A new salt inducible expression system for Lactococcus lactis

A new expression system for Lactococcus lactis based on the salt inducible BusA promoter and the BusR repressor gene of L. lactis MG1363 was developed. To achieve salt induction, the expression of BusR was modulated by introducing mutations to its promoter sequence. An activity of 6.0 μkat l−1 of the model enzyme Lactobacillus amylovorus α-amylase was achieved in the bioreactor cultivation. The major advantage of the current expression system is that no additions of inducing agents are needed into bioreactor cultivations.