Application of microplate scale fluorochrome staining assay for assessment of viability and stability of probiotic Bifidobacterium sp.

Hanna-Leena Alakomi, Jaana Mättö, Anu Vaari, Ilkka Virkajärvi, Maria Saarela

    Research output: Chapter in Book/Report/Conference proceedingConference abstract in proceedingsScientific

    Abstract

    Probiotic cultures encounter harsh conditions during production and in the GI-tract. There is a need for rapid and reliable methods predicting survival and activity of the probiotic cultures in various applications. In this study we describe a fluorescence staining assay for the determination of viability of Bifidobacterium cells in microplate scale. LIVE/DEAD BacLight Bacterial Viability Kit (SYTO9 and propidium iodide) was utilized for viability testing of fresh and freeze-dried Bifidobacterium cells and the fluorescence intensity was detected by a microplate fluorometer. Validation of the microplate scale assay was performed by comparing results to colony forming units, fluorescence microscopy and spectroscopy. Fresh and freeze-dried B. animalis cultures treated in acidic conditions (pH 2.5 and pH 3.0 alone and in combination with pepsin) or stored at different temperatures were used to study the applicability of the microplate assay for viability assessment of stressed cells. To reveal changes in membrane functions during acid treatment, DIBAC4 (a potentiometric fluorochrome) was additionally used for the analysis of the acid treated cells. In general, the results obtained with the microplate assay were comparable with plate count analysis and fluorescence microscopy. Microplate assay with viability stains gave an estimate of the viability of the probiotic preparations (detection level 106 cfu and the assay was applicable also for acid-treated cells. In the acid tolerance test, B. animalis was sensitive to pH 2.5, although pepsin had clearly protective effect in acidic conditions. Potentiometric measurements with DiBAC4 fluorochrome indicate that acidic conditions caused hyperpolarization of the cell membrane in B. animalis cells. Benefits from the fluorochromic viability assays are that changes in cell state in probiotic preparations can be estimated earlier compared to the results obtained with traditional cultivation methods.
    Original languageEnglish
    Title of host publication The Food, GI-tract Functionality and Human Health Cluster: 3rd PROEUHEALTH Workshop
    Subtitle of host publicationAbstracts and posters
    Place of PublicationEspoo
    PublisherVTT Technical Research Centre of Finland
    Pages55-55
    ISBN (Electronic)951-38-6290-9
    ISBN (Print)951-38-6289-5
    Publication statusPublished - 2004
    EventThe Food, GI-tract Functionality and Human Health Cluster: 3rd PROEUHEALTH Workshop - Sitges, Spain
    Duration: 15 Mar 200417 Mar 2004

    Publication series

    SeriesVTT Symposium
    Number232
    ISSN0357-9387

    Workshop

    WorkshopThe Food, GI-tract Functionality and Human Health Cluster
    CountrySpain
    CitySitges
    Period15/03/0417/03/04

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