Heterologous expression of Oenococcus oeni malolactic enzyme in Lactobacillus plantarum for improved malolactic fermentation

Lactobacillus plantarum is involved in a multitude of food related industrial fermentation processes including the malolactic fermentation (MLF) of wine. This work is the first report on a recombinant L. plantarum strain successfully conducting MLF. The malolactic enzyme (MLE) from Oenococcus oeni was cloned into the lactobacillal expression vector pSIP409 which is based on the sakacin P operon of Lactobacillus sakei and expressed in the host strain L. plantarum WCFS1. Both recombinant and wild-type L. plantarum strains were tested for MLF using a buffered malic acid solution in absence of glucose. Under the conditions with L-malic acid as the only energy source and in presence of Mn(2+ )and NAD(+), the recombinant L. plantarum and the wild-type strain converted 85% (2.5 g/l) and 51% (1.5 g/l), respectively, of L-malic acid in 3.5 days. Furthermore, the recombinant L. plantarum cells converted in a modified wine 15% (0.4 g/l) of initial L-malic acid concentration in 2 days. In conclusion, recombinant L. plantarum cells expressing MLE accelerate the malolactic fermentation.