Benzoic Acid, a Weak Organic Acid Food Preservative, Exerts Specific Effects on Intracellular Membrane Trafficking Pathways in Saccharomyces cerevisiae

Abstract

Microbial spoilage of food causes losses of up to 40% of all food grown for human consumption worldwide. Yeast growth is a major factor in the spoilage of foods and beverages that are characterized by a high sugar content, low pH, and low water activity, and it is a significant economic problem. While growth of spoilage yeasts such as Zygosaccharomyces bailii and Saccharomyces cerevisiae can usually be retarded by weak organic acid preservatives, the inhibition often requires levels of preservative that are near or greater than the legal limits. We identified a novel synergistic effect of the chemical preservative benzoic acid and nitrogen starvation: while exposure of S. cerevisiae to either benzoic acid or nitrogen starvation is cytostatic under our conditions, the combination of the two treatments is cytocidal and can therefore be used beneficially in food preservation. In yeast, as in all eukaryotic organisms, survival under nitrogen starvation conditions requires a cellular response called macroautophagy. During macroautophagy, cytosolic material is sequestered by intracellular membranes. This material is then targeted for lysosomal degradation and recycled into molecular building blocks, such as amino acids and nucleotides. Macroautophagy is thought to allow cellular physiology to continue in the absence of external resources. Our analyses of the effects of benzoic acid on intracellular membrane trafficking revealed that there was specific inhibition of macroautophagy. The data suggest that the synergism between nitrogen starvation and benzoic acid is the result of inhibition of macroautophagy by benzoic acid and that a mechanistic understanding of this inhibition should be beneficial in the development of novel food preservation technologies.

Alcoholic fermentation of carbon sources in biomass hydrolysates by Saccharomyces cerevisiae: current status

“…In addition, intracellular accumulation of the anion, either by itself or in combination with intracellular acidification, can lead to toxic effects (Casal et al 1996;Eklund 1983;Pampulha and Loureiro-Dias 1990;Russell 1992). Benzoate, for instance, has been implicated in inhibition of autophagy (Hazan et al 2004) and acetate has been demonstrated to induce apoptosis (Ludovico et al 2001). Moreover, hydrolysates contain many compounds that act synergistically with organic acids.…”

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

“…[1,19,36] Therefore, while acetic acid may largely inhibit cells by generating a high intracellular pool of acetate anion and the lowering of intracellular pH (Figure 1b), the cytostatic effects of sorbic acid are suggested to be mainly due to its disordering of membrane structure. [2,36] High acetic acid is a potent inducer of yeast apoptosis; [6,[14][15][16] whereas the noted actions of benzoic and sorbic acids include a severe energy (ATP pool) depletion, [26] an inhibition of membrane trafficking, resulting in the arrest of macroautophagy [8] and, in the presence of oxygen, severe oxidative stress due to elevated endogenous production of reactive oxygen species (ROS) by a dysfunctional mitochondrial respiratory chain. [25] It is now known that acetic acid and sorbic acid, at these respective inhibitory concentrations, induce quite separate stress responses in pH 4.5 cultures of S. cerevisiae; one protective against acetic acid stress and another protective against the more lipophilic propionate, sorbate and benzoate (Table 1).…”

Quantification of Geotrichum candidum growth in co-culture with lactic acid bacteria

“…Yeasts are able to reduce the accumulation of weak acids inside the cells. The mechanisms of weak acid adaptation in yeasts are described in the studies of Brul and Coote (1999), Piper et al (2001), Hazan et al (2004).…”