一株纤维素酶产生菌SWU6菌株的筛选鉴定

Screening and Identification of a Cellulase-Producing Bacterium Strain SWU6

为寻找高效纤维素降解菌,用于蚕沙及桑树废弃枝条等的加工处理,本研究以羧甲基纤维素钠(CMC-Na)为唯一碳源,从西南大学校园土壤中分离纤维素降解菌。结合测定菌株在羧甲基纤维素钠平板上形成水解圈直径与其菌落直径的比值,及胞外酶活测定法(DNS法)筛选获得一株纤维素酶高产菌株SWU6。该菌株24h发酵液上清液经DNS法检测纤维素酶活力达到136.24U/mL。菌种鉴定结果表明SWU6菌株为革兰氏阳性芽孢杆菌;过氧化氢酶、硝酸盐还原呈阳性;能水解淀粉、液化明胶。基于16SrDNA的系统发育分析结果表明SWU6菌株与登录号为NR 116240的甲基营养型芽孢杆菌(Bacillus methylotrophicus)处于进化树的同一最小分支。综合菌体及菌落形态特征、生理生化实验结果以及基于16SrDNA的系统发育分析,将SWU6菌株鉴定为甲基营养型芽孢杆菌(Bacillus methylotrophicus)。

In order to screen out efficient cellulose-degrading bacteria which can be used to process silkworm excrement and waste mulberry branches,cellulose-producing strains were isolated on the substrate with sodium carboxymethyl cellulose（CMC-Na）as the sole carbon source from the campus soil of Southwest University.A highly efficient cellulose-producing strain,SWU6,was obtained,using the methods of CMC-Nahydrolysis circle assay and extracellular enzyme activity assay（DNS）.Determination of the fermentation supernatant of the strain with DNS method when it was cultivated 24 hshowed that the cellulase activity of SWU6 was up to 136.24U/ml.Strain identification results showed that SWU6 was gram positive,catalase positive and nitrate reduction positive,and could hydrolyze starch and liquefy gelatine.The phylogenetic analysis based on 16 SrDNA sequence showed that SWU6 was in the same minimal clade with Bacillus methylotrophicus（accession number：NR116240）.In conclusion,SWU6 was identified to be a strain of Bacillus methylotrophicus according to its morphological characteristics,physiological and biochemistry assays and 16SrDNA-based phylogenetic analysis.