A pH-stable, detergent and chelator resistant type I pullulanase from Bacillus pseudofirmus 703 with high catalytic efficiency

Pullulanase with high catalytic efficiency has attracted great attention from both the academic and industrial communities for its wide application in cold starch hydrolysis. A novel pullulanase gene pul703 was cloned from a mesophilic bacteria Bacillus pseudofirmus 703. Pu1703 was characterized to be a type I pullulanase with maximal activity at 45 degrees C and good low-temperature stability, more than 70% of activity was detected after incubation at 25-35 degrees C for 72 h. Pu1703 obtained the maximal activity around pH 7.0-8.0, and was highly active and stable over a wide pH range of 5.5-9.5, more than 80% of activity was retained after 12 h incubation in these pHs. Pu1703 was EDTA-resistant and detergent-tolerant, with a relative activity of 100, 99, and 114.8% at the presence of 10 mM EDTA, 10% of Triton X-100 and Tween 20, respectively. Pu1703 can efficiently hydrolyze pullulan with a specific activity of 270 U/mg, which was higher than all reported type I pullulanases. In addition, Pu1703 can act synergistically with alpha-amylase BLA to efficiently hydrolyze amylopectin. These results suggested that Pu1703 was a good candidate for cold starch hydrolysis. (C) 2017 Elsevier B.V. All rights reserved.