Enzymic properties of an alkaline chelator-resistant α-amylase from an alkaliphilic Bacillus sp. isolate L1711

An alkaliphilic amylase producing bacterium, Bacillus sp. strain L1711, was selected from 13 soda lakes isolates. When grown at pH 10.5 and 37 °C, strain L1711 produced multiple forms of amylases in the culture broth. One of these, BAA, was purified from the culture supernatant by QAE column chromatography and preparative native gel electrophoresis. The molecular weight of BAA was determined to be 51 kDa by SDS gel electrophoresis. The pH optima for activity below and above 40 °C were 9.5–10.0 and 7.0–7.5, respectively. BAA was stable in the pH range 6–11 and was completely inactivated at 55 °C. Thermostability was not increased in the presence of Ca2+. The enzyme was strongly inhibited by Ca2+, Zn2+, Mg2+, Mn2+, Ba2+ and Cu2+, whereas the presence of Na+, Co2+ and EDTA (10 mM) enhanced enzymic activity. The Km and specific activity of BAA on soluble starch were 1.9 mg/ml and 18.5 U/mg, respectively.