Vulvovaginal candidiasis is the most prevalent vaginal infection worldwide and Candida albicans is its major agent. Vulvovaginal candidiasis is characterized by disruption of the vaginal microbiota composition, as happens following large spectrum antibiotic usage. Recent studies support the effectiveness of oral and local probiotic treatment for prevention of recurrent vulvovaginal candidiasis. Saccharomyces cerevisiae is a safe yeast used as, or for, the production of ingredients for human nutrition and health. Here, we demonstrate that vaginal administration of probiotic Saccharomyces cerevisiae live yeast (GI) and, in part, inactivated whole yeast Saccharomyces cerevisiae (IY), used as post-challenge therapeutics, was able to positively influence the course of vaginal candidiasis by accelerating the clearance of the fungus. This effect was likely due to multiple interactions of Saccharomyces cerevisiae with Candida albicans. Both live and inactivated yeasts induced coaggregation of Candida and consequently inhibited its adherence to epithelial cells. However, only the probiotic yeast was able to suppress some major virulence factors of Candida albicans such as the ability to switch from yeast to mycelial form and the capacity to express several aspartyl proteases. The effectiveness of live yeast was higher than that of inactivated whole yeast suggesting that the synergy between mechanical effects and biological effects were dominant over purely mechanical effects. The protection of epithelial cells to Candida-induced damage was also observed. Overall, our data show for the first time that Saccharomyces cerevisiae-based ingredients, particularly the living cells, can exert beneficial therapeutic effects on a widespread vaginal mucosal infection.

A methodology was developed to quantify the efficiency of yeast-based products for adsorption of three mycotoxins: zearalenone (ZEA), aflatoxin B(1) (AFB(1)), and ochratoxin A (OTA). Eight products were tested (yeast cell wall or inactivated yeast). The described experimental protocol based on in vitro tests provided reliable isotherms for each mycotoxin. The most suitable models were the Hill model for ZEA, the Langmuir model for AFB(1), and the Freundlich model for OTA. From these models, original mathematical affinity criteria were defined to quantify the product adsorption performances for each mycotoxin. The best yeast product, a yeast cell wall from baker's yeast, can adsorb up to 68% of ZEA, 29% of AFB(1), and 62% of OTA, depending on the mycotoxin concentrations. The adsorption capacity largely depended both on yeast composition and mycotoxin, but no direct correlation between yeast composition and adsorption capacity was found, confirming that adsorption of mycotoxin on yeast-based products involves complex phenomena. The results of this study are useful for comparing the adsorption efficiency of various yeast products and understanding the mechanisms involved in adsorption.

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To date, no official method is available to accurately define the binding capacity of binders. The goal is to define general in vitro parameters (equilibrium time, pH, mycotoxin/binder ratio) for the determination of binding efficacy, which can be used to calculate the relevant equilibrium adsorption constants. For this purpose, aflatoxin B1 (AFB1), zearalenone (ZEA) or ochratoxin A (OTA) were incubated with one yeast cell wall in pH 3, pH 5 or pH 7 buffers. The percentage of adsorption was recorded by quantitation of remaining mycotoxins in the supernatant and amount of mycotoxin adsorbed on the residue. The incubation of yeast cell wall in the presence of mycotoxins solved in buffer, lead to unexpected high adsorption percentage when the analysis was based only on remaining mycotoxins in the supernatant. The decrease of mycotoxins in the supernatant was not correlated to the amount of mycotoxins found in the residue. For this reason we modified the conditions of incubation. Yeast cell wall (5 mg) was pre-incubated in buffer (990 μl) at 37 °C during 5 min and then 10 μl of an alcoholic solution of mycotoxin (concentration 100 times higher than the final concentration required in the test tube) were added. After incubation, the solution was centrifuged, and the amount of mycotoxins were analysed both in the supernatant and in the residue. A plateau of binding was reached after 15 min of incubation whatever the mycotoxins and the concentrations tested. The adsorption of ZEA was better at pH 5 (75 %), versus 60 % at pH 3 and 7. OTA was only significantly adsorbed at pH 3 (50 %). Depending on the pH, the adsorptions of OTA or ZEA were increased or decreased when they were together, indicative of a cooperative effect.