A food-grade expression/secretion vector for Lactococcus lactis that uses an α-galactosidase gene as a selection marker

A new food-grade expression/secretion vector for lactococci, pFMN30, was developed using an a-galactosidase gene (melA) of Lactobacillus plantarum as a selection marker. The 4.9-kb pFMN30 is a derivative of the lactococcal vector pMG36e containing a broad-host-range replicon of pWV01. In Lactococcus lactis, transformants carrying the vector were easily detectable by the appearance of a blue colony on a X-a-gal-containing medium and also by the growth on a medium containing melibiose as a sole carbon source. The expression/secretion vector was equipped with the controllable and strong nisA promoter. In addition, uSP45 signal peptide was inserted for the efficient secretion of a foreign protein outside cells. The vector pFMN30 was used for the expression and secretion of (x-amylase as a reporter gene, lacking a signal sequence derived from Bacillus licheniformis in L. lactis. These results show that the food-grade expression/secretion vector constructed in the present study could be used for the production of foreign proteins in L. lactis for the production food materials and also for the medicinal purposes. (c) 2005 Elsevier Ltd. All rights reserved.