PT  - JOURNAL ARTICLE
AU  - Ton Baars
AU  - Betty van Esch
AU  - Luuk van Ooijen
AU  - Zuomin Zhang
AU  - Pieter Dekker
AU  - Sjef Boeren
AU  - Mara Diks
AU  - Johan Garssen
AU  - Kasper Hettinga
AU  - Remco Kort
TI  - Raw milk kefir: microbiota, bioactive peptides, and immune modulation
AID  - 10.1101/2022.10.19.512868
DP  - 2022 Jan 01
TA  - bioRxiv
PG  - 2022.10.19.512868
4099  - http://biorxiv.org/content/early/2022/10/25/2022.10.19.512868.short
4100  - http://biorxiv.org/content/early/2022/10/25/2022.10.19.512868.full
AB  - This study aims to characterize the microbial and peptidomic composition of raw milk kefir, and to address the potential anti-allergic effects of raw milk kefir using validated research models for food allergy. Raw milk kefir was produced after incubation with a defined freeze-dried starter culture. Kefir was sampled during fermentation at seven-time intervals. For comparison, kefir was also prepared from boiled milk (100 °C; 5 sec). Peptide compositions were determined for the raw and heated milk, plus kefir end products made from these milks. In a murine food allergy model, the two kefir end products were investigated on their allergy modulating effects. In both kefirs, we identified amplicon sequence variants identical to those in the starter, matching the bacteria Lactococcus lactis, Streptococcus thermophilus, Leuconostoc and the yeast Debaromyces. In raw milk kefir, additional sequence variants of Lactococcus lactis and the yeasts Pichia and Galactomyces could be identified, which were absent in heated milk kefir. Analysis of peptide compositions in kefirs indicated that the number and intensity of peptides drastically increased after fermentation. Heating of milk negatively affected the diversity of the peptide composition in kefir. Only raw milk kefir suppressed the acute allergic skin response to the food allergen ovalbumin in sensitised mice. These effects coincided with differences in the T-cell compartment, with lower percentages of activated Th1 cells and IFNg production after treatment with kefir made from heated milk. The results of this study indicate specific properties of raw milk kefir that may contribute to its additional health benefits.Competing Interest StatementTB is partly sponsored for his research activity by the Raw Milk Company. J.G. and B.v.E. are partly employed at Danone Nutricia Research. All other authors report no conflict of interest.ASVAmplicon Sequence VariantcatConcatenatedCFUColony Forming UnitCtCycle thresholdSCDefined Starter Culture eXact® 2 kefir, HansenEVExtracellular VesiclesITSInternal Transcribed SpacerNCBINational Centre for Biotechnology InformationPBSPhosphate Buffered Saline solutionHMHeated Milk (shortly boiled)HMKHeated Milk Kefir based on SCqPCRQuantitative real-time polymerase chain reactionRARelative AbundanceRMRaw MilkRMKRaw Milk Kefir based on SC