Screening,Metabolite Analysis And Evaluation Of Straw Degradation Effect Of Low-temperature Lignin Degrading Bacteria

As the main area of breeding and agricultural development in northern China,a large amount of livestock manure and corn stalks and other by-products are produced every year.Lignin is the main reason to limit the effective natural degradation of these by-products.In addition,the longer autumn and winter in northern China and the lower temperature make the natural degradation of feces and straw more difficult.Therefore,it has important research significance to screen high-efficiency lignin degradation bacteria under low temperature environment to improve the degradation rate of lignin and straw.Aiming at the environmental problems caused by lignin resource utilization in cold regions,In this experiment,a strain of efficient lignin degrading bacteria was isolated and screened.The enzymatic production conditions,enzymatic characteristics and metabolites of lignin degradation were optimized.Finally,the degradation function of straw was studied through solid-state fermentation.The main research contents are as follows:1.Isolation and identification of low temperature lignin degrading bacteriaFive strains of low-temperature lignin degrading bacteria were isolated from permafrost soil and cattle dung under the long-term natural decaying leaves of broad-leaved forest by aniline blue primary screening and enzyme activity determination.Among them,strain LS-1 has the best enzyme production effect,Lip enzyme activity was 20.68 U/m L,Lac enzyme activity was 8.71 U/m L,Mnp enzyme activity was 31.71 U/m L.LS-1 was determined to be Stenotrophomonas maltophilia by colony morphology observation and 16s r RNA molecular biology sequencing.2.Optimization of enzyme production conditions of strain LS-1The enzymatic production conditions were optimized by single-factor screening and response surface experiment.The results showed that when LS-1 uses lignin as the sole carbon source and peptone as the sole nitrogen source,the p H is 8.0,the temperature is 15?,and the time is 3 days,the lignin-degrading enzyme activity is the highest,Lip enzyme activity was 24.49 U/m L,Lac enzyme activity was 9.78 U/m L,Mnp enzyme activity was 50.86 U/m L.3.Study on the enzymatic properties of strain LS-1 and the effect of inducer on enzyme activityThe enzymatic properties of Lip?Lac and Mnp were studied on the basis of optimizing enzymatic production conditions,the optimal temperature of Lip and Lac is30?and has good thermal stability,while Mn P is 50?and has poor thermal stability.The most suitable environment for the three enzymes are acidic conditions,Lip and Mnp are most suitable for p H 5.0,Lac is the most suitable for p H 4.0.Studies on the effect of inducers on enzyme activity showed that,Eugenic acid(0.75?1.75 mmol/L)and Cu²⁺(1 mmol/L)had obvious promotion effect on Lac,Mg²⁺(0.75 mmol/L)and Tween 20(0.5%)can obviously promote Lip and Tween 20(0.1%?0.5%)had a significant promoting effect on Mnp.4.Analysis of metabolites of lignin degradation and evaluation of straw degradationAnalysis by GC-MS,some alcohols,phenols and acids appeared in the metabolites of LS-1 degradation of lignin,some esters and aldehydes were also metabolized in the degradation process,and the contents of the other compounds produced changed compared with the control group.After 20 days of low temperature straw degradation test,the weight loss rate of straw in the test group was 18.85%,and the lignin degradation rate was 36.14%,which was about 3 times and 6 times higher than that in the control group,respectively.