Development And Performance Study Of High-efficiency Microbial Agent For Aerobic Composting Of Kitchen Waste

Kitchen waste is mainly consist of discarded fruits,vegetables and leftover food.Kitchen waste is rich in organic substances such as starch,protein,cellulose and fat.These substances are perishable easily,and easily stir up bacteria and emitted disagreeable smell.Kitchen waste prevent risks to both human health and the environment.Under the stress of global energy shortages,high-quality organic fertilizer can be obtained by aerobic composting of kitchen waste with microbial agents,which were important for achieving emission peak and carbon neutrality.In this study,the aerobic compost material of kitchen waste was used as the bacterial source,and the high efficiency degrading bacteria were enriched,separated and purified under high temperature conditions.Microbial agents were preparation by using isolated strains and enriched bacteria.The cultivation and storage conditions of the microbial agent were optimized,and the microbial agents were applied in the aerobic composting of kitchen waste.This paper was in order to provide support for the practical application of the composite microbial agent in the aerobic composting of kitchen waste Conclusions are as follows:（1）In this study,the activity and quantity of high efficiency degrading bacteria increased significantly with the increase of enrichment time.,the enrichment process lasted 4 cycles and a total of 34 days.The content of CODcr was about 18000 mg/L in the initial enrichment medium,and it stabilized at about 3500 mg/L after the degradation was completed.After culturing for 3 d in the final enrichment medium,the CODcr content reached a stable value,and the organic matter degradation rate reached71%.Then,7 strains of high efficiency degrading bacteria were isolated,purified and screened and numbered according to No.1-7,which belong to Bacillus＿thermophilus,Clostridium＿isatidis,Luteimonascompost,Aneurinibacillus＿sp.,Paenibacillus＿dendritiformis,Trueperar adiovictrix,Ureibacillus＿thermosphaericus.The strain No.3,No.4 and No.5 showed better degradation effect,of which strain No.4 had the best degradation effect,showed high degradation ability during the passaging process.The strain No.4 has the characteristics of salt tolerance and can degrade high concentration oils and fats,which can promote the process of aerobic composting of kitchen waste effectively.The strain No.3 has the function of degrading protein,and the strain No.5 can degrade cellulose efficiently.（2）In this study,three microbial agents were prepared by using the enriched bacterial liquid at the end stage and the screened high-efficiency strains.The enriched bacterial liquid at the end stage was the A microbial agent,the mixed bacterial solution of the 7 high efficiency degrading bacteria was the B microbial agent,and the 7 high efficiency degrading bacteria+the enriched bacterial liquid at the end stage was C microbial agent.The three microbial agents had degradation effect on kitchen waste,but the richer the microbial community structure,the better the degradation effect on kitchen waste with complex components.Among them,C microbial agent had the best degradation effect.When inoculated into kitchen waste,the degradation rate for 48 h could reach 55.5%,the degradation effect of A microbial agent was lower significantly than that of the other two groups,and the degradation rate of cultured for 48 h was only35.5%.In addition,the screened high-efficiency bacteria could show higher activity after mixing with the enriched bacteria solution at the end stage.The species with relative abundance of more than 10%in A microbial agent were uncultured＿bacterium,Symbiobacterium＿thermophilum and Tepidimicrobium＿xylanilyticum,in the B and C microbial agent,the Aneurinibacillus＿sp.,Paenibacillus＿dendritiformis and Luteimonas compost were more abundant.（3）In this study,the carbon source and concentration,nitrogen source and concentration,initial p H value and trace element type and concentration of the medium were optimized.The optimized medium components were tryptone 12 g/L,glucose 1.5g/L,beef meal 3 g/L,sodium chloride 5 g/L,Fe³⁺40 mg/L,and the p H value was 5.5-7.5.Compared with before optimization,the number of cells in the culture medium increased by 34.1%,and the degradation rate of organic matter increased by 16.9%after culturing for 48 h.In addition,it was important to select the appropriate additive during the preservation process.Glucose was selected as the preservation additive of C microbial agent because of its best preservation effect,the survival rate of the microbial was 52%after 6 months of preservation.The second was maltose,which survival rate was 44.7%after 6 months of preservation.Besides,compared with control group,and the starch had no obvious effect on the preservation effect of the microbial agent,which were 39.3%and 39.2%after 6 months of preservation.Furthermore,the number and activity of microorganisms in the microbial agent were degraded significantly after 3months of storage.It was necessary to activate to improve the effect of the agent before using that.（4）In this study,the C microbial agent could improve the composting effect and promote the composting process.The C microbial agent could promote the appearance and color change of the compost material,the material was dark brown in the experimental group after composting,and the texture was soft and loose,and the porosity was low.The heating time of the compost material was shortened,and the duration of the high temperature stage was prolonged.In a laboratory test,the temperature of the material exceeded 50°C on the 6th day of fermentation in the experimental group,and the high temperature duration was 6 days.While in a pilot laboratory test,the temperature of the material exceeded 50°C after 2 days of composting,which was 4 days earlier than that in a laboratory test and 6 days earlier than that in the control group.It could promote the reduction of moisture,the moisture of the materials decreased more in the experimental group during the composting process,and the p H value of the materials met the requirements after the composting process.In addition,the total content of nutrient and organic matter of all the treated composts samples in this experiment were higher than the values specified for organic fertilizers in the national standard.（5）In this study,it was found that the bacterial community structure of composting samples was significantly different in different stages.Adding C agent could increase the proportion of high-temperature bacteria in the material.The number of high temperature bacteria was 162.5%higher than that of the control group in the high temperature stage,and the number of high temperature bacteria also was 81.2%higher than that of the control group at the end of composting.In addition,the high temperature condition of the material was conducive to killing the large intestine group of feces and ensuring the hygienic index of the compost product.The high-throughput sequencing results showed that the high-efficiency bacteria in the C agent could participate in the aerobic composting process of kitchen waste,and it had an absolute advantage in the composting material in the microbial community structure.At the phylum level,the main dominant bacteria were Firmicutes and Proteobacteria.At the class level,the dominant bacteria are Bacilli,γ-Proteobacteria,α-Proteobacteria,Bacterodia and Aneurinibacillus.At the species level,the high-efficiency bacteria in the high-temperature stage were higher significantly than those in the early stage of composting.The high-efficiency bacteria added in this experiment accounted for 12.5%,68.3%and31.1%respectively in the three stages of composting.The main dominant bacteria were Aneurinibacillus＿sp.,Ureibacillus＿thermosphaericus,Paenibacillus＿dendritiformis,and Trueperar adiovictrix in the high temperature stage and the end of composting.The ratios were 35.4%,11.2%,5.6%and 5.2%in the high temperature stage,and the ratios were 11.3%,5.4%,4.6%and 4.5%after composting,which were all high efficiency degrading bacteria screened in this experiment.That can be seen that the high-efficiency bacterial agent prepared promoted the aerobic composting process of kitchen waste in this experiment.