Study On Screening Of Efficiency Straw-Degrading Strains And Preparation Of Decomposed Inoculants For Crop Straw

The total annual production of straw is very high in China.Straw as fertilizer returning in farmland is an important way to realize the utilization of agricultural waste resources.However,straw is rich in fiber,like cellulose hemicellulose and lignin that have complex structures and stable properties,resulting in a slow decomposition rate under natural conditions.Most of straw residues remain in the soil will affect the next crop growth,increase the risk of disease and insect pests.In order to improve the efficiency of returning straw decomposition,this study focusd on microbial degradation of straw carbon metabolic flow balance,the high efficiency lignocellulose degradation bacterium,lignocellulose degradation bacterium and straw decomposing intermediate metabolites bacterium build composite strains were screened and composed.The enzyme activity and substrate degradation rate of the composite strains were analyzed and the results are as follows:(1)Two strains of cellulose-degrading bacteria WS6-1 and WS6-2 were screened with crop straws as the limiting carbon source,which were identified as Stenotrophomonas sp.and chromobacter sp.respectively,by physiological,biochemical and molecular biology technique.The results of enzyme activity determination showed that WS6-1 had better ability to produce endonuclease glucanase and oxyglucosidase,with the activity of endocellulase,?-glucosidase of 325.7U and 146.5U respectively.The enzyme activities of endoglucanase,exocellulase and filter paper of strain WS6-2 were higher than that of strain WS6-1,about 351.2U/mL?274.9U and 284.0U,respectively.(2)Three low temperature resistant cellulose degrading bacteria(PS1-1,PS3-1 and SC6-1)were obtained by using crop straw as a restricted carbon source combined with cooling induction.PS 1-1 was identified as Acinetobacter sp.,PS3-1 and SC6-1 as Pseudomonas sp..The optimum enzyme production temperature for PS 1-1 was 25?,with the enzyme activity of endonuclease,exocellulase,?-glucosidase and filter paper 508.3U,410.4U,258.1U and 464.7U,respectively.At 5?,the enzyme activity remained 44.88%,60.46%,79.51%and 51.70%,respectively.The optimum enzyme production temperature for PS3-1 and SC6-1 was 20?,with the enzyme activity of internal glucanase,external glucanase,?-glucosidase and filter paper 404.9U,467.2U,263.5U,500.9U and 457.6U,397.0U,196.4U,99.2U,respectively.At 5?,the enzyme activity remained 48.2%-63.8%and 45.0-72.9%.(3)Two strains,named as YCl and YC2,were screened with the degrading capacity of ethanol,which was one of the main intermediate products during straw decompostion.Compared with YC1,the strain YC2 had higher ethanol degrading rate(0.224 mL/d),which was identified as Pediococcus sp.The results of the antagonistic test showed that the 6 screened strains were not antagonistic to the other 5 key functional strains in the decomposition process of straw(including lignin-degrading bacteria,thermophilic strains and biocontrol bacteria),and then the composite strain JX-1 was successfully constructed.(4)The combination of freeze-drying protectant was optimized by orthogonal test,and the optimal combination was 7%trehalose+ 2%twain-80.The composite JX-1 dry powder was successfully prepared,and the viable rate of dry powder was 84.81%,and the viable count of plate was above 1×109 cell,which met the technical requirements of the national standard for organic material rotting agent products(GB20287-2006).In addition,in order to shorten the stagnation period of bacterial agent application,the JX-1 dry powder agent was added with Urea(the quality of pure nitrogen content for dry powder 30%).Compared with three commercial straw decomposing inoculants,the degradation rate of corn straw by the trial production straw-decomposed inoculants wasincreased by 35.0%,66.3%and 76.8%,respectively.