Screening Of Low Temperature Cellulose Degrading Microbes And Evaluation Of Applied In Composting

With the rapid development of large-scale and intensified animal husbandry,the number of livestock manure has increased dramatically,causing serious environmental pollution and resource waste.Aerobic composting is an effective method for the harmlessness and resource utilization of livestock manure,which has been widely used and researched.In the cold northeast region of China,low winter temperature and long duration lead to slow degradation rate of accumulated livestock and poultry manure,slow start of composting temperature rise,long fermentation cycle and low fertilizer efficiency of fermented products,which limit its large-scale application.The purpose of this research is to screen low-temperature bacteria and apply them in composting,provide solutions to improve the efficiency of composting fermentation under low temperature conditions.In this study,through screening low-temperature cellulose-degrading strains from low-temperature cow dung stool,identification of its strains and cellulase activity determination,the low-temperature starting compound bacterial agent was prepared,and the cold-tolerant microorganisms had better low-temperature biological activity.It can accelerate the heating up of the pile,shorten the fermentation period and improve the quality of compost.Using fresh cow dung and straw as compost raw materials,the degree of composting accessory was judged by the changes of the parameters of the compost during the composting process.The main research contents and results are as follows.(1)Using cow dung and soil taken in winter as experimental materials,11 strains of cellulose-degrading bacteria were screened by the Congo red staining method.3,5-dinitrosalicylic acid colorimetry(DNS)method was used to determine the standby dominant strains of low temperature compound cellulose-degrading bacteria,named YSX-3,YXS-7,YST-18,respectively.The enzyme activity was 88.84U/mL,100.18U/mL,77.15U/mL.(2)After morphological identification,physiological and biochemical analysis and 16 S r DNA sequencing analysis,strains YSX-3,YXS-7 and YST-18 were all Pseudomonas bacteria.The similarity between strain YSX-3 and Pseudomonas taetrolens is 99%,strain YSX-7 has the highest similarity with Pseudomonas versuta,and strain YST-18 is closely related to Pseudomonas fragi.(3)Preliminary study on enzyme production activity of low-temperature cellulose degrading strains YSX-3,YSX-7 and YST-18,the most suitable growth conditions were measured to be 4%inoculum,72 hours of culture time,culture temperature of 10℃,and p H of 7.(4)In this experiment,the 3 strains of low-temperature degradation bacteria were screened for antagonism.The results showed that there was no inhibitory effect among the 3 strains and could be co-cultured.So the strains YSX-3,YSX-7 and YST-18 were mixed in Cultivation and preparation of low-temperature degradation bacteria under optimal conditions,cellulase activity was determined to be 112.51U/mL.(5)On the basis of single factor experiment,3 strains of mixed bacteria were selected to design the response surface experiment of low-temperature cellulose inoculants to optimize the enzyme production conditions.The optimal conditions for enzyme production were determined to be 4% inoculum,culture time 71 h,and culture temperature 9℃,the p H value is 6.5,and the measured low-temperature cellulase activity is 130.21U/mL,which is 1.30 times higher than before optimization.(6)A low-temperature aerobic composting experiment was carried out using cow dung and straw in an environment of about 10℃,and 3 equal-volume mixed bacterial liquids with an inoculum amount of 5% to the pile.The results showed that the temperature of the reactor began to rise on the 2nd day,and reached the highest temperature of 65.9℃ on the 10 th day,and the high temperature period was maintained for a total of 12 days;The control group reached the highest temperature of 38.3℃ on the 12 th day,and did not enter the high temperature period.At the end of composting,the water content of the pile in the experimental group was 28.21%,the C/N was15.08,the organic matter content was 53.26%,the GI value was 93.37%,and the cellulose degradation rate was 46.21%.It shows that in cold regions,the selected low-temperature compound bacteria can accelerate the compost maturity process,shorten the fermentation cycle,and improve the quality of the compost.All indicators are in line with my country’s standards for harmless composting.