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

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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 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 languageEnglish (US)
Pages (from-to)1399-1404
Number of pages6
JournalEnzyme and Microbial Technology
Issue number7
StatePublished - Nov 3 2006


  • Bacillus
  • Properties
  • Pullulanase
  • Purification
  • Thermophilic

ASJC Scopus subject areas

  • Biotechnology
  • Bioengineering
  • Biochemistry
  • Applied Microbiology and Biotechnology


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