New generation probiotics: combining probiotic and biotechnological potential of Kluyveromyces marxianus.

Kluyveromyces marxianus has high biotechnological potential, particularly because it can utilize a wide range of substrates and grow faster than other yeasts. It has also attracted interest as a prospective probiotic; however, this application is still not well researched. Two K. marxianus strains with promising biotechnological properties and the proven ability to efficiently produce 2-phenylethanol (2-PE) and ethanol were examined in this study to evaluate their potential as probiotics. Yeasts WUT216 and WUT240 exhibited similar survival rates in a simulated human digestive system as the reference K. marxianus strain B0399 (DiarYeast®, LongLife, Milano, Italia). Additionally, the WUT yeasts revealed a high degree of adhesion to cancer and normal cell lines in vitro. Importantly, the WUT strains did not exhibit undesirable characteristics, such as mucolytic and hemolytic activities, and toxic effects on the Caco-2 cell lines in vitro and on Galleria mellonella larvae in vivo. Furthermore, K. marxianus strains displayed attractive probiotic properties, particularly high antioxidant potential, antifungal activity, and significant β-glucan content. This study also showed that the WUT yeasts are sensitive to the commercial antifungals, fluconazole, amphotericin B, and geneticin G418. Overall, the WUT240 and WUT216 exhibit similar probiotic properties to those of B0399. Thus, the WUT yeasts are not only promising producers of 2-PE and ethanol but also attractive probiotic candidates. Additionally, discrepancies in literature reports regarding the analyses conducted were noted, particularly in adhesion and autoaggregation tests. KEYPOINTS: • K. marxianus strains combine probiotic with its biotechnological potential • WUT yeasts may positively affect the host (antioxidants, β-glucan, antimicrobials) • Methodological differences hinder the comparison of potential probiotics.