Screening, Identification Of High Effective Straw Cellulose-degrading Strains And Their Effects On Crop Straw Degradation

In order to promote the decomposition of crop straw and return it to soil rapidly, high-efficient straw lignocellulose- degradating microorganisms were screened and their effects on straw degradation were studied. The results were as follows:1. Two bacterias, one filamentous fungi were Isolated, three microbial communities were obtained. Two bacterias (50P and 42P) were identified as Bacillus subtilis and Bacillus cereus respectively. strain Y5 was identified as Penicillium ochrochloron. three microbial communities were Y2b, Y54B and 36.2. Results of celluase activities under liquid culture conditions showe that all the celluase activities of Y5 were reached the maximum in the fourth day.Both filter paper activity (FPA) and endo-1,4-β-D- glucanase(Cx) of microbial community Y2b were reached the maximum in the second day, and both exo-β-1,4-D-glucanase(C1) andβ-1,4–glucosidase(BG) were reached the maximum in the third day. FPA and Cx of Y54B reached the maximum in the second day, C1 and BG were both reached the maximum in the third day. C1 and BG of 36 performed more significantly, which reached the maximum in the fourth day. FPA and Cx showed relatively low, which reached the maximum in the fourth and fifth day respectively.During the stage of optimun enzymes production, the optimum pH value for Y5 and Y2b was 6, the pH value was 5 for 36 and AS3.3711 and 6.5 for Y54B. The optimum temperature for enzyme produced by Y5, Y2b, Y54B and 36 was 35℃, 35℃, 40℃and 25℃respectively. The opimum N resource for all microbes were nitrate, and the quantities was 1.5%, 1%, 1.5% and 1.5%. Enzyme activities of 36 and AS3.3711 were the highest when corn straw was used as C resources but wheat straw was berre for other strains.3. The cellulose, hemicellulose and lignin contents of wheat staw with strain Y5 were reduced by 43.5%, 49.7% and 9.3% respectively in 10 days. The content of hemicellulose and cellulose was reduced by 45.9% and 40.2% respectively with Y2b. The content of hemicellulose of wheat atraw with Y54B and 36 were reduced by 11.2% and 10.7% respectively, and cellulose was reduced by 28.7% and 32.6% respectively. Microbial communities Y2b, Y54B and 36 degraded lignin averaged 23.6%, 22.2% and 25.5%, respectively.4. In soil pot experiment, the content of soil organic matter increased about 2.9% with the application of Y2b and Y5. After the 30d's experiment, the hemicellulose, cellulose and lignin content of straw in different treatments , the treatment TM (with Y5) decreased by 4.6%, 14% and 6%. lignin degradation rate of straw applied with Y2b significantly reached 19%.5. The results of DGGE-PCR analysis showed that the community Y2b had better colonization ability. Application of microbial community Y2b with crop straw increased soil microbial biodiversity. A part of dominant bacterias and fungus of Y2b were detected by gel extracting, DNA cloning and sequencing, and most of them were uncultured strains.