Molecular Genetic Characterization of Commercial Probiotics Saccharomyces boulardii (Enterol®, Biocodex) and Baker’s (Cosm-O-tentic®, Puratos) Yeasts

Saccharomyces boulardii is widely distributed throughout the world. Storage in various laboratories leads to the accumulation of independent genetic changes. To introduce the S. boulardii strain into scientific use, and, particularly, in space biology, it must be thoroughly characterized. Since it lacks genetic markers, simple methods for identifying the probiotic strain and distinguishing it from laboratory strains of Saccharomyces cerevisiae must be developed. In addition, it is necessary to select appropriate genetic systems for monitoring genetic stability. We have characterized three strains as potential space flight objects, derived from preparations—the well-known Enterol® (Biocodex), based on S. boulardii strain CNCM I-745, and Cosm-O-tentic® (Puratos). The combined characteristics are consistent with S. cerevisiae; the species assignments of the Puratos isolates remain provisional because their D1/D2 comparisons were not taxonomically conclusive. However, isolates show differences in nucleotide sequences, ploidy, structure of MAL and CUP1 loci, and antifungal susceptibility. Copper sensitivity and fungicide susceptibility are candidate markers for future genetic-stability studies; their reliability during serial passage or storage and the genetic basis of any phenotypic changes require validation.