Fuente: "milk OR dairy products" J Dairy Sci. 2026 May 29:S0022-0302(26)02870-5. doi: 10.3168/jds.2026-28435. Online ahead of print.ABSTRACTKefir, a fermented milk product comprising complex consortia of bacteria and yeasts, develops its characteristic flavor through coordinated microbial interactions. In this study, we investigated flavor compound biosynthesis and development by kefir-derived lactic acid bacteria and yeast during kefir fermentation, integrating genome-based predictions with metabolite validation. Metagenomic analysis identified Lactobacillus and Kluyveromyces as predominant genera in both kefir grains and fermented milk kefir. Lentilactobacillus kefiri SLAM023B and Kluyveromyces marxianus SLAM005Y were isolated and subjected to hybrid genome sequencing on Illumina and Nanopore platforms. Functional annotation via KEGG pathway mapping revealed featured pathways including amino acid and fatty acid metabolism, as well as interconversion of alcohol, aldehyde, and acid, contributing to the formation and generation of flavor compounds. Notably, K. marxianus SLAM005Y produced fruity fusel alcohols, whereas L. kefiri SLAM023B contributed fatty acid-derived precursors. The coculture of the 2 strains significantly enhanced ester synthesis, particularly ethyl acetate and isoamyl acetate, imparting fruity and creamy sensory notes to the fermentation profile. In addition, increases in ethyl octanoate and C6/C8 fatty acids introduced fruity and cheese-like characteristics, while levels of grassy aldehydes were reduced. Correlation analysis supported the complementary metabolic roles and potential cross-feeding mechanisms between the strains, which help explain the development of kefir flavor. Taken together, this study provides a genomic and functional framework to examine cooperative metabolism in kefir and identifies molecular targets for improving the sensory properties of fermented dairy products.PMID:42217781 | DOI:10.3168/jds.2026-28435