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Improved high thermal stability of pullulanase from a newly isolated thermophilic Bacillus sp. AN-7

Paper ID Volume ID Publish Year Pages File Format Full-Text
18460 42724 2006 6 PDF Available
Title
Improved high thermal stability of pullulanase from a newly isolated thermophilic Bacillus sp. AN-7
Abstract

A thermophilic Bacillus sp. strain AN-7, isolated from a soil in India, produced an extracellular pullulanase upon growth on starch–peptone medium. The enzyme was purified to homogeneity by ammonium sulfate precipitation, anion exchange and gel filtration chromatography. The optimum temperature and pH for activity was 90 °C and 6.0. With half-life time longer than one day at 80 °C the enzyme proves to be thermostable in the pH range 4.5–7.0. The pullulanase from Bacillus strain lost activity rapidly when incubated at temperature higher than 105 °C or at pH lower than 4.5. Pullulanase was completely inhibited by the Hg2+ ions. Ca2+, dithiothreitol, and Mn2+ stimulated the pullulanase activity. Kinetic experiments at 80 °C and pH 6.0 gave Vmax and Km values of 154 U mg−1 and 1.3 mg ml−1. The products of pullulan were maltotriose and maltose. This proved that the purified pullulanase (pullulan-6-glucanohydrolase, EC 3.2.1.41) from Bacillus sp. AN-7 is classified under pullulanase type I. To our knowledge, this Bacillus pullulanase is the most highly thermostable type I pullulanase known to date.

Keywords
Pullulanase; Bacillus; Thermophilic; Purification; Properties
First Page Preview
Improved high thermal stability of pullulanase from a newly isolated thermophilic Bacillus sp. AN-7
Publisher
Database: Elsevier - ScienceDirect
Journal: Enzyme and Microbial Technology - Volume 39, Issue 7, 3 November 2006, Pages 1399–1404
Authors
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Subjects
Physical Sciences and Engineering Chemical Engineering Bioengineering