A novel saccharifying α-amylase of Antarctic psychrotolerant fungi Geomyces pannorum: Gene cloning, functional expression, and characterization

A DNA segment encoding a novel alpha-amylase was cloned from the Antarctic psychrotolerant fungi Geomyces pannorum. The gene has an open reading frame of 1761 bp, deduced 586 amino acids, revealing a relatively low homology to alpha-amylases from diverse fungal genera. The alpha-amylase gene was overexpressed in Pichia pastoris, and the recombinant alpha-amylase was purified and characterized. Enzymatic activity was optimal at pH 6.0 and 70 degrees C, and the specific activity was 9.78 x 10(3) U/mg when using soluble starch as substrate. Moreover, the enzyme retained more than 90% of its maximum activity over a wide pH range ( 6.0-9.0). Exceptionally, the main hydrolysis products of soluble starch catalyzed by the enzyme were glucose and maltose, of which glucose reached a concentration of 68.8% (w/w). This is the first report on identifying thermophilic fungal amylase from psychrotolerant fungi. Also, the preliminary study on the high-glucose-producing alpha-amylase with detailed enzymatic properties shows a potential application prospect in syrup industry.