Screening Of Stalk Cellulose-degrading Microorganisms And Construction Of A Microbial Community With High Capacity

In order to resolve the problem that caused by the straw waste and make full use of thecrop straw, the cellulose-degrading microbial community was expected to be obtained and itseffects on straw degradation were studied.Screening of microbial community:Cellulose congo-red culture medium was used forscreening soil samples, and then CMC，FPA，C₁andβ-Gase were used for re-screening,bywhich the strains with high capacity were obtained. The strains were mixed cultured, and amicrobial community with high capacity was screened.Study of factors affecting microbial community fermetation: We studied various factorsaffecting microbial community liquid-state fermetation including different time, temperature,pH values, C resources and N resources in fixed time every day.Determination of ye-9/er-72/se-93: We studied the ability of corn straw degradation ofye-9/er-72/se-93 by using weight loss method and SEM pictures.Strains identification: The analysis of morphology and 16S rRNA gene sequences wereperformed to identify the strains of ye-9, er-72 and se-93.The results were as follows:Screening of microbial community: Five strains that could decompose cellulose betterwere obtained from soil samples. Then they were cultured by mixed fermentation. Thecombination of ye-9/er-72/se-93 enhanced cellulase activities containing CMC，FPA，C₁andβ-Gase to some degree, and the enzyme activity of CMC，FPA，C₁andβ-Gase was3.18,1.67,1.08 and 1.12 U / mL.Study of factors affecting ye-9/er-72/se-93 fermetation: The results showed that theoptimum time for enzyme produced by ye-9/er-72/se-93 was the forth day, the optimumtemperature was 40℃, the optimum pH value was 7.5, the optimum C resource was cornstraw and the optimum N resource was NaNO3.Determination of ye-9/er-72/se-93: The cellulose, hemicellulose and lignin contents werereduced by 24.07%, 28.31% and 18.39% respectively in 8 days.The SEM pictures indicatedthat corn straw was degraded better by ye-9/er-72/se-93 than single strain.Strains identification:They were classified as Streptomyces carpaticus，Streptomycesgriseorubens and Streptomyces rochei respectively by the analysis of their morphology and16S rRNA gene sequences.The study found that the enzyme activity of the microbial community was higher thanthat of single bacteria. The study could provide a theorotical basis on mixed fermentationbetween microorganisms.