Influence of culture pH on survival of Lactobacillus reuteri subjected to freeze-drying

L. reuteri was cultivated at pH 5 and 6. The cells were harvested at 0.5, 2.5 and 4.5 h after entering the stationary phase and their viability after freeze-drying was compared with their viability prior to freeze-drying. The highest viability — approximately 80% of the viability prior to freeze-drying — was obtained for cells from the pH 5 cultures harvested 2.5 h after entering the stationary phase. The time after entering the stationary phase did not influence the viability of the cells from the pH 6 cultures where the viability was approximately 50% irrespective of harvest time. Product formation was the same for pH 5 and pH 6 grown cells, whereas the pH 6 grown cells exhibited a more elongated morphology.