Construction of α-amylase-producing strains not subject to carbon catabolite repression

The dyatic symmetric element (DSE) present in the α-amylase gene promoter region of the thermophilic Streptomyces strain sp. TO1, and the whole α-amylase gene (amy TO1) with a 3-bp change in the DSE, were cloned in the high copy number replicative cloning vector pIJ702 giving pLM10 and pLM11 plasmids respectively. In TO1/pLM10 and Streptomyces lividans TK24/pLM11 strains, the expression of α-amylase TO1 gene became insensible to the negative effect of glucose and glycerol. These results strongly suggest that, in a high copy number system, the negative transcriptional regulator was titrated out by the DSE and the repression of the expression of amy TO1 gene is abolished. [Copyright &y& Elsevier]