Optimization Of Solid Compound Bacteria And Operating Conditions Of Household Kitchen Waste Biological Processor

The deepening of urban household garbage classification has significantly increased the amount of kitchen waste.Nevertheless,many cities in China are critically challenged by the kitchen waste treatment and disposal capacity.Therefore,using the household kitchen waste biological processor to treat kitchen waste in situ is a good way to alleviate this problem.The key factors influencing the practical application of household kitchen waste biological processor include the compound bacteria and operating conditions.Focusing on these key factors,this study which based on the previous work of our group investigated the optimization of solid compound bacteria and operating conditions,aiming to provide experimental basis for the popularization and application of household kitchen waste biological processors.The main results are as follows:1.Antagonistic effects between 18 strains were determined by plate face-off culture method and plate cross-scribing method,and the composition of solid composite bacterial agent for kitchen waste bioprocessor was optimized.2.Orthogonal experiment was used to optimize the storage strategy of the solid compound bacteriostatic agent,and the effects of water content（5%and 10%）,storage temperature（refrigerated and room temperature）and packaging mode（vacuum and atmospheric pressure）on the storage effect were explored.The results showed that vacuum packing at room temperature（5%moisture content）was the best storage approach and the effective viable bacteria was 1.1×10⁹ CFU/g dry weight.Temperature played a most significant role in the short-term（<90 d）storage of solid compound bacteria.The moisture content had the greatest influence on the preservation of solid composite bacteria agent,followed by packaging method and storage temperature during long-term storage（≥90 d）.3.The optimization performance of the household kitchen waste biological processor with the addition of different proportions of calcium oxide,zeolite and both was investigated by measuring indicators such as the kitchen waste reduction rate,p H,electrical conductivity（EC）,germination rate（GI）,effective viable bacteria count of the continuous dynamic aerobic composting process（28d/cycle）.The results indicated that the addition of calcium oxide could alleviate the acidification in the composting process and improve the reduction of kitchen waste treatment.The better calcium oxide addition ratio was 2%,with the p H of compost maintaining above 6.5,the wet weight reduction rate was 92.7%,and the total dry matter reduction rate reached 42%.The addition of zeolite decreased the EC of compost and improved the maturity of compost products.The better zeolite addition ratio was 8%,and the seed GI of the final compost product was 71%.In the experimental group,the wet weight reduction rate reached 92%,the total dry matter reduction rate reached 53%and the seed GI of the compost product was 71%,indicating that the reduction rate of kitchen waste treatment and the maturation degree of compost products were synchronously improved.4.Based on the metagenomics sequencing results of the compost samples at the beginning and end of the experimental group of calcium oxide zeolite co-addition（running for 28 d）,the mechanism of microbial action in the composting process of kitchen waste biological processor was analyzed from a microscopic perspective.The analysis of the dynamics of microbial community composition showed that bacteria were the main microbial consortia during the biotransformation of kitchen waste.Firmicutes and Lactobacillus were dominated in the microbiome at the end of operation.The relative abundance of fungi decreased significantly in the later compost period,and only Mucor and Rhizopus remained.According to the prediction analysis of metabolic pathways,the dominant metabolic pathways in beginning and ending samples were membrane transport,amino acid metabolism,cofactor and vitamin metabolism,energy metabolism,and signal transduction.The relative abundance ofβ-glucosidase andβ-xylosidase,the key enzymes of cellulose and hemicellulose degradation,were significantly debased after operation.Besides,accounting for the ash（non-organic matter in dry matter）in the co-addition experimental group,and the ash majorly came from the added calcium oxide and the non-organic matter part of the daily simulated kitchen waste.Organic matter was eliminated during composting mainly in the form of converting to CO₂ and H₂O.