Bacterial diversity, bioactive peptides, and enhanced immunomodulatory effects in raw milk kefir made with defined starter cultures versus backslopping

Ton Baars; Betty van Esch; Mara Diks; Luuk van Ooijen; Zuomin Zhang; Pieter Dekker; Sjef Boeren; Johan Garssen; Kasper Hettinga; Remco Kort

doi:10.1016/j.idairyj.2025.106202

Bacterial diversity, bioactive peptides, and enhanced immunomodulatory effects in raw milk kefir made with defined starter cultures versus backslopping

Ton Baars^*, Betty van Esch, Mara Diks, Luuk van Ooijen, Zuomin Zhang, Pieter Dekker, Sjef Boeren, Johan Garssen, Kasper Hettinga, Remco Kort^*

^*Corresponding author for this work

Research output: Contribution to journal › Article › Academic › peer-review

Abstract

This study compared the microbial composition, peptide profiles, and immunomodulatory effects of raw milk kefir produced using a defined starter culture (RMK-S) versus backslopping (RMK-B). RMK-B exhibited significantly higher microbial loads, with a 10-fold increase in total plate counts and 35-fold increase in lactic acid bacteria compared to RMK-S. This correlated with higher peptide content in RMK-B kefir, though RMK-S displayed higher bacterial diversity and a more diverse, bioactive peptide pool. Microbial analysis revealed RMK-S retained the starter culture's profile, while RMK-B was dominated by Lactococcus lactis and consistent yeast species, including Kazachstania, Klyveromyces, and Galactomyces. In a murine food allergy model, RMK-S kefir significantly reduced the allergic skin response and increased IFN-γ production, demonstrating enhanced immune modulation. RMK-B did not exhibit these protective effects. These findings point towards the role of bacterial diversity and peptide composition in kefir's health benefits, favoring defined starter cultures over backslopping.

Original language	English
Article number	106202
Number of pages	9
Journal	International Dairy Journal
Volume	164
DOIs	https://doi.org/10.1016/j.idairyj.2025.106202
Publication status	Published - May 2025

Bibliographical note

Publisher Copyright:
© 2025 The Authors

Funding

Software AG Stiftung, Darmstadt, Germany (grant ID P12642) for funding the murine allergy study. Raw Milk Company, De Lutte, The Netherlands, for providing the milk and kefir samples in this study, as well as funding for microbial enumeration experiments.

Funders	Funder number
Software AG – Stiftung	P12642

Keywords

Backslopping
Bioactive peptides
Immunomodulation
Kefir using starter cultures
Microbial composition
Raw milk kefir

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10.1016/j.idairyj.2025.106202Licence: CC BY

1-s2.0-S0958694625000214-mainFinal published version, 4.77 MBLicence: CC BY

Cite this

Baars, T., van Esch, B., Diks, M., van Ooijen, L., Zhang, Z., Dekker, P., Boeren, S., Garssen, J., Hettinga, K., & Kort, R. (2025). Bacterial diversity, bioactive peptides, and enhanced immunomodulatory effects in raw milk kefir made with defined starter cultures versus backslopping. International Dairy Journal, 164, Article 106202. https://doi.org/10.1016/j.idairyj.2025.106202

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abstract = "This study compared the microbial composition, peptide profiles, and immunomodulatory effects of raw milk kefir produced using a defined starter culture (RMK-S) versus backslopping (RMK-B). RMK-B exhibited significantly higher microbial loads, with a 10-fold increase in total plate counts and 35-fold increase in lactic acid bacteria compared to RMK-S. This correlated with higher peptide content in RMK-B kefir, though RMK-S displayed higher bacterial diversity and a more diverse, bioactive peptide pool. Microbial analysis revealed RMK-S retained the starter culture's profile, while RMK-B was dominated by Lactococcus lactis and consistent yeast species, including Kazachstania, Klyveromyces, and Galactomyces. In a murine food allergy model, RMK-S kefir significantly reduced the allergic skin response and increased IFN-γ production, demonstrating enhanced immune modulation. RMK-B did not exhibit these protective effects. These findings point towards the role of bacterial diversity and peptide composition in kefir's health benefits, favoring defined starter cultures over backslopping.",

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author = "Ton Baars and {van Esch}, Betty and Mara Diks and {van Ooijen}, Luuk and Zuomin Zhang and Pieter Dekker and Sjef Boeren and Johan Garssen and Kasper Hettinga and Remco Kort",

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AU - Zhang, Zuomin

AU - Dekker, Pieter

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AU - Hettinga, Kasper

AU - Kort, Remco

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Bacterial diversity, bioactive peptides, and enhanced immunomodulatory effects in raw milk kefir made with defined starter cultures versus backslopping

Abstract

Bibliographical note

Funding

Keywords

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