Exogenous Indole-3-Acetic Acid Induced Ethanol Tolerance in Phylogenetically Diverse Saccharomycetales Yeasts.

Indole-3-acetic acid (IAA) is an exogenous growth regulatory signal that is produced by plants and various microorganisms. Microorganisms have been suggested to cross-communicate with each other through IAA-mediated signaling mechanisms. The IAA-induced tolerance response has been reported in several microorganisms, but has not yet been described in Saccharomycetales yeasts. In the present study, three common stressors (heat, osmotic pressure, and ethanol) were examined in relation to the influence of a pretreatment with IAA on stress tolerance in 12 different lineages of Saccharomyces cerevisiae. The pretreatment with IAA had a significant effect on the induction of ethanol tolerance by reducing the doubling time of S. cerevisiae growth without the pretreatment. However, the pretreatment did not significantly affect the induction of thermo- or osmotolerance. The IAA pretreatment decreased the lethal effects of ethanol on S. cerevisiae cells. Although yeasts produce ethanol to outcompete sympatric microorganisms, IAA is not a byproduct of this process. Nevertheless, the accumulation of IAA indicates an increasing number of microorganisms, and, thus, greater competition for resources. Since the "wine trait" is shared by both phylogenetically related and distinct lineages in Saccharomycetales, we conclude that IAA-induced ethanol tolerance is not specific to S. cerevisiae; it may be widely detected in both pre-whole genome duplication (WGD) and post-WGD yeasts belonging to several genera of Saccharomycetales.

In Vitro Properties of Potential Probiotic Indigenous Yeasts Originating from Fermented Food and Beverages in Taiwan.

Probiotics are live microorganisms that may be able to help prevent and treat some illnesses. Most probiotics on the market are bacterial, primarily Lactobacillus. Yeast are an inevitable part of the microbiota of various fermented foods and beverages and have several beneficial properties that bacteria do not have. In this study, yeast strains were isolated from fermented food and beverages. Various physiological features of the candidate probiotic isolates were preliminarily investigated, including bile salt and acid tolerance, cell surface hydrophobicity, autoaggregation, antioxidant activity, and ß-galactosidase activity. Several yeast strains with probiotic potential were selected. Overall, Kluyveromyces marxianus JYC2614 adapted well to the bile salt and acid tolerance test; it also had favorable autoaggregation and good cell-surface hydrophobicity. Klu. marxianus JYC2610 grew well according to the bile salt and acid tolerance test and performed well regarding cell surface hydrophobicity and ß-galactosidase activity. Selected yeast species can survive in a gastrointestinal environment and should be further evaluated in vivo as probiotics in the future. Our findings should encourage further studies on the application of the strains in this study as food and feed supplements.