Abstract:
beta]-Xylosidase gene of Streptomyces sp. CH7 in the recombinant plasmid pCH7-1 has comparable expression ability either in E. coli strains DH5[alpha] without induction or JM109 induced with 0.2 M IPTG. Furthermore, its expression ability was increased by xylan but repressed by glucose and xylose when used as a carbon source for cultivation. The optimal cultivation time giving maximum enzyme specific activity was 15 h. Purification of [beta]-xylosidase from the recombinant E. coli by column chromatography on DEAE-Biogel A and Sephadex G-200 gave similar purification patterns to that of the enzyme from the wild type. The purified enzyme had pH and temperature optimum including its stability to pH and temperature properties similar to that of the wild type. It had molecular weight of 178,000 Da estimated by gel filtration and consisted of 2 identical subunits with molecular weight of 75,000 Da. From the nucleotide sequence analysis of the DNA insert in the recombinant plasmid pCH7-1, it showed one complete open reading frame from nucleotide numbers 552 to 2927 encoding 792 amino acids with calculated molecular weight of 83,386 Da.