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.
Original language | English (US) |
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Pages (from-to) | 1399-1404 |
Number of pages | 6 |
Journal | Enzyme and Microbial Technology |
Volume | 39 |
Issue number | 7 |
DOIs | |
State | Published - Nov 3 2006 |
Keywords
- Bacillus
- Properties
- Pullulanase
- Purification
- Thermophilic
ASJC Scopus subject areas
- Biotechnology
- Bioengineering
- Biochemistry
- Applied Microbiology and Biotechnology