A novel family 9 beta-1,3(4)-glucanase from thermoacidophilic Alicyclobacillus sp. A4 with potential applications in the brewing industry.

An endo-beta-1,3(4)-glucanase gene, Agl9A, was cloned from Alicyclobacillus sp. A4 and expressed in Pichia pastoris. Its deduced amino acid sequence shared the highest identity (48%) with an endo-beta-1,4-glucansae from Alicyclobacillus acidocaldarius that belongs to family 9 of the glycoside hydrolases. The purified recombinant Agl9A exhibited relatively wide substrate specificity, including lichenan (109%), barley beta-glucan (100%), CMC-Na (15.02%), and laminarin (6.19%). The optimal conditions for Agl9A activity were pH 5.8 and 55 degrees C. The enzyme was stable over a broad pH range (>60% activity retained after 1-h incubation at pH 3.8-11.2) and at 60 degrees C (>70% activity retained after 1-h incubation). Agl9A was highly resistant to various neutral proteases (e.g., trypsin, alpha-chymotrypsin, and collagenase) and Neutrase 0.8L (Novozymes), a protease widely added to the mash. Under simulated mashing conditions, addition of Agl9A (20 U/ml) or a commercial xylanase (200 U/ml) reduced the filtration rate (26.71% and 20.21%, respectively) and viscosity (6.12% and 4.78%, respectively); furthermore, combined use of Agl9A (10 U/ml) and the xylanase (100 U/ml) even more effectively reduced the filtration rate (31.73%) and viscosity (8.79%). These characteristics indicate that Agl9A is a good candidate to improve glucan degradation in the malting and brewing industry.