Purification and Characterization of α-Amylase from Bacillus subtilis Isolated from Cassava Processing Sites

Abstract

This study was designed to purify and characterize of α-amylase from pure strain of Bacillus subtilis. The crude α- amylase was purified by ammonium sulphate precipitation, then loaded on DEAE Sephadex A-50 ion exchange chromatography and gel filtration. The effect of pH, temperature and metal ions were investigated on the purified enzyme. The single protein band on SDS-PAGE suggested that the enzyme was homogenous. Two different activity peaks were observed in ion exchange chromatography designated pool A and pool B with the 8% and 4% yield, 15.93 and 6.44 purification fold and specific activity 2.55 μmol/min/mg and 1.03 μmol/min/mg respectively. The two fractions revealed the same optimum pH 7.0 for the α-amylase activity while the enzyme was relatively stable at pH 4.0 and 7.0 between 20 to 40 minutes and 60 to 80 minutes for pool A and pH 8.0 between 40 and 100 minutes for pool B. At 40°C, optimum temperature was reached, and amylase activity was maintained at 75% and 70% temperature stability between 60 to 80 minutes for pool A and B, less than 20%, the residual activity at 60°C and 70°C was recorded. The incubation of α-amylase with Na+ and Zn2+ ions enhanced/activate the enzyme activity correspondingly, Al3+ and K+ ions exhibited varied degree of inhibition while Ca2+ and Hg2+ ions caused total inhibition on α-amylase activity. The ability of purified α-amylase from Bacillus subtilis under wide range of temperatures and pH suggests its applications in industries and bioremediation of effluent discharge on food processing sites.