Construction Of Efficient Cellulose-degrading Bacteria Agent And Its Application In Corn Straw Composting

As a way of straw resource utilization,straw composting treatment can transform straw into organic fertilizer under the action of microorganisms,and its application in farmland can improve soil fertility and structure.However,straw,as a typical cellulosic material,is difficult to degrade,which leads to problems such as long fermentation period and poor quality of compost products.Therefore,in this study,high-efficiency cellulose-degrading bacteria were screened and high-efficiency cellulose-degrading compound bacteria were constructed to accelerate compost maturity and improve compost product quality.And at the same time,the change of the physical and chemical properties in the composting process were analyzed,and the bacteria community diversity were researched in the composting process.The changes of humus in compost were studied to reveal the potential influence mechanism of exogenous cellulose degrader on humus synthesis,and provide a theoretical basis for the influence of exogenous cellulose-degrading bacterial agents on humus synthesis during composting.The main conclusions are as follows:（1）Four strains with high cellulase production（WS-1,WF-8,WF-10 and WF-11）were finally screened by Congo red staining test,filter paper strip degradation test and cellulase activity assay test.Identified by molecular biology,Ws-1,WF-8,WF-10 and WF-11 were Bacillus cereus,Bacillus Subtilis and Streptomyces ansochromogenes and Bacillus lincheniformis,respectively.（2）A group of compound agents（WS-1+WF-8+WF-10+WF-11）with high cellulase activity was screened out by measuring and comparing the activity of CMCase and filter paper enzyme（FPA）of compound agents in each group,which was denoted as HD.Then,CMCase was used as the optimization index to optimize the fermentation medium and the fermentation conditions for producing enzyme of HD,and the optimal medium for producing enzyme was determined as follows:Straw powder 15 g,（NH₄）₂SO₄4 g,KH₂PO₄1.0 g,Mg SO₄·7H₂O 0.3 g,Na Cl 0.1 g,Ca Cl₂0.1 g,Fe Cl₃0.01 g,dd H₂O 1000 m L,the optimal fermentation conditions were as follows:temperature 34℃,inoculation amount 5%,time 6 d and p H7.2,the cellulase activity increased 1.45 times compared with before optimization.（3）The study on the physical chemical properties of corn straw compost inoculated with compound bacterial agent HD showed that,compared with the uninoculated control,adding exogenous cellulose-degrading bacteria shortened the composting period by 7 days.After composting,the degradation rates of cellulose and hemicellulose in the compost inoculated with compound bacteria agent were 78.89%and 89.04%,which were 10.60%and 9.29%higher than those in the control group,respectively.The addition of exogenous cellulose-degrading bacteria promoted the degradation of cellulose and hemicellulose,and accelerated the mineralization process of compost.In addition,the addition of exogenous cellulose-degrading bacteria increased the humus content of compost products by 15.85mg/g,which promoted the humification process of compost.（4）Analysis of bacterial community succession at different stages in compost by high-throughput sequencing technology.The results showed that the inoculation of exogenous cellulose-degrading bacteria increased the richness and diversity of bacterial community during compost fermentation.The redundant correlation analysis of physical and chemical factors,humus and bacterial communities in compost indicated that the addition of exogenous cellulose-degrading bacteria stimulated the potential function of the bacterial communities.Co-occurrence network analysis showed that the addition of exogenous cellulose-degrading agent enhanced the network complexity and the interactions among bacterial communities during composting.The structural equation model（SEM）results indicated that exogenous cellulose-degrading agent strengthened the biodegradation pathway of organic matter and the humus biosynthesis pathway,and enhanced the driving force of humus synthesis.