Lactic acid bacteria - Characterization of respiratory physiology and development of stress tolerance in Lactococcus lactis for high yield production of robust high performance starter cultures

​This project is carried out in the group of Industrial Biotechnology and in close collaboration with the dairy company Chr. Hansen.

Researchers: Anna Sandersen, Carl Johan Franzén, Lisbeth Olsson

The aim of the project is to understand the cellular behavior at respiratory, fermentative and respiro/ fermentative conditions and how it is related to cellular robustness.

Lactic Acid Bacteria (LAB) are used worldwide within dairy industries as starter cultures in industrial production of varied fermented foods. Manufacturing control and reproducibility is crucial for dairy companies why starter cultures must have known and guaranteed fermentation performance. The quality of starter cultures is directly linked to the conditions the cells have been exposed to throughout production.
Lactococcus lactis, a common used LAB in hard and semi-hard cheese production, has previously been regarded only as a fermentative anaerobic microorganism producing mainly lactic acid. However, in the presence of oxygen and exogenous heme respiratory metabolism can be established where the metabolic product profile is changed to acetate, acetoin and diacetyl beside lactic acid. Furthermore respiration results in increased cell yield compared to anaerobic conditions and it affects the cellular robustness. Though it is not yet understood how and why the metabolic and physiological differences have impact on the cellular robustness.

In this project we want to identify the metabolic and physiological differences between fermentative, respiro-fermentative, and respiratory metabolism in batch and continuous cultivations by using metabolomics and cellular activity after freezing and freeze-drying. The long-term goal is to redesign and optimize the batch production process with high final cell biomass concentration and excellent cellular robustness.

If Chr. Hansen is able to better understand the cellular mechanism influencing cell robustness, the company will be able to bring added value to its customers by ensuring a product with a consistent high quality and a higher profit margin. Moreover, higher yield of viable cells will have a direct financial impact on Chr. Hansen’s cost of production as well as fermentation capacity.

The project is funded by the Danish Agency of Science, Technology and Innovation.

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