Effect of the biomass production conditions on survival of the probiotic yeast Saccharomyces cerevisiae var. boulardii in a laboratory model of the gastrointestinal tract

Saccharomyces cerevisiae var. boulardii is a commercialized probiotic yeast used for the treatment of diarrhea and other disorders of the gastrointestinal tract. While the impact of this yeast on the body and its interaction with other microorganisms is well studied, little information about the production of probiotic yeasts is publicly available. This study aimed to improve the performance of S. boulardii by optimizing yeast biomass production. We developed a simple in vitro model that mimicked the conditions of the gastrointestinal tract. The model allowed us to detect differences in performance between yeast produced under different conditions. The three-step set-up consisted of incubations in stomach-like and small intestine-like juice, followed by cultivation under colon-simulating conditions with intestine-like media (ILM) at varying pH. S. boulardii strains were initially unable to growth in ILM at pH 7.0. However, by optimizing production conditions, we obtained yeast capable of surviving the whole pH range in ILM. Yeast biomass displaying the best performance was harvested in early stationary phase from cultures grown at 37 °C in YPD medium. Moreover, during cultivation under colon-like conditions, we detected acetic acid, which is a desirable feature of probiotic microorganisms. The choice of production conditions is crucial for the quality and functionality of probiotic yeast biomass. Differences in biomass viability can be observed by applying a model of the gastrointestinal system, which can be a useful tool in further studies on probiotic yeasts.