During anaerobic fermentation, Saccharomyces cerevisiae releases large amounts of medium-chain fatty acids (MCFAs) and related ethyl esters which are very important for aromatic quality of fermented beverages. The physiological function of ester synthesis is not yet understood. As MCFAs are toxic, their conversion to esters has been proposed to be a detoxification mechanism. Esterases possess ester synthesizing ability. Throughout an anaerobic fermentation of a lipid-free synthetic medium carried out with a S. cerevisiae strain selected for wine making, we have monitored MCFA and ethyl ester production and, at the same time, measured growth and esterasic activity of intact cells. Because no correlation was found between the concentration of each fatty acid and its ethyl ester, there is no evidence that ester synthesis reduces the toxicity of MCFAs. Esterasic activity did not show any correlation with ester synthesis, but it was related to the release of MCFAs. A model is proposed in which ester synthesis is a consequence of the arrest of lipid biosynthesis resulting from a lack of oxygen. Under these conditions, an excess of acyl coenzyme A is produced, and acyl esters are formed as secondary products of reactions aimed at recovering free coenzyme A.
Nineteen substituted 2‐phenylbenz‐X‐azoles, which are intermediates for the synthesis of dyes, were prepared from p‐aminosalicylic acid (PAS). Substituents in the phenyl ring are 2′‐hydroxy and/or 4′‐amino and 4′‐alkylamido with alkyl chains ranging from C1 to C15. The preferred route of the synthesis is discussed. The melting points and the Rf values are correlated with the structure. An extensive discussion of the electronic absorption spectra, involving other compounds with the same general structure, is reported.
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