Comparison of the inhibitory action on<i>Saccharomyces cerevisiae</i>of weak-acid preservatives, uncouplers, and medium-chain fatty acids

Stratford, Malcolm; Anslow, P.A.

doi:10.1111/j.1574-6968.1996.tb08407.x

Cited by 73 publications

(16 citation statements)

References 10 publications

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“…Indeed, we show that these two enzymes are involved in the esterification of MCFAs, which are toxic compounds for yeast (24). Hence Eht1 and Eeb1 could thus be involved in their detoxification by esterification.…”

Section: S Cerevisiae May Contain Additional Medium-chain Fatty Acidmentioning

confidence: 72%

The Saccharomyces cerevisiae EHT1 and EEB1 Genes Encode Novel Enzymes with Medium-chain Fatty Acid Ethyl Ester Synthesis and Hydrolysis Capacity

Saerens

Verstrepen

Laere

et al. 2006

Journal of Biological Chemistry

268

311

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Fatty acid ethyl esters are secondary metabolites produced bySaccharomyces cerevisiae and many other fungi. Their natural physiological role is not known but in fermentations of alcoholic beverages and other food products they play a key role as flavor compounds. Information about the metabolic pathways and enzymology of fatty acid ethyl ester biosynthesis, however, is very limited. In this work, we have investigated the role of a three-member S. cerevisiae gene family with moderately divergent sequences (YBR177c/EHT1, YPL095c/EEB1, and YMR210w). We demonstrate that two family members encode an acyl-coenzymeA:ethanol O-acyltransferase, an enzyme required for the synthesis of mediumchain fatty acid ethyl esters. Deletion of either one or both of these genes resulted in severely reduced medium-chain fatty acid ethyl ester production. Purified glutathione S-transferase-tagged Eht1 and Eeb1 proteins both exhibited acyl-coenzymeA:ethanol O-acyltransferase activity in vitro, as well as esterase activity. Overexpression of Eht1 and Eeb1 did not enhance medium-chain fatty acid ethyl ester content, which is probably due to the bifunctional synthesis and hydrolysis activity. Molecular modeling of Eht1 and Eeb1 revealed the presence of a ␣/␤-hydrolase fold, which is generally present in the substrate-binding site of esterase enzymes. Hence, our results identify Eht1 and Eeb1 as novel acyl-coenzymeA:ethanol O-acyltransferases/esterases, whereas the third family member, Ymr210w, does not seem to play an important role in mediumchain fatty acid ethyl ester formation.The synthesis of fatty acid ethyl esters (FAEEs) 3 is widely distributed in microorganisms, higher plants, and mammals. In mammals, FAEEs are the result of the nonoxidative pathway for the metabolism of ethanol, after ethanol intake (1, 2). In higher plants and microorganisms, FAEEs are formed as secondary metabolites. Because of their strong fruit flavor, ethyl esters of short-and medium-chain fatty acids (MCFAs) constitute a large group of flavor compounds particularly important in the food, beverage, cosmetic, and pharmaceutical industries. The biosynthesis of FAEEs proceeds by two different enzymatic mechanisms, esterification or alcoholysis (3). Esterification is the formation of esters from alcohols and carboxylic acids and is catalyzed by FAEE synthases/carboxylesterases. Alcoholysis is the production of esters from alcohols and acylglycerols or from alcohols and fatty acylCoAs derived from metabolism of fatty acids. Alcoholysis is essentially a transferase reaction in which fatty acyl groups from acylglycerols or acyl-CoA derivatives are directly transferred to alcohols. The formation of FAEEs by alcoholysis is catalyzed by acyl-CoA:ethanol O-acyltransferases (AEATases) (4).Ester biosynthesis is very common in microorganisms, especially in bacteria and yeasts that are used in the fermentation of alcoholic beverages and food products. Information about the metabolic pathways and enzymology of ester biosynthesis in these microorganisms, however, is still v...

