Analysis and enhancement of the ethanol resistance of Pichia kudriavzevii N77-4, a strain newly isolated from the Korean traditional fermentation starter Nuruk, for improved fermentation performance

Adaptive responses of Kluyveromyces marxianus CCT 7735 to 2-phenylethanol stress: Alterations in membrane fatty-acid composition, ergosterol content, exopolysaccharide production and reduction in reactive oxygen species

2-phenylethanol (2-PE) is a higher aromatic alcohol with a rose-like aroma used in the cosmetic and food industries as a flavoring and displays potential for application as an antifungal. Biotechnological production of 2-PE from yeast is an interesting alternative due to the non-use of toxic compounds and the generation of few by-products. Kluyveromyces marxianus CCT 7735 is a thermotolerant strain capable of producing high 2-PE titers from L-Phenylalanine; however, like other yeast species, its growth has been strongly inhibited by this alcohol. Herein, we aimed to evaluate the effect of 2-PE on cell growth, cell viability, membrane permeability, glucose uptake, metabolism, and morphology in K. marxianus CCT 7735, as well as its adaptive responses. The stress condition was imposed after 4 h of cultivation by adding 3.0 g.L^-1 of 2-PE in exponential growing cells. 2-PE stress impaired yeast growth, glucose uptake, fermentative metabolism, membrane permeability, and cell viability. Moreover, the stress condition provoked changes in both morphology and surface roughness. The reactive oxygen species (ROS) increased immediately on exposure to 2-PE. Changes in membrane fatty-acid composition, ergosterol content, exopolysaccharides production, and reduction of the ROS levels appear to be the result of adaptive responses in K. marxianus. Our results provided insights into a better understanding of the effects of 2-PE on K. marxianus and its adaptive responses.