Over-expression system for secretory phospholipase D by Streptomyces lividans

The structural gene for phospholipase D (PLD) of an actinomycete, Streptoverticillium cinnamoneum, together with its promoter region was introduced into Streptomyces lividans using a shuttle vector-pUC702-for Escherichia coli and S. lividans. The transformant was found to secrete a large amount of PLD (about 2.0x10(4) U/l, 42 mg/l) when cultured in a jar fermentor. Both an initial glucose concentration of 17.5 g/l and the feeding of carbon and nitrogen sources are effective for efficient secretion of PLD; under these culture conditions, the amount of PLD secreted reached a maximum level (about 5.5x10(4) U/l, 118 mg/l) after about 60 h. In contrast to the original producer, Stv. cinnamoneum, which secretes only a small amount of PLD (about 1.1x10(3) U/l, 2 mg/l) along with other extracellular proteins, this heterologous expression system is markedly more efficient in production of secretory PLD.