Composition of Water Kefir Grains:
Water kefir grains consist of a complex polysaccharide matrix, upon which live a combination of live bacteria and yeasts existing in a symbiotic matrix.
These include 57 lactic acid bacteria strains, some acetic acid bacteria strains, and at least four yeast strains. Up to 453 different bacterial strains have been identified in water kefir! (Some of these are different subspecies of a single strain, however.) Not all strains are present in all water kefir samples. Differences in the behavior of the grains, the speed at which they multiply, and the type of sugar they perform best with may be due to variations in the bacterial makeup of the particular grains.
The following is a list of the major species of active bacteria and yeasts that are generally found in water kefir:
Microbiota of kefir grains: Pogacic_et_al__Microbiota_of_kefir_grains.pdf