High-level production and characterization of a novel β-1,3-1,4-glucanase from Aspergillus awamori and its potential application in the brewing industry

A novel beta-1,3-1,4-glucanase gene (AaBglu12A) from Aspergillus awamori was extracellularly expressed in Pichia pastoris. AaBglu12A showed amino acid identity of 96 % with a glycoside hydrolase family 12 cellulase from A. kawachii and 48 % with a beta-1,3-1,4-glucanase from Magnaporthe oryzae. The highest beta-1,3-1,4-glucanase activity of 159,500 +/- 500 U/mL with protein concentration of 31.7 +/- 0.3 g/L was achieved in a 5-L fermentor. AaBglu12A was purified until homogeneous with recovery yield of 92 %. Its maximal activity was found at 55 degrees C and pH 5.0. The enzyme was stable up to 60 degrees C and within the pH range of 2.0-9.0. It also demonstrated strict substrate specificity towards oat- and barley-glucans as well as lichenan. The K-m values for oat-, barley-glucans, and lichenan were 2.82, 3.51, and 2.53 mg/mL, respectively. The V-max values for oat-, barley-glucans, and lichenan were 12,068, 10,790, and 7236 mu mol/min.mg, respectively. AaBglu12A hydrolyzed oat- and barley-figlucans to produce tetra- and tri-saccharides. However, lichenan was hydrolyzed to yield trisaccharides as the main end product. The addition of AaBglu12A to the mashing process substantially decreased filtration time by 34.5 % and viscosity by 9.6 %. Therefore, the high-level production of AaBglu12A might be a promising strategy for the brewing industry owing to its favorable properties.