Characterization, gene cloning, and expression of a novel xylanase XYNB from Streptomyces olivaceoviridis A1

A novel xylanase XYNB from Streptomyces olivaceoviridis A1 was purified to electrophoretic homogeneity with the specific activity of 2869.78 U/mg, by ammonium sulfate precipitation, anion exchange and gel filtration chromatography. The purified XYNB was further characterized. The optimal pH and temperature for XYNB activity are 5.2 and 60 °C, respectively. Metal cations, EDTA and SDS had no or little effect on enzyme activity. The gene xynB coding mature protein of XYNB was cloned by degenerated PCR, which consisted of 576 bp and encoded 191 amino acid residues. The putative molecular weight of XYNB is about 20.8 kD. The xynB was expressed actively in both Escherichia coli and Pichia pastoris. In a 3 L fermentor, the expressed xylanase protein was accumulated up to 7 mg/mL in recombinant P. pastoris, and the xylanase activity exceeded 15,000 IU/mL. XYNB can be potentially utilized in fish feed industry.