| Crop straw returning to the field is the main method for the treatment of agricultural wastes.It can not only reduce the atmospheric pollution caused by straw in-situ burning,but also improve the utilization of straw,raise the soil structure,increase the soil fertility and water holding capacity.However,microbial metabolic activities were inhibited especially by the long-term low temperature in the fall and the winter of the northern China,which would slow down the degradation of the treated straw in the soil and generate many adverse effects on the agricultural cultivation and production.It is necessary to screen highly efficient cellulose decomposition microbes under low temperature,which can improve the speed of decomposition after crop straw returning to the field.In this experiment,soil sample was a source of strains,cryogenic cellulose environment was used to domesticate and cultivate strains,which eliminated strains that do not have the ability to degrade cellulose and the survived strains adapted to the current environment were reserved.Nineteen strains of cellulose degradation were obtained through the further separation and purification.The strains were preliminary screened by disintegration of the filter paper strips and Congo red staining,and 13 strains having cellulose degradation ability were obtained.Under the culture condition of 10°C,the carboxymethyl cellulose activity(CMCase),?-glucosidase activity(?-Gase)and filter paper enzyme activity(FPA)of 13 strains were determined.Finally,three cellulose-degrading strains with higher cellulase activity were isolated from the soil in a low temperature environment of 10°C.ZS-7 was Cladosporium sp,ZS-8 was Alternaria porri and ZS-10 was Trichoderma harzianum by molecular identification analysis.The three strains were subjected to an antagonistic experiment in order to construct a cellulose-degrading composite strains system in low temperature environment.By observing and recording the growth of the strains,this experiment found that ZS-7,ZS-8 and ZS-10 were not antagonized one another;therefore,they can be mixed and cultured for further experiments and marked as ZS-M.In a low temperature of 15°C,the dominant strains and cellulose-degrading composite strains were respectively subjected to static fermentation tests of corn straw and filter paper static fermentation tests.The carboxymethyl cellulase activity,?-glucosidase activity and filter paper enzyme activity of the fermentation broth were measured,and each test group expressed a higher enzyme-producing ability.After 30 days' static cultivation,the corn straw degradation of ZS-7,ZS-8,ZS-10 and ZS-M was 45.98%,47.96%,34.22% and 33.56%,respectively.The filter paper decreased by 41.08%,47.55%,29.51% and 30.88% under the same conditions.The pH of the fermentation broth during corn straw degradation was measured,and the pH values of ZS-7,ZS-10 and ZS-M were particularly stable.During the whole fermentation process,the pH of ZS-7,ZS-10 and ZS-M changed from 7.08 to 7.77 in a neutral pH niche,indicating that there were certain degrees of self-discipline and stability.In order to close to the actual natural degradation environment and further investigate the practical application of ZS-7,ZS-8,ZS-10 and ZS-M,a simulation experiment of corn straw returning was carried out.After 30 d natural degradation under low temperature environment of outdoor with the combined action of soil microorganisms,the corn straw degradation of ZS-7,ZS-8,ZS-10 and ZS-M was 30.64%,30.53%,27.79% and 26.06%,respectively;which had an increase of nearly 20% compared with the blank test. |
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