Synergistic action of thermal and ethanolic stress in industrial Saccharomyces cerevisiae strains

Abstract

Saccharomyces cerevisiae is widely used for the production of food and biofuels, mainly in the production of bioethanol due to its efficiency in converting substrates. However, stress factors can be toxic, damaging yeast metabolism. In this sense, this study aimed to analyze the impacts of thermal and ethanolic stress on the industrial strains of S. cerevisiae, Fleischmann® and Pedra-2, to guarantee efficiency and viability in industrial conditions. A pre-inoculum was made by adding 0.10 g of lyophilized yeas to 1 mL of saline solution (0.85%), and 400 µL were inoculated in Petri dishes, previously prepared with Sabouraud Agar and incubated at 30 °C. The grown colonies were transferred to fermentative sugarcane juice medium, at 22 °Brix and pH 5.0, containing ethyl alcohol (99.5% PA) at concentrations of 0, 8 and 16% (v.v^-1). The flasks were kept at 250 rpm at temperatures of 30 and 40 °C. Samples were collected at 8 and 16 hours for analysis. Biomass production and cell viability decreased with increasing ethanol and fermentation time, especially the Fleischmann® strain, which showed greater sensitivity to stress than Pedra-2. High concentrations of ethanol and temperatures impaired yeast growth and viability. The study highlights the importance of selecting adaptable yeasts to improve the efficiency of industrial fermentation and the need for strategies to mitigate the negative effects of stress, ensuring the sustainability of ethanol production.

Keywords: Yeasts. Fermentation. Stress conditions. Bioethanol