An acidophilic and Ca2?-independent amylase was purified from a newly isolated Bacillus sp. DR90 by ion-exchange chromatography, and exhibited a molecular weight of 68.9 kDa by SDS-PAGE. The optimum pH and temperature of the enzyme were found to be 4.0 and 45 C, respectively. The enzyme activity was increased by Ba2?, Fe2? and Mg2?, and decreased by Hg2? and Zn2?, while it was not affected by Na?, K?, phenylmethylsulfonyl fluoride and b-mercaptoethanol. Ca2? and EDTA did not have significant effect on the enzyme activity and thermal stability. The values of Km and Vmax for starch as substrate were 4.5 ± 0.13 mg/ml and 307 ± 12 lM/min/mg, respectively. N,N-dialkylimidazolium-based ionic liquids such as 1-hexyl-3-methylimidazolium bromide [HMIM][Br] have inhibitory effect on the enzyme activity. Thin layer chromatography analyses displayed that maltose and glucose are the main products of the enzyme reaction on starch. Regarding the features of the enzyme, it may be utilized as a novel candidate for industrial applications.

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