Production and properties of the highly efficient raw starch digesting α-amylase from a Bacillus licheniformis ATCC 9945a

▶ A highly efficient, thermostable, raw starch digesting α-amylase was produced. ▶ α-Amylase was purified and its enzymological and molecular properties were studied. ▶ Enzyme has a high hydrolytic affinity towards cereal, tuber and root raw starches. ▶ Very low enzyme doses hydrolyze raw starches below gelatinization temperatures. Highly efficient raw starch digesting α-amylase was produced after 24h of batch fermentation of Bacillus licheniformis ATCC 9945a in laboratory bioreactor at 37°C. The enzyme was purified by gel filtration chromatographies with 6-fold increase of specific activity and 38% recovery and showed a molecular mass of 31kDa by SDS-PAGE. The purified enzyme had an optimum pH of 6.5 and optimum temperature of 90°C. The purified α-amylase in the presence of CaCl2 retained 55% of its activity after 6h of incubation at 70°C. Co2+, Ni2+ and Ca2+ slightly stimulated, while Hg2+ completely inhibited α-amylase activity. Hydrolysis rates of raw triticale, wheat, potato, horseradish and corn starches, at 1% concentration were 63, 60, 59, 52 and 37%, respectively, in a period of 4h. The properties of the purified enzyme proved its high efficacy for digesting diverse raw starches below gelatinization temperature and, hence, its potential commercial value to use as an industrial enzyme.