Molecular cloning and biochemical characterization of a thermoacidophilic, organic-solvent tolerant α-amylase from a Bacillus strain in Escherichia coli

Abstract The α-amylase gene from Bacillus sp. DR90 was isolated, inserted into pET28a(+) vector and subsequently expressed in Escherichia coli BL21 (DE3) using 1 mM IPTG as an inducer. Recombinant enzyme containing N-terminal His-tag was sufficiently purified via nickel metal affinity chromatography with purification factor of 6.8-fold and specific activity of 4091 U/mg. The molecular mass of α-amylase was estimated to be about 76 kDa by SDS-PAGE. The recombinant enzyme was active in wide ranges of pH and temperature, exhibiting an optimal activity at pH 4 and 75 °C with T 1/2 of 125 min. Amylase activity did not enhance in the presence of calcium ions. Apart from good stability toward SDS, urea, and EDTA, the purified enzyme showed high compatibility with various solid and liquid detergents. Furthermore, results indicated the stability and stimulation of enzyme in the presence of different organic solvents. Following the incubation of amylase with imidazolium-based ionic liquids, maximum remaining activity was observed in [BMIm][Cl]-containing solution. Overall, presenting outstanding properties including high thermostability, Ca 2+ -independency, broad pH and temperature profiles, organic-solvent tolerance as well as excellent stability and compatibility with detergents, the present recombinant α-amylase will be a suitable candidate in industrial fields, particularly in food and detergent industries.