Abstract: Kefir is a kind of natural mixed bacteria fermented dairy products, which mainly contains specific microbial communities such as lactic acid bacteria, yeast and acetic acid bacteria, and it presents good flavor and function. However, the formation mechanism of kefir grain is not clear at present, and it is generally believed that the formation of kefir granules is based on bacterial biofilm as the precursor. This paper reviews the microbial diversity of Kefir in different regions and the effects of microorganisms on the function and flavor of fermented milk, as well as the microbial interactions in Kefir and colony succession during fermentation. The biofilm formation related to Kefir grain formation process was introduced in order to provide some reference for the study of Kefir grain formation mechanism.

Key words: Kefir, Microorganism, Interaction, biofilm