Characterization of metabolism and robustness of Lactococcuccus lactis under different fermentation conditions for production of starter cultures with improved robustness

Research Project, 2014 – 2016

Starter cultures of Lactococcus lactis are used for the production of fermented food. The shelf life and quality of the starter culture depend on the robustness of the cells. Cellular robustness, i.e. tolerance to general and specific stress, is highly dependent on the detailed cellular composition and the ability of the cell to synthesize specific metabolites and/or proteins. Respiro-fermentative production of L. lactis results in increased cell mass yield, but the robustness of resulting starter cultures is compromised. The proposed project aims at defining the correlation between the metabolic status of L.lactis, induced by specific fermentation conditions, and the robustness of the resulting starter cultures. Batch fermentations under fermentative and respiro-fermentative conditions will be set-up and characterized in terms of protein expression and metabolite profiles, and potential robustness markers will be identified. In order to determine the critical factors of the cultivation process that influence the cellular robustness, chemostat cultivations will be characterised under fermentative, respiro-fermentative and fully respiratory conditions, using state-of-the-art omics tools. This approach will allow a precise characterization of L. lactis metabolism and will greatly contribute to pinpointing the best process for improved robustness. The study will define improvements for optimisation of the fermentation step in the current production of starter cultures.