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 α-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.