characterization of an a-amylase with broad temperature activity from an acid-neutralizing bacillus cereus strain

bacillus sp. guf8, isolated from acidic soil samples of a tea farm was identified as bacillus cereus, based on 16s rdna sequencing and standard bacterial identification methods. following optimization of enzyme production, the resulting α-amylase was purified by acetone precipitation and ion exchange chromatography. consequently, thermostability and kinetic parameters of the purified enzyme were determined. the temperature profile of the enzyme indicated a very broad temperature range (from 10 to 70°c) with 50°c representing the optimum temperature for enzyme activity, which is different from those of the known bacillus a-amylases. this enzyme was optimally active at ph 6.0 and retained 75 and 50% of its maximal activity at ph 8.0 and 9.0, respectively. it was also strongly inhibited by zn2+ and partially inhibited by ni2+ and ethylenediaminetetraacetic acid (edta). the a-amylase enzyme was found to hydrolyze starch forming various maltooligosaccharides, such as maltose (g2) and maltopentaose (g5) as major products.