Secretion of Bacillus α-amylase from yeast directed by glucoamylase I signal sequence of Saccharomyces diastaticus

Abstract

For the secretion of Bacillus stearothermophilus α-amylase from yeast, a recombinant plasmid pGAT17 was constructed by fusing B. stearothermophilus a -amylase structural gene in frame to the promoter and signal sequence of Saccharomyces diastaticus glucoamylase I gene (STA1). The secretion of the heterologous α-amylase from S. diastaticus transformed with pGAT17 was confirmed by the halo formation around colonies on selective starch agar medium. About 80% of the total α-amylase activity was detected in the extracellular culture medium. The secreted α-amylase was glycosylated and its molecular weight increased from 61 kDa to 75 kDa. The thermostability of the the glycosylated a -amylase was markedly enhanced, compared with that of the non-glycosylated enzyme from E. coli.