Gene cloning and characterization of a thermostable organic-tolerant α-amylase from Bacillus subtilis DR8806

The gene encoding an extracellular alpha-amylase from Bacillus subtilis DR8806 was cloned into pET28a(+) vector and expressed in Escherichia coli BL21 (DE3). The recombinant enzyme with molecular mass of 76 kDa exhibited optimal activity at pH 5.0 and 70 degrees C with high stability in pH and temperature ranges of 4.0-9.0 and 45-75 degrees C. The enzyme showed a half-life of 125 min at 70 degrees C. The alpha-amylase activity enhanced in the presence of Na+, K+, and Ca2+ ions, while Zn2+, Pb2+, and Hg2+ ions inhibited the activity. The recombinant alpha-amylase exhibited high stability towards ioninc detergents sodium dodecyl sulfate (SDS) and cetyl trimethylammonium bromide (CTAB). Organic solvents in reaction media increased the or-amylase activity. TLC analysis showed that maltoriose and maltose were the major end products of enzymatic starch hydrolysis. Presenting various properties of recombinant or-amylase makes it well suited as a potential candidate for industrial usages. (C) 2014 Elsevier B.V. All rights reserved.