一株纤维素降解菌的筛选、鉴定及对饲料粗纤维降解效果的研究

Screening and identifying of a cellulose-degrading bacteria and its study on degradation rate of crude fiber in feed

通过筛选高活性纤维素酶产生菌,为微生物纤维素酶制剂的开发提供理论依据。采用刚果红染色法从绵羊粪便中分离筛选纤维素降解菌,用DNS法测定酶活力,根据酶活力复筛后,分离得到一株能够产生高活力纤维素酶和β-葡萄糖苷酶的目的菌B5。通过形态学观察和16S rDNA序列测定,对B5菌株进行种属鉴定;应用B5菌株对四种纤维性饲料进行消化降解实验,探究菌株B5降解饲料粗纤维的特性。形态学观察确定B5菌落符合放线菌的特征;分子学鉴定其16S rDNA序列全长1 585 bp,在进化关系上与链霉菌属(Streptomyces sp.)聚成一簇,同源性高达99%。鉴定B5菌株属于链霉菌属成员。B5菌株对饲料粗纤维降解效率与酶活力显著相关,对饲料粗纤维降解效率与饲料中纤维素含量相关性不明显。

The screening of cellulase producing bacteria provides theoretical basis for the development of cellulase preparation.Cellulose degrading bac⁃teria were isolated and screened from sheep fe⁃ces by Congo-red staining,and enzyme activity was measured by DNS method.After rescreening according to enzyme activity,a strain of target bacterium B5 which could produce high-activity cellulase and beta-glucosidase was isolated.Through morphological observation and 16S rD⁃NA sequencing,the species and genus of the rescreened strain were identified.Four kinds of feed crude fibers were digested and degraded by B5 strain to investigate the characteristics of the degraded feed crude fibers.Morphological observation confirmed that B5 colonies were consistent with the characteristics of actinomycetes.Molecular identifi⁃cation of its 16S rDNA sequence length of 1585 bp,in the evolutionary relationship with the genus Streptomyces sp.cluster,homology up to 99%.The strain B5 belongs to Streptomyces sp..The B5 strain had significant correlation with the degradation efficiency and enzyme activity of crude fiber,but not with the content of cellulose in feed.