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

Researchers: Bettina Lorantfy, Valeria Mapelli, Carl Johan Franzén and Lisbeth Olsson

Lactic acid bacteria have been used for cheese making and other fermented milk products for thousands of years, thanks to their capability for milk acidification. Nowadays, in the dairy industry, starter cultures are commercially produced for cheese making, mainly via anaerobic batch fermentations. The fermentation part of the production is followed by a chain of downstream operations, where starter cultures are, for example, freeze-dried. It was recently found that lactic acid bacteria are able to sustain respiratory metabolism when an exogenous source of hemin, an iron containing heterocyclic molecule, is added to the growth medium under aerobic conditions. Hemin allows in fact the electron transport chain for respiration to be completed. Respiration is energetically beneficial for the cells, and under respiratory conditions, higher biomass yield is produced and a by-product pattern different than the one obtained under fully fermentative metabolism is experienced.

The aim of this project is to investigate how different culture conditions; anaerobic, aerobic, and respiratory of lactic acid bacteria influence the robustness of the cells. Combining batch and continuous cultivations, and applying different omics-techniques, the main objective of this work is to find possible robustness markers for the freeze dried starter culture end product.

Better scientific understanding of the switching to respiration could help in finding answers to changes in the culture performance between the different cultivation conditions with respect to robustness.

The project is financed by FORMAS. We collaborate with the Danish company Chr. Hansen in this project.

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Published: Thu 09 Jul 2015. Modified: Thu 08 Dec 2016