a/k/a Florestor. It's a probiotic yeast which may, or may not also be found in the kombucha SCOBY (symbiotic colony of bacterias and yeasts), however I do not believe Boulardi yeast has been found in kefir.
I make and drink kombucha (as well as kefir), so there's a good possibility that I am consuming boulardi yeast. However, I feel the various 35+ different strains of probiotic bacterias and yeasts found in kefir are more beneficial.
I don't know much about the boulardi yeast in particular, but probiotic bacterias and yeasts can be beneficial in the intestine, replacing harmful bacterias with beneficial ones.
I personally feel they are extremely beneficial, but everyone is different and there are others who have not experienced much, if any, benefit from taking probiotics. There are also some who may develop allergic reactions to certain types of probiotics derived from milk, who may do better supplementing with boulardi yeast, which is derived from natural yeasts on skins of tropical fruits.
Antibiotics destroy bacteria, both good and bad, but apparently have little effect on yeasts, so while taking antibiotics, taking a probiotic yeast supplement may be especially beneficial.
