Gene cloning and expression of a new acidic family 7 endo-β-1,3-1,4-glucanase from the acidophilic fungus Bispora sp. MEY-1

Abstract

Most reported microbial beta-1,3-1,4-glucanases belong to the glycoside hydrolase family 16. Here, we report a new acidic family 7 endo-beta-1,3-1,4-glucanase (Bgl7A) from the acidophilic fungus Bispora sp. MEY-1. The cDNA of Bgl7A was isolated and over-expressed in Pichia pastoris, with a yield of about 1,000 U ml(-1) in a 3.7-l fermentor. The purified recombinant Bgl7A had three activity peaks at pH 1.5, 3.5, and 5.0 (maximum), respectively, and a temperature optimum at 60 degrees C. The enzyme was stable at pH 1.0-8.0 and highly resistant to both pepsin and trypsin. Belonging to the group of non-specific endoglucanase, Bgl7A can hydrolyze not only beta-glucan and cellulose but also laminarin and oat spelt xylan. The specific activity of Bgl7A against barley beta-glucan and lichenan (4,040 and 2,740 U mg(-1)) was higher than toward carboxymethyl cellulose sodium (395 U mg(-1)), which was different from other family 7 endo-beta-glucanases.