New insights into the toxicity mechanism of octanoic and decanoic acids on Saccharomyces cerevisiae

Abstract

Octanoic (C8) and decanoic (C10) acids are produced in hypoxic conditions by the yeast Saccharomyces cerevisiae as by-products of its metabolism and are considered fermentation inhibitors in the presence of ethanol at acidic pH. This study aims to broaden our understanding of the physiological limits between toxicity and ester production in yeast cells. To this end, the non-inhibitory concentration (NIC) and maximum inhibitory concentration (MIC) values were first established for C8 and C10 at physiological pH (5.8) without ethanol. The results showed that when these acids were added to culture medium at these values, they tended to accumulate in different cellular fractions of the yeast. While C8 was almost entirely located in the cell wall fraction, C10 was found in the endocellular fraction. Cell fatty acid detoxification was also different; while the esterification of fatty acids was more efficient in the case of C10, the peroxisome was activated regardless of which fatty acid was added. Furthermore, the study of the Pdr12 and Tpo1 transporters that evolved during the detoxification process revealed that C8 was mostly expelled by the Pdr12 carrier, which was related to higher β-oxidative damage in the presence of endocellular C10. C10 is more toxic at lower concentrations than C8. Although they are produced by yeast, the resulting intracellular medium-chain fatty acids (MCFAs) caused a level of toxicity which promoted cell death. However, MCFAs are involved in the production of beverage flavours.

Engineering fungal de novo fatty acid synthesis for short chain fatty acid production

“…Regarding a putative impact on growth by toxic SCFAs3637, we were interested in clarifying whether a strong initial production of C 8 -FA accounts for the inhibition of further growth. Product spectra of selected strains were recorded after 12, 24 and 48 h; the latter constituting the regularly chosen measurement point.…”

Biotransformation of green tea (Camellia sinensis) by wine yeast Saccharomyces cerevisiae

“…All acids detected increased after fermentation. It was reported that yeasts are producers of octanoic and decanoic acids, which are by‐products of lipid synthesis during yeast fermentation (Borrull, López, Poblet, Cordero, & Rozès, ). This agrees with our results, from which octanoic acid increased significantly and decanoic acid was generated in the fermented tea.…”

Engineering Saccharomyces cerevisiae fatty acid composition for increased tolerance to octanoic acid

“…That no effect was observed for decanoic acid is likely a consequence of the different mechanisms that yeast employs to overcome octanoic and decanoic acids stress. While decanoic acid penetrates the cell and is esterified, octanoic acid remains in the membrane (Borrull et al, ; Legras et al, ). Interestingly, there was no improvement in ethanol resistance and significant drops in cell growth were observed at 24 and 36 h; this contrasts with prior reports in the literature at lower oleic acid levels (Yazawa et al, ; You et al, ; Zheng et al, ).…”

“…In prior work, octanoic aid was shown to increase membrane permeability due to its retention in the cell membrane (Borrull et al, 2015). Liu et al (2013) used magnesium leakage as a measure of membrane permeability.…”