Purification and characterization of a noble thermostable algal starch liquefying alpha-amylase from Aeribacillus pallidus BTPS-2 isolated from geothermal spring of Nepal

A thermophilic strain, Aeribacillus pallidus BTPS-2 was isolated from Bhurung geothermal spring of Nepal. The 16 s rRNA sequence showed 99.8 % similarity with the type strain Aeribacillus pallidus DSM 3670. The morphological, physiological and biochemical properties were similar to the type strain. Alpha-amylase from A. pallidus BTPS-2 was purified to 19-fold purification by DEAE-Cellulose ion exchange chromatography. The Km value of amylase on starch was 0.51 ± 0.05 mg/mL. The optimum pH and temperature were 7.0 and 70 °C. SDS-PAGE analysis showed a single band at 100 kDa. The half-life of the enzyme at 80 °C was 2.81 h. The enzyme showed an inhibitory effect in the presence of Fe2+, Pb2+, Sn2+ and Hg2+ at 10 mM concentrations. TLC analysis showed that the enzyme is a liquifying alpha-amylase. The enzyme reduced the viscosity of algal biomass suspension up to 74.2 ± 0.17 % which was more efficient than Bacillus amyloliquefaciens alpha-amylase (80.5 ± 0.2 %).