Purification and Characterization of Beta-Amylase of Bacillus subtilis Isolated from Kolanut Weevil

Abstract

An extracellular beta amylase was induced in cultures of Bacillus subtilis isolated from the kolanut weevil, Balanogastris kolae grown in liquid medium that contained kolanut starch as sole carbon source. The enzyme was partially purified 1.28-fold by acid treatment with ice cold 1.0N HCl and 6.4-fold by gel filtration with Sephadex G-150. The beta amylase had a molecular weight of 39.4 kDa .The enzyme had its optimal activity at pH 5.0 and exhibited maximal activity at temperature of 50^oC. The activity of the enzyme was enhanced by Na⁺, Ca²⁺  and ethylene diaminetetraacetic acid (EDTA), while Hg²⁺ ,Mg²⁺ and  Fe²⁺ acted as inhibitors of its activity. The beta amylase had an apparent Michaelis constant K_m of 5.0 mg/ml and maximum velocity (V_max) of 50 U/mg proteins.