Quorum sensing mediated kefir grain extracellular matrix formation hypothesis based on biofilm

Abstract

Kefir possesses numerous health benefits, but its starter kefir grains propagate slowly and can only be cultured from existing grains. To support the optimization of kefir fermentation and the development of functional foods, this study investigated the formation of kefir grain extracellular matrix. Focusing of biofilms and quorum sensing, we explored biofilm formation by dominant strains (one strain of Lentilactobacillus kefiri, one strain of Kluyveromyces marxianus and one strain of Acetobacter fabarum with strong biofilm formation capabilities) isolated from kefir to elucidate the mechanism of extracellular matrix formation. The monosaccharide composition and secondary structures of biofilms and kefir grain extracellular matrix were compared. Additionally, this study analyzed the relationship between biofilm formation by mixed culture of three dominant strains and autoinducer-2 activity and examined biofilms at different time points using scanning electron microscopy and co-aggregation microscopy. The results revealed that the biofilms formed by the mixed strains closely resembled the structure and composition of the kefir grain extracellular matrix and was mediated by quorum sensing. L. kefiri and A. fabarum were observed to encapsulate K. marxianus to form biofilms. This study is the first to provide an understanding of the quorum sensing-mediated formation of the kefir grain extracellular matrix, providing a foundation for transitioning from traditional kefir grain fermentation to design synthetic kefir grains.