Mechanisms underlying the transport and intracellular metabolism of acetic acid in the presence of glucose in the yeast Zygosaccharomyces bailii

Abstract

Zygosaccharomyces bailii ISA 1307 displays biphasic growth in a medium containing a mixture of glucose (0*5%, whr) and acetic acid (05Y0, whr), pH 5 9 and 39. In cells harvested during the first growth phase, no activity of a mediated acetic acid transport system was found. Incubation of these cells in phosphate buffer with cycloheximide for 1 h restored activity of an acetic acid carrier which behaved as the one present in glucose-grown cells. These results indicated that the acetic acid carrier is probably present in cells from the first growth phase of the mixed medium but its activity was affected by the presence of acetic acid in the culture medium. In glucose-grown cells, after incubation in phosphate buffer with glucose and acetic acid, the activity of the acetic acid carrier decreased significantly with increased acid concentration in the incubation buffer. A t acid concentrations above 1 6 7 mM, no significant carrier activity was detectable. Furthermore, the intracellular acid concentration increased with the extracellular one and was inversely correlated with the activity of the acetic acid carrier, suggesting the involvement of a feedback inhibition mechanism in the regulation of the carrier. During biphasic growth, the first phase corresponded to a simultaneous consumption of glucose and acetic acid, and the second to the utilization of the remaining acid. The enzyme acetyl-CoA synthetase was active in both growth phases, even in the presence of glucose. Activity of isocitrate lyase and phosphoenolpyruvate carboxykinase was found only in acetic-acidgrown cells. Thus it appears that both membrane transport and acetyl-CoA synthetase and their regulation are important for 2. bailii to metabolize acetic acid in the presence of glucose. This fact correlates with the high resistance of this yeast to environments with mixtures of sugars and acetic acid such as those often present during wine fermentation.

Novel stress responses facilitate Saccharomyces cerevisiae growth in the presence of the monocarboxylate preservatives

“…The highly preservative-resistant Z. bailii is able to catalyse oxidative degradation of sorbate and benzoate, [17,18] as well as assimilate acetate whilst growing on glucose. [31] Its capacity for sorbate and benzoate degradation originates from a mitochondrial monooxygenase with benzoate-4-hydroxylase activity, an enzyme with a carboxylate-linked diiron centre that -at least when expressed heterologously in S. cerevisiae -derives its reducing power from the mitochondrial electron transport chain. In the presence of oxygen, this activity elevates the sorbate and benzoate resistances of Z. bailii by facilitating the degradation of these preservatives.…”

Weak acid adaptation: the stress response that confers yeasts with resistance to organic acid food preservatives

“…The latter yeasts can sometimes grow in the presence of the highest levels of those acids allowed in food preservation, at pH values below the pK a values of these acids (Thomas & Davenport, 1985 ;Deak, 1991 ;Fleet, 1992 ;Steels et al, 1999Steels et al, , 2000. Z. bailii has also attracted attention as a spoilage agent of wine, a property that accrues from its high ethanol tolerance (Kalathenos et al, 1995) and ability to metabolize acetic acid in the presence of the complex mixtures of sugars often found in wine fermentations (Sousa et al, 1996(Sousa et al, , 1998.…”

“…Apart from a number of studies on the uptake and utilization of acetate by Z. bailii (Sousa et al, 1996(Sousa et al, , 1998, comparatively little is known about how Z. bailii and Z. lentus acquire their remarkable weak acid resistances. Considerably more is known about weak acid adaptation in S. cerevisiae, as this is a species amenable to genetic analysis.…”

Stress and Cell Death in Yeast Induced by Acetic Acid

“…Additionally, in the presence of glucose, Z. bailii displays a reduced passive permeability to the acid when compared with S. cerevisiae (Sousa et al, 1996). Unlike most strains of S. cerevisiae, which are unable to metabolize acetic acid in the presence of glucose, Z. bailii is able to simultaneous use the two substrates due to the high activity of the enzyme acetyl-CoA synthetase (Sousa et al, 1998). Thus, it appears that in Z. bailii both membrane transport and acetyl-CoA synthetase could assume particular physiological relevance in regards to the high resistance of this yeast species to environments containing mixtures of sugars and acetic acid, such as those often present during wine fermentation.…”