Purification and characterization of extracellular α-amylase from a thermophilic Anoxybacillus thermarum A4 strain

α-Amylase from Anoxybacillus thermarum A4 was purified using ammonium sulphate precipitation and Sephadex G-100 gel filtration chromatography, with 29.8-fold purification and 74.6% yield. A4 amylase showed best performance for soluble potato starch hydrolysis at 70 °C and pH 5.5-10.5. A4 amylase was extremely stable at +4 °C, and the enzyme retained over 65% of its original α-amylase activity at 70 °C and 43% at 90 °C. The enzyme’s Km values for soluble starch, amylopectin and amylose substrates were obtained as 0.9, 1.3 and 0.5 mg/mL, respectively. EDTA, Hg 2+ , B4O7 2, OH , CN , and urea exhibited different inhibition effects; their IC50 values were identified as 8.0, 5.75, 16.5, 15.2, 8.2 and 10.9 mM, respectively. A4 amylase exhibited extreme stability toward some surfactants and perfect match for a wide variety of commercial solid and liquid detergents at 55 °C. So, it may be considered to be potential applications for detergent and other industrial uses.