Lactose-induced expression of Bacillus sp. TS-23 amylase gene in Escherichia coli regulated by a T7 promoter.

Bacillus sp. TS-23 amylase gene was amplified by polymerase chain reaction and cloned into the pET23(+) transcription vector. Lactose induction of Escherichia coli BL21(DE3) cells harbouring this recombinant plasmid resulted in the extracellular production of gene products. By the addition of 20 mmol l-1 lactose, the amylase activity of fermentation broth had a specific activity of 21 U mg-1 of protein.