关键词: Pseudallescheria sp. JSM-2, 碱性木聚糖酶, 基因克隆与表达, 毕赤酵母

Abstract: An alkali-tolerant fungal strain, Pseudallescheria sp. JSM-2, was isolated from the wastewater of a paper mill. By using degenerate PCR and TAIL-PCR techniques, a full-length xylanase gene, xyl11-1, was cloned from the genomic DNA of strain JSM-2. The complete genomic and chromosomal DNA sequences of xyl11-1 consist of 797 bp and 678 bp, respectively. Deduced XYL11-1 contains a putative 18-residue signal peptide at N-terminus and a C-terminal 207-residue polypeptide. Recombinant XYL11-1 produced in Pichia pastoris GS115 was purified and characterized. The optimal pH of XYL11-1 was 6.5, and the enzyme exhibited more than 50% of the maximal activity at pH 4.5~9.0. XYL11-1 was stable at pH 4.5~12.0. The optimal temperature was found to be 50 ℃. XYL11-1 had a specific activity of 2 618 U/mg towards oat spelt xylan, and was strongly resistant to various neutral and alkaline proteases. In addition to hydrolysis of different xylans, XYL11-1 had broad substrate specificity, including various xylans, cellulose and glucan. Moreover, fermentation of XYL11-1 was easily handled. These superior properties of XYL11-1 make it advantageous for applying in the animal and fish feed and kraft pulp industries.

Key words: Pseudallescheria sp. JSM-2, alkaline xylanase, gene cloning and expression, Pichia pastoris