Screening And Identification Of Cellulase-producing Actinomycetes With The Capacity Of High-temperature Tolerance And Optimization Of Its Fermentation Conditions

Cellulose is the organic compounds of the nature,is the largest storage capacity of renewable resources.However,only a small part of natural cellulosic resources are effectively utilized, whereas the vast majority have been wasted and cause the environmental pollution,to some extent. Therefore,the effective degradation of cellulose resources is a worldwide problem,the solution of which would be to promote the sustainable development of utilization of cellulose resources.In this study,the cellulose-congo red plates were at first used to observe whether the microbial strains could produce transparent circles around the colonies. As a result,eight strains were found to show the ability to degrade cellulose. And then the above strains were re-screened in high temperature conditions to obtain the strains with the high carboxymethyl cellulase activity, filter paper activity and β-glucosidase activity of. One strain,designated B-172-A-5, was eventually obtained. This strain showed the highest enzymatic activities at 50 ℃, the carboxymethyl cellulose activity,of filter paper activity and of β-glucosidase activity of which were 213.49 U/ml,170 U/ml and 211 U/ml,respectively.Based on 16 S r DNA sequence analysis and physiological and biochemical characterization,strain B-172-A-5 belongs to the genus Streptomyces, and its species name was therefore designated Streptomyces violaceorubidus, based on the 16 S r DNA sequence homology analysis.The fermentation conditions for Streptomyces violaceorubidus were optimized. Single-factor tests for solid state fermentation substrates were screened on the basis of the screening results, then the optimum fermentation conditions were preliminarily determined through the experimental analysis of an orthogonal design. The results showed that the optimum solid state fermentation strain matrix(rice flour) contained 60 mg/g corn straw and 30 mg/g millet flour,and the optimum fermentation conditions were the following: the inoculation size of 0.4 mL/g,the initial moisture content of 400 mg/g,and incubation time of 192 h. Sporulation rates were determined to be up to 1.2×108 CFU / mL.The temperature is 50℃under the conditions determined carboxymethyl cellulose activity was 289 U / ml, the filter paper activity was 281 U / ml,β- glucosidase activity was 271 U / ml.In this study, one cellulase-producing actinomycete strain with the capacity of high-temperature tolerance,designated B-172-A-5,was obtained and its fermentation conditions were preliminarily optimized. However,this study focused mainly on the analysis of the effect of optimum cellulase-producing temperature on the enzymatic activities under high temperatures. The enzymatic properties of the cellulase produced by strain B-172-A-5 needs to be further investigated. Also, due to the limited phylogenetic analysis based on the 16 S r DNA gene sequences,the taxonomy position of strain B-172-A-5 needs to be carried out by using the polyphasic taxonomy.