The Xylanase Properties and the Xylanase Gene of Streptomyces sp. zxy19
链霉菌zxy19木聚糖酶酶学性质及酶基因克隆

A mangrove actinomycetes strain zxy19 that has shown strong xylanase activity was selected by plate screening. Sequencing analysis and Blast search of the 16S rDNA gene of the strain revealed that the highest identity in the database was 96% against Streptomyces sampsonii. Characterization of the xylanase enzymatic properties of zxy19 has shown that the optimal pH was 7 and the optimal temperature was 60°C. Degenerate primers were designed according to the conservative domains of actinomycetal xylanase to amplify the partial xylanase gene. The complete enzyme gene xyl696 was obtained by inverse PCR subsequently and confirmed by DNA sequence analysis. Blast search of the translated amino acid sequence suggested that the enzyme belongs to the glycosyl hydrolases family 11 with the highest similarity as 79% against the xylanase B produced by Streptomyces lividans. The xylanase gene was cloned into the expression vector to construct pET-28a-xyl696 and introduced into E. coli BL21(DE3). After IPTG inducing, the over expressed recombinant xylanase was purified by Ni2+-NTA affinity chromatography and proved to have catalytic activity.