Cloning and expression of a Bacillus coagulans amylase gene in Escherichia coli

A partial EcoRI fragment of Bacillus coagulans DNA cloned in an Escherichia coli K12 bacteriophage lambda host-vector system was shown to direct the synthesis of a thermostable alpha-amylase whose activity could be detected in situ on petri plates using the iodine staining method. A 3.31 kb EcoRI fragment containing the active gene with its own promoter was subcloned in pBR322; in the new clone, called pAMY2, the amylase was shown to accumulate in the periplasmic space. The molecular weight of the enzyme, confirmed by in vivo labelling of plasmid products in minicells, was estimated to be 60000. The restriction map of the plasmid was determined for five restriction enzymes and two new plasmids with smaller DNA inserts were constructed, both directing the synthesis of amylase; one of them with a 2.2 kb PstI insert was shown to be responsible for the synthesis of a fused beta-lactamase-alpha-amylase protein with amylase activity.