Dr. Ed van Niel
Dr. Magnus Carlquist
Physiology of lactic acid bacteria
Lactic acid bacteria (LAB) are used in the dairy industry and other industries based on their interesting products formed through fermentations and some of them for their probiotic properties. In a typical fermentation process of LAB consisting of more than one unit operation, the bacterial cells are exposed to different environmental conditions and as a consequence they regulate their physiological state in pursuit of reaching optimal fitness. Individual cells stand in dynamic equilibrium with the surrounding environment and modulate their composition, structure and metabolic status in a predefined manner that benefit the survival of the entire population. For the bacterium to perform optimally in a new environment, either as inoculum resuming growth in a large-scale fermenter or to survive long-term storage after freeze-drying, they need to have an optimal prerequisite to stand the environmental transition. Cell responses to specific changes in conditions occur on many planes and by different mechanisms operating on different time scales.
At the Division of Applied Microbiology, a diverse set of bio-technologies (ranging from genetic engineering and flow cytometry to growth studies through fermentations in bioreactors and kinetic modelling) are used to analyze molecular, structural and physiological responses of Lactobacilli cells, both at the single-cell and at the cell population level, when applying various process design strategies. Our current focus point is to improve our understanding of the connection between individual cells energy/redox status and metabolic activity and major structural and physiological adjustments required to survive freeze-drying stress.