Effect of microbial aggregation and biofilm formation on kefir grain formation

Kefir grain is a natural starter culture, and the original grain can grow and split to produce new Kefir grains after long-term subculturing in milk. The grain formation properties of the Kefir grain have attracted considerable research attention. However, synthetic Kefir grains still cannot be obtained due to the complex microbial system and the grain composition. Kefir grain formation is a complex process, and can be affected by the microbial strains present, proteins, polysaccharides, and other components. Therefore, based on results from recent studies, the diversity and distribution of microorganisms in Kefir grains were investigated and the effects of the microorganisms, proteins, and polysaccharides in the Kefir grain on microbial strain aggregation and biofilm formation were discussed. Subsequently, the features of Kefir grain formation were summarized based on the aggregation and biofilm formation abilities of the microorganisms. These findings can help to reveal the mechanism underlying Kefir grain formation, establish new methods for synthesizing artificial Kefir grains, and provide new approaches for developing Kefir products.