Study On Aerobic Composting Of Sorbic Acid By-products

Sorbic acid is internationally recognized as a relatively safe food additive,which is widely used in dairy products,food and beverage,cosmetics,tobacco,pet poultry feed and other industries.With the rapid growth of sorbic acid market demand,the production of sorbic acid by-products has increased rapidly.The composition of sorbic acid by-products is complex,containing antibacterial substances such as crotonaldehyde,acetic acid,hydrochloric acid,sorbic acid polyester,ethanol,sorbic acid and its isomers,how to reasonably realize its harmless and resourcefulness is an urgent technical problem to be solved.Aerobic composting technology has been widely used in the resource treatment of organic solid waste because of its safe,economic,effective and environment-friendly characteristics.Based on this,in this study,sorbic acid by-products,cow dung and straw were used as raw materials,firstly separates and screens the tolerant strains from the sorbic acid by-products composting system,clarifies the formulation of bacterial agent through molecular identification,then strengthens the aerobic composting effect of sorbic acid by-products through bacterial agent addition combined with Fenton pretreatment in order to investigate the feasibility of aerobic composting technology to realize the resource utilization of sorbic acid by-products,and provides technical support for further scaling up and industrialization.The specific research content and results are as follows:（1）Screening and identification of microbial strains for aerobic composting of sorbic acid by-products.Sorbic acid by-products,cow manure and corn straw were used as raw materials for mixed aerobic composting,and 16 tolerant strains were obtained from the pile by isolation and screening,according to the molecular identification results,the microbial agent for sorbic acid by-products aerobic composting consisted of 10 strains,which were Enterococcus faecalis,Lysinibacillus xylanilyticus,Bacillus velezensis,Lysinibacillus macroides,Bacillus tequilensis,Bacillus amyloliquefaciens,Bacillus subtilis、Bacillus aerius,Bacillus mojavensis,Lysinibacillus mangiferihumi.（2）Optimization of mixed fermentation conditions of microbial agents for aerobic composting of sorbic acid by-products.The above strains were mixed in equal proportion to optimize the mixed fermentation conditions.The single-factor shaking flask experiment results showed that the optimized condition is that the carbon source is 5 g/L maltose,and the nitrogen source is 5 g/L yeast powder.The results of orthogonal experiment showed that when p H was 7.0,rotating speed was 140 r/min,and inoculation amount was 6%,the biomass of fermentation broth was the highest,2.91 g/L.The optimized results of batch feeding experiment in 3 L fermentation tank showed that the feeding time of carbon source was 9 h,the feeding concentration was 0.4%,and the number of viable bacteria reached 23 billion CFU/m L after 24 h fermentation,which was 75.57%higher than that without feeding,which can significantly reduce the cost of adding bacterial agents in aerobic composting.（3）A preliminary study on the optimization and mechanism of Fenton pretreatment sorbic acid by-products process.The optimized Fenton pre-treatment conditions are:the dosage of H₂O₂ was 1 time of COD mass,the molar ratio of H₂O₂ to Fe²⁺was 20,the p H was3.0 and the reaction time was 120 min,and the antibacterial rate of the product was reduced from 93.28%to 27.71%.The results of GC-MS analysis showed that sorbic acid and 2,4-Hexadienoic acid,ethyl ester were the main components of sorbic acid by-products,with the relative contents of 64.81%and 10.56%respectively,and both of them could be oxidized by strong oxidizing·OH generated from Fenton reaction and converted into small molecule organic acids and alcohols,including acetic acid,ethanol,etc.,which were the main reasons for the decrease of sorbic acid by-products inhibition rate and were beneficial to the smooth progress of subsequent aerobic composting biological treatment process.（4）Aerobic composting of sorbic acid by-products was strengthened by adding bacteria and pretreatment.Pretreatment combined with bacterial agent could greatly improve the mixed aerobic composting process of sorbic acid by-products.Compared with the control group,the maximum temperature of pretreatment combined with bacterial agent addition group increased by 19.7°C,the degradation rate of organic matter increased by 10.91%,and the degradation rate of soluble organic matter increased by 32.96%.At the end of composting,the pretreatment combined microbial agent addition group had the lowest C/N ratio of 9.47and the highest seed germination index of 115.65%.The composted products met the requirements of maturity standards,and from the technical point of view,it is feasible to use bacterium-added combined pretreatment to realize the resource utilization of sorbic acid by-products aerobic compost.