kefiran

Kefiran is an extracellular polysaccharide produced by certain lactic acid bacteria, most notably Lactobacillus kefiranofaciens, during the fermentation of kefir grains. Kefir grains are a symbiotic community of bacteria and yeasts embedded in a gel-like matrix, and kefiran is a major component of this matrix. The polymer also contributes to the texture and rheology of the kefir beverage.

Chemically, kefiran is a water-soluble heteropolysaccharide composed primarily of glucose and galactose units. The exact repeating structure can vary, but the polymer forms long chains that can bind water and create viscous solutions and gels even at relatively low concentrations. This gives kefir its characteristic thickness and stability.

Physically, kefiran enhances the viscosity and stabilizes emulsions in kefir, aiding suspension of components and influencing mouthfeel. Beyond its role in kefir, kefiran is studied for properties typical of biopolymers, such as the ability to form biocompatible hydrogels and to interact with other polymers.

Applications and research are focused on food and potential biomedical uses. In foods, kefiran is investigated as a thickener or stabilizer and as a texturing agent. In biomedicine and biotechnology, kefiran-based hydrogels and composite materials are explored for wound dressings, drug delivery, and tissue engineering, owing to biocompatibility and gel-forming capabilities. Some studies report antimicrobial, antioxidant, or immunomodulatory activities, but results vary and clinical relevance remains to be established.

Production and extraction are linked to the fermentation process of kefir grains, with interest in optimizing yield and purity for research and industrial applications.