The Screening Of Straw Degrading Bacteria And Optimization Of Drought Tolerance

Returning crop straw in situ can improve the comprehensive utilization of straw,and reduce the negative impact of straw on the environment,at the same time,it can also improve the physical and chemical properties of the soil.However,the speed of straw returning is slow and the straw degradation efficiency is low,which may generates many adverse effects for the soil and agricultural operations and limit the promotion of straw returning.In this study,we mainly screened high-efficiency straw degrading bacteria and improved the drought-tolerant of the strains.Then the strains are made for fungicide and validated by pot experiment.The main results of experiment are as follows:1?High-efficiency straw-degrading bacteria were screened by straw powder plate,filter paper hole method and wheat straw degradation rate.The extracellular cellulase activities of the strains were determined to study the degradation ability of the straw cellulose.The results showed that among the four strains screened,the degradation rate of the strains z-5 was the highest,it was 47%,and strains 4-1?3-1 and 2-2 were 45%?32% and 31%,respectively.The filter paper degradation test results were similar to the straw degradation test results.Four strains all had endo-1,4-?-D-glucanase,exo-1,4-?-D-glucanase and ?-glucosidase,but their trends were different.The three enzyme activities of strain z-5 and strain 4-1 showed better synergy,and that of strain 2-2 and strain 3-1 were less synergistic.Through the straw powder plate test,straw degradation rate determination and filter paper hole method,the target strain can be obtained more accurately and quickly;The cellulase plays a leading role in straw degradation.2?To obtain drought-tolerant straw-degrading bacteria,this experiment used medium containing different concentrations of PEG6000 to domesticate the strains,and the cellulase activities of the strains and the degradation rate of wheat straw under different humidity were determined before and after acclimation.The results showed that,under the stress of high concentration of PEG6000,the biomass of strains P3-1 and Pz-5 was significantly higher than that of strain 3-1 and strain z-5;the endoglucanase and exoglucanase of strain P3-1 were higher than strain 3-1,but the ?-glucanase was only 1/5 of strain 3-1;the three enzyme activities of strain Pz-5 were lower than strain z-5,and the peak appeared later.Under different humidities,the degradation effects of strains P3-1 and Pz-5 on straw were significantly better than those before domestication.This indicates that domestication of the strain with PEG6000 can improve the drought tolerance of the strain.The energy of producing enzyme may be promoted with the presence of PEG6000,but the effect of PEG6000 on cellulase activity is related to the type of enzyme and strain and is non-directional.The wheat straw stalk degradation effect of domesticated strains was better than that of the original strains.3?In this experiment,the different concentrations of NaCl was used to acclimate the strains,and investigated the growth ability of the strain,the ability to produce enzymes and the ability to degrade wheat straw under different humidity conditions.The results showed that under the stress of high concentration of NaCl,the biomass of strains of G3-1 and Gz-5 were significantly better than those of strain 3-1 and strain z-5;The endoglucanase and exoglucanase activities of strains G3-1 and Gz-5 were lower than strains 3-1 and z-5,but ?-glucosidase was significantly higher than strains 3-1 and z-5;the degradation rate of wheat straw of the domesticated strains were higher than the original strains under low humidity.This indicates that the acclimation of strains with high concentration of NaCl can improve the drought tolerance of the strains,but there are certain restrictions on the ability of some strains to produce enzymes.The degradation effect of wheat straw after domestication is better than that of the original strains.4?The strains after acclimation and before acclimation in this experiment were separately prepared into powdery fungi and mixed evenly,and the straw degradation effect was tested in a pot experiment.The results showed that the straw was decomposed best under normal irrigation and application of microbial agents.On the 50 th day,the weight loss rate of the straw can reach 53%,which was 16.2% higher than the control group without the application of the microbial agent.After the irrigation amount was halved,the weight loss rate of the straw in the potting agent was still 48% on the 50 th day,and the weight loss rate of the straw was only 30.6% in the blank control without the application of the microbial agent.This indicates that the microbial agent in this experiment can improve the decomposing effect of straw in the field of burying and returning to the field in a relatively dry environment.