Purification and characterization of maltooligosaccharide-forming amylase from Bacillus circulans GRS 313

A maltooligosaccharide-forming amylase that hydrolyzes starch into maltotriose and maltopentaose was found in the culture filtrate of a strain of Bacillus circulans GRS 313 isolated from local soil. The enzyme was purified by organic solvent fractionation, Sephadex G-100 gel filtration and CM-Sephadex column chromatography. Optimum pH and temperature of amylase were evaluated using response surface methodology (RSM) and were found to be 48 degrees C and 4.9, respectively. The enzyme was stable up to 60 degrees C and its pH stability was in the range of 5.0-8.0. The Km and Vmax of the amylase with starch were 11.66 mg/ml and 68.97 U, respectively, and the energy of activation, Ea, was 7.52 kcal/mol. Dextrin inhibited the enzyme competitively, with a Ki of 6.1 mg/ml, and glucose caused noncompetitive inhibition with a Ki of 9.5 mg/ml. The enzyme was inhibited by Hg2+, Mn2+, Fe3+ and Cu2+ and enhanced by Co2+ and Mg2+. EDTA reversed the inhibitory effect of the metals. Paper chromatographic and high-performance liquid chromatography analysis of the products of the amylolytic reaction showed the presence of maltotriose, maltotetraose, maltopentaose, maltose and glucose in the starch hydrolysate.