Food-grade vector suitable for transforming a food-grade host cell use of said vector for transforming food-grade host cells and use of said transformed cells in biotransformation processes

A food-grade vector suitable for transforming a food-grade host cell, said vector comprising:

• 1) a nucleic acid which hybridizes with a non-essential portion of chromosomal DNA of a non-transformed host cell enabling said vector to integrate stably into a chromosome of said host cell after transformation to form a transformed host cell without leading to a loss of an essential function of said host cell, wherein said host cell is a lactic acid bacterium;
• and
• 2) foreign DNA selected from the group consisting of
• i. foreign DNA having a DNA sequence that codes for a food-grade selectable marker enabling the transformed host cell to metabolize a substrate that cannot be metabolized by the non-transformed host cell, where at least said DNA sequence and the product encoded by said DNA sequence are foreign for a prototrophic strain of said non-transformed host cell,
• ii. foreign DNA having a DNA sequence that codes for at least one product enabling the transformed host cell to grow in the presence of a food-grade natural bacteriocidal agent wherein at least said DNA sequence and the product encoded by said sequence are foreign for the non-transformed host cell, and
• iii. a mixture of both (i) and (ii);
• the food-grade vector being suitable for transforming a food-grade gram positive bacterial host cell, and the food-grade vector having been made incapable of autonomously replicating in the bacterial host cell by removal of its replicase gene.