Relationship between proton/ potassium fluxes and central carbon catabolic pathways in different Saccharomyces cerevisiae strains under osmotic stress conditions

Ion homeostasis is pivotal for numerous cellular functions and adaptation. Investigation of the relationship between K+ and H+ transporters and energy exchange processes of S. cerevisiae ATCC 9804 and ATCC 13007 strains will be crucial to enhance resistance to osmotic stress and improve industrial processes. Specific growth rate (SGR), pH and oxidation-reduction potential (ORP), K+ and H+ fluxes, mitochondrial H+-ATPase activity changes, and metabolites were studied in physiological and osmotic stress conditions. Strictly neutral conditions are needed for yeast biomass production under osmotic stress (microaerophilic growth), where the SGR of ATCC 9804 is suppressed-85% and in ATCC 13007-60% compared to physiological conditions. The addition of N ' N'- dicyclohexylcarbodiimide (DCCD) completely abolishes K+ and H+ transport. High affinity to K+ ions were registered in aerobic growth, which decreased during the transition to microaerophilic growth, as well as under stress, and was especially low in DCCD-inhibited samples. Mitochondrial H+-ATPase activity was suppressed -5-fold under osmotic stress conditions, compared with the physiological one. Taken together it can be concluded that cell membrane transporters and the mitochondrial proton-potassium exchange systems, are crucial in maintaining cell physiological functions, regulating the energy balance via FOF1-ATPase, as well as in stress responding processes.