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A Thermostable Extracellular α-amylase from Bacillus licheniformis Isolated from Cassava Steep Water

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Author(s): M.M. Adeyanju | F.K. Agboola | B.O. Omafuvbe | O.H. Oyefuga | O.O. Adebawo

Journal: Biotechnology
ISSN 1682-296X

Volume: 6;
Issue: 4;
Start page: 473;
Date: 2007;
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Keywords: α-amylase | cassava | starch | Bacillus licheniformis

ABSTRACT
The isolation and taxonomic characterization of Bacillus licheniformis isolated from cassava steep water and the purification and characterization of its extracellular amylase (α-1, 4-glucano-4-glucanohydrolase, EC 3. 2. 1. 1) were carried out in this study for the potential use of the enzyme for cassava starch hydrolysis for industrial purposes. The enzyme was purified by ion-exchange chromatography on DEAE-Cellulose and gel filtration on Bio-Gel P100 column. The specific activity of the purified enzyme was approximately 855 units per mg of protein (U mg-1). The enzyme is a large protein with apparent molecular weight determined by gel filtration on Bio-Gel P100 of greater than 100, 000 Daltons. The enzyme obeys sigmoidal kinetics with a kinetic constant (K1) for soluble starch of 1.097 ± 0.027% starch and a Vmax of 44.54 ± 1.79 U min-1. The optimum pH and temperature for enzyme activity were 7.5 and 90°C, respectively. The enzyme was stable for 45 min at 90°C. The enzyme was activated by Cd2+, Co2+, Mg2+ and Ni2+ while Fe3+ and Mn2+ moderately activated the enzyme and Zn2+, Ba2+, EDTA and acetamide were inhibitory. This amylase could be useful for the hydrolysis of soluble starch for the production of maltose.

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