High-level expression of extracellular secretion of a beta-xylosidase gene from Paecilomyces thermophila in Escherichia coli

A novel beta-xylosidase gene (designated as PtXy143) from thermophilic fungus Paecilomyces thermophila was cloned and extracellularly expressed in Escherichia coli. PtXy143 belonging to glycoside hydrolase (GH) family 43 has an open reading frame of 1017 bp, encoding 338 amino acids without a predicted signal peptide. No introns were found by comparison of the PtXy143 genomic DNA and cDNA sequences. The recombinant beta-xylosidase (PtXy143) was secreted into the culture medium in E. coli with a yield of 98.0 U mL(-1) in shake-flask cultures. PtXy143 was purified 1.2-fold to homogeneity with a recovery yield of 61.5% from the cell-free culture supernatant. It appeared as a single protein band on SDS-PAGE with a molecular mass of approx 52.3 kDa. The enzyme exhibited an optimal activity at 55 degrees C and pH 7.0, respectively. This is the first report on the cloning and expression of a CH family 43 beta-xylosidase gene from thermophilic fungi. (C) 2010 Elsevier Ltd. All rights reserved.