Complex inducible promoter system derivable from a phage of a lactic acid bacterium (lab), and the use in a lab for production of a desired protein

The invention provides a complex inducible promoter system derivable from a phage of a lactic acid bacterium, especially one having the DNA sequence of SEQ. ID. NO: 3 given in Figure 2, or a DNA sequence essentially corresponding to those sequences, and a modification of (an essential part of) such promoter system in which the mitomycin C induction system is replaced by a food-grade system, e.g. a temperature-initiated induction system or a salt-initiated induction system. Also is provided a recombinant vector and a transformed lactic acid bacterium comprising (an essential part of) such promoter system. Further a process for producing a desired protein by such transformed bacterium is provided, comprising expressing a gene encoding said desired protein or a precursor thereof under control of such promoter system or an essential part thereof. Preferably the transformed lactic acid bacterium is made food-grade due to using food-grade DNA sequences and/or removing non-food-grade DNA sequences. When required, the desired protein can be secreted by the lactic acid bacterium if a DNA sequence fused to the gene encoding the desired protein is present which effects secretion of the desired protein or its precursor. The process can be used in a fermentation process, in which the desired protein causes lysis of the bacterial cells so that the contents of the cells can be released, or in which the desired protein is an enzyme involved in flavour formation, or in which the desired protein has a function in a cheese production process, such as chymosin or a precursor thereof, or an enzyme involved in flavour formation.