Growth of yeast contaminants in an immobilized lactic acid bacteria system

Calcium alginate‐immobilized lactic acid bacteria (LAB) were used to acidify milk and re‐utilized for five successive fermentations. The yeast Kluyveromyces marxianus was added to the milk in order to simulate contamination of the bioreactor. Growth of the yeast was studied over the successive re‐utilizations of the immobilized LAB. When the system was contaminated only in the first fermentation, the yeast population decreased in the successive re‐utilizations; rinsing of the system following each fermentation was effective in further reducing yeast contamination. Yeast population increased only when contaminants were added at the beginning of each fermentation. Presence of yeast in the system did not influence acidification rate of the immobilized LAB or cell release from the alginate beads.