.This study the high efficiency degrading bacteria were enriched,separated and purified under high temperature conditions from anaerobic digestion biogas residue of kitchen waste.and Microbial agents were preparation by using isolated strains and enriched bacteria.The preservation conditions of the microbial agent were optimized,and the microbial agents were applied in the aerobic composting of kitchen waste,The specific conclusions are as follows:（1）Enrichment,separation and purification of efficient composting degradation bacteria and preparation of efficient liquid bacteria.The biodegradable bacteria were enriched by biogas residue of food waste anaerobic digestion.The enrichment lasted for 39 d for 4 cycles.The degradation rate of organic matter and degradation rate increased continuously during the enrichment process,the degradation rate reached89.3%,and the COD_Cr concentration decreased continuously.The lowest COD_Crconcentration was 1800.3 mg/L.Different strains can produce proteases,hydrolases and organic acids,which can improve the organic matter degradation rate of aerobic composting and maintain the acid-base balance in the composting process.A total of 25strains were isolated and purified.The isolates were identified as Clostridium spp,Brevibacillus spp,Oceanobacillus spp,and Paenibacillus,respectively Sphingoba-cterium spp,α-Proteobacteria spp.,β-Proteobacteria spp,γ-Proteobacteria spp,Pseudoxanthomonas spp,Pigmentiphaga Daeguensis spp,Cytobacillus spp,Desulfitobacterium spp.Among them,Clostridium,Bacillus Brevibacillus agri andα-proteus were selected.Castellaniella fermenti,Thioprofundum Hispidum,Alcaligenaceae bacteria,Pigmentiphaga After 96 h of degradation,the number of viable bacteria increased by about 8 orders of magnitude compared with the initial enrichment,and the organic matter degradation rate reached 91.3%.（2）Optimization of storage conditions for efficient liquid bacteria.Suitable culture medium preservation conditions can keep the character of protein-degrading bacteria stable during storage,and then slow down senescence,degeneration and death.In this experiment,the optimal single factor storage conditions were as follows:the amount of liquid in full bottle,the amount of calcium carbonate 3 g/L,the amount of peptone and glucose 2 g/L,and the optimal p H 6.After 3 months of storage,the maximum number of viable bacteria was 6.09×10¹² when the amount of glucose 2 g/L.The lowest viable bacteria count was 7.30×10⁸ when the calcium carbonate supplemental level was 3 g/L.The optimal preservation scheme is glucose 2.5 g/L,p H 5.5,calcium carbonate is 3 g/L and peptone 2.5 g/L.The number of viable bacteria was 5.30×108 and the degradation rate of COD_Cr was 53.2%after being stored at room temperature for 7 months.（3）Study on the effect of application of preserved liquid microbial agent in aerobic composting of biogas residue of kitchen waste.Inoculation of high temperature and high efficiency liquid aerobic compost preservative agent in kitchen waste aerobic compost can prolong the high temperature period of compost,adjust the moisture content and p H of compost,and shorten the compost maturity period.With the continuous composting,the color of compost material gradually changed from egg yellow to black brown.The compost temperature first increased and then decreased,and the high temperature period lasted for 7 days.The maximum temperature of 57.2℃was 8.8℃higher than that of the control group.At the end of the compost period,the temperature gradually stabilized to room temperature,and the compost maturity time reached 35 days,while the control group was still not mature at 35 days.The p H value of the control group was higher than that of the experimental group before the 16th day of composting.On the 35th day of composting,the p H value of the experimental group was 8.27,1.25 higher than that of the control group.The moisture content decreased gradually with the change of time.The moisture content in the bacterial agent group was lower and the degradation rate was faster than that in the control group,and the moisture content was 14%lower than that in the control group after 35 days of composting.In addition to total protein,the contents of total nitrogen,available phosphorus and available potassium were more than 5%before and after composting,and all the indexes reached the standard of composting.（4）Microbial community structure changes of samples at different composting stages during the application of liquid microbial agent.The diversity and abundance of bacterial community in the compost materials at different composting periods were the highest at DF₀ and DF₁₇,and the compost materials at different composting stages contained 8 Phyla,20 Classes,33 Orders,35 Families,53 Genera and 72 Species.The dominant Phyla were Firmicutes,Bacteroidetes,Proteobacteria,Patescibacteria and Synergistota.The dominant bacteria were Bacteroidia,Gammaproteobacteria,Bacilli,Clostridia,Dojkabacteria,Limnochordia and Synergistia.The dominant bacteria are Bacillus,Ulvibacter,Alcanivorax,Sphingobacterium,Pediococcus and Paenalcaligenes.The proportions were 25.29%,19.44%,15.19%,30.84%,10.16%and10.22%,respectively.Bacillus and Sphingobacterium are highly degraded bacteria identified by molecular biology in the early stage,accounting for 25.29%and 30.84%of the total in the compost.Among the high-temperature dominant bacteria with relative abundance>1%,Bacillus,Oceanobacillus and norank＿f＿＿Fodinicurvataceae were highly degraded bacteria in the early preparation,accounting for 11.98%,3.05%and1.04%,respectively.Bacillus,Clostridium＿sensu＿stricto＿18,accounted for 11.98%and 3.05%,respectively.