Effect of the fermentation pH on the storage stability of Lactobacillus rhamnosus preparations and suitability of in vitro analyses of cell physiological functions to predict it

• Published in: Journal of applied microbiology 2009-04, Vol.106 (4), p.1204-1212
• Main Authors: Saarela, M.H, Alakomi, H.-L, Puhakka, A, Mättö, J
• Format: Article
• Language: English
• Subjects: Bile; Biological and medical sciences; Cell Membrane - physiology; Cryoprotective Agents - pharmacology; Fermentation; Food Preservation - methods; Freeze Drying; Fruit; fruit juice; fruit juices; Fundamental and applied biological sciences. Psychology; Hydrochloric Acid - pharmacology; Hydrogen-Ion Concentration; Lactobacillus rhamnosus; Lactobacillus rhamnosus - drug effects; Lactobacillus rhamnosus - growth & development; Lactobacillus rhamnosus - physiology; Malates - pharmacology; Malus; Membrane Potentials - drug effects; Microbial Viability; Microbiology; Probiotics; stability
• ISSN: 1364-5072; 1365-2672
• DOI: 10.1111/j.1365-2672.2008.04089.x

To investigate how cell physiological functions can predict the stability of freeze-dried probiotics. In addition, the effect of the fermentation pH on the stability of probiotics was investigated. Fermenter-grown (pH 5·8 or 5·0) Lactobacillus rhamnosus cells were freeze-dried and their survival was evaluated during storage at 37°C, in apple juice and during acid [hydrochloric acid (HCl) and malic acid] and bile exposure. Cells grown at pH 5·0 were generally coping better with acid-stress than cells grown at pH 5·8. Cells were more sensitive to malic acid compared with HCl. Short-term stability results of Lact. rhamnosus cells in malic acid correlated well with the long-term stability results in apple juice, whereas the results of cell membrane integrity studies were in accordance with bile exposure results. Malic acid exposure can prove useful in evaluating the long-term stability of probiotic preparations in apple juice. Fermentation at reduced pH may ensure a better performance of Lact. rhamnosus cells during the subsequent acid-stress. The beneficial effect of lowered fermentation pH to Lact. rhamnosus stability during storage in apple juice and the usefulness of malic acid test in predicting the stability were shown.