Effects of Fermentation Environment on Yeast Lipid Synthesis

Abstract

The goal of the present investigation was to study the influence of various brewing parameters on the total lipid content as well as the fatty acid composition of the yeast. The effects of fermentation temperature, aerobic vs. anaerobic growth, yeast strain, and adjunct level were explored. The results revealed that yeast contained more lipids and more unsaturated fatty acids when grown at lower temperatures. Aerobic growth conditions increased the amount of unsaturated acids and sterols. The fatty acid composition of three yeast strains displayed some differences when grown under identical conditions and the total lipid content rose markedly when increasing portions of corn syrup were used for wort production. In an effort to determine the site of these lipid changes, yeast cells were homogenized and subjected to a differential centrifugation. Three different subcellular particles were obtained and analyzed for lipids. An attempt was made to correlate some of these findings with the accumulation of ethyl acetate in the resultant beer.

Processing of a Top Fermented Beer Brewed from 100% Buckwheat Malt with Sensory and Analytical Characterisation

“…One explanation for this may be to a high wort glucose concentration. It has been found that catabolite repression was observed in yeast cells when grown in media containing 5% glucose and resulted in the acetylCoA molecules directed more toward lipid synthesis than to ester formation 53 .…”

Utilization of Wort Fatty Acids by Yeast during Fermentation

“…The effect of long-chain wort fatty acids on the formation of medium-chain beer fatty acids is similar, although different in magnitude and mechanism, to that of growth factors such as biotin and minerals (5). The combined influence of other factors, eg, fermentation environment (11), may accentuate the relationship.…”

Relationship Between Fatty Acid Concentrations in Wine Yeasts and Sugar Fermentation at Different Temperatures

“…Lower growth temperatures for example increase the proportion of unsaturated lipids in yeast cells (Pfisterer, Hancock & Garrison, 1977). However, according to McMurrough & Rose (1971), temperature variation does not significantly alter the fatty acid composition of the early exponential phase cells, but profoundly affects the synthesis of these compounds during the later exponential phase.…”

“…The nature of the fatty acids (incorporated into phospholipids) affects the functions of certain proteins in the membrane (Pfisterer et al, 1977). The functional role of lipids, their fatty acid composition and degree ofunsaturation, are regarded as major factors in the transport effects of membranes and the realization of fermentative activities in micro-organisms (Sinensky, 1971).…”