[Molecular cloning of alpha-amylase gene from Bacillus megaterium and its expression in Bacillus subtilis]

Using Bacteriophage lambda and plasmid pAT153 and pNQ122 as vectors, alpha-Amylase gene from B. megaterium has been cloned into both hosts of E. coli and B. subtilis. Expression level of the gene is 250 times higher than B. megaterium when it resides in B. subtilis. The enzyme produced by B. subtilis harboring the hybrid plasmid can digest amylase into maltose and maltotriose at first, then turn them to maltose and glucose, as incubation time extended. It also can digest maltotriose to maltose and glucose. As a control, the extracts from the broth of recipient strain have no detectable amylase activities. Therefore the enzyme coded by this gene is defined as saccharifying type alpha-amylase. Its molecular weight is about 58,000 daltons.