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Section: S Cerevisiae May Contain Additional Medium-chain Fatty Acidmentioning

confidence: 72%

The Saccharomyces cerevisiae EHT1 and EEB1 Genes Encode Novel Enzymes with Medium-chain Fatty Acid Ethyl Ester Synthesis and Hydrolysis Capacity

Saerens

Verstrepen

Laere

et al. 2006

Journal of Biological Chemistry

268

311

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“…The latter is corroborated by the greater effect that sorbic acid has on the membrane potential, while acetic acid carries only bulk volume protons across the membrane until a steady state is reached, allowing ⌬ to remain relatively unaffected. Even though some authors have pointed to the similar effects of the uncoupler 2,4-dinitrophenol and sorbic acid on growth and metabolism (9,33,34), to our knowledge no quantitative measurements of the effect that sorbic acid has on ⌬ have been reported thus far. While relatively little research on the effects that WOA preservatives have on the membrane potential of microorganisms has been published (6,16,29,35,36), the depletion of ⌬ may have a plethora of effects.…”

Section: Discussionmentioning

confidence: 94%

Distinct Effects of Sorbic Acid and Acetic Acid on the Electrophysiology and Metabolism of Bacillus subtilis

Beilen

Mattos

Hellingwerf

et al. 2014

Appl Environ Microbiol

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b Sorbic acid and acetic acid are among the weak organic acid preservatives most commonly used to improve the microbiological stability of foods. They have similar pK a values, but sorbic acid is a far more potent preservative. Weak organic acids are most effective at low pH. Under these circumstances, they are assumed to diffuse across the membrane as neutral undissociated acids. We show here that the level of initial intracellular acidification depends on the concentration of undissociated acid and less on the nature of the acid. Recovery of the internal pH depends on the presence of an energy source, but acidification of the cytosol causes a decrease in glucose flux. Furthermore, sorbic acid is a more potent uncoupler of the membrane potential than acetic acid. Together these effects may also slow the rate of ATP synthesis significantly and may thus (partially) explain sorbic acid's effectiveness.

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“…A comparative study of inhibition by a weak acid (sorbic acid), an uncoupler (2,4-dinitrophenol) and a carboxylic acid (decanoic acid) observed that the carboxylic acid caused rapid cell death relative to the other two inhibitors and concluded that the mechanism of inhibition by carboxylic acids must be distinct from the other two molecule types (Stratford and Anslow, 1996). Desbois and Smith (2010) briefly review the association of molecule structure and shape with its potency as an inhibitor, but since most of these relationships deal with unsaturated molecules they are not discussed here.…”

Section: Characterization Of Inhibition As a Function Of Molecule Strmentioning

confidence: 99%

Understanding biocatalyst inhibition by carboxylic acids

Jarboe¹,

Royce²,

Liu³

2013

Front. Microbiol.

118

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Carboxylic acids are an attractive biorenewable chemical in terms of their flexibility and usage as precursors for a variety of industrial chemicals. It has been demonstrated that such carboxylic acids can be fermentatively produced using engineered microbes, such as Escherichia coli and Saccharomyces cerevisiae. However, like many other attractive biorenewable fuels and chemicals, carboxylic acids become inhibitory to these microbes at concentrations below the desired yield and titer. In fact, their potency as microbial inhibitors is highlighted by the fact that many of these carboxylic acids are routinely used as food preservatives. This review highlights the current knowledge regarding the impact that saturated, straight-chain carboxylic acids, such as hexanoic, octanoic, decanoic, and lauric acids can have on E. coli and S. cerevisiae, with the goal of identifying metabolic engineering strategies to increase robustness. Key effects of these carboxylic acids include damage to the cell membrane and a decrease of the microbial internal pH. Certain changes in cell membrane properties, such as composition, fluidity, integrity, and hydrophobicity, and intracellular pH are often associated with increased tolerance. The availability of appropriate exporters, such as Pdr12, can also increase tolerance. The effect on metabolic processes, such as maintaining appropriate respiratory function, regulation of Lrp activity and inhibition of production of key metabolites such as methionine, are also considered. Understanding the mechanisms of biocatalyst inhibition by these desirable products can aid in the engineering of robust strains with improved industrial performance.

show abstract

Comparison of the inhibitory action onSaccharomyces cerevisiaeof weak-acid preservatives, uncouplers, and medium-chain fatty acids

Cited by 73 publications

References 10 publications

The Saccharomyces cerevisiae EHT1 and EEB1 Genes Encode Novel Enzymes with Medium-chain Fatty Acid Ethyl Ester Synthesis and Hydrolysis Capacity

The Saccharomyces cerevisiae EHT1 and EEB1 Genes Encode Novel Enzymes with Medium-chain Fatty Acid Ethyl Ester Synthesis and Hydrolysis Capacity

Distinct Effects of Sorbic Acid and Acetic Acid on the Electrophysiology and Metabolism of Bacillus subtilis

Understanding biocatalyst inhibition by carboxylic acids

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