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Yeast: Difference between revisions
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Maltose(100 g) + aminoacids(0.5 g) → yeast(5 g) + ethanol(48.8 g) + CO | Maltose(100 g) + aminoacids(0.5 g) → yeast(5 g) + ethanol(48.8 g) + CO | ||
2 (46.8 g) + energy(50 kcal)<ref>https://www.academia.edu/30908633/Process_modelling_and_technology_evaluation_in_brewing</ref> | 2 (46.8 g) + energy(50 kcal)<ref>https://www.academia.edu/30908633/Process_modelling_and_technology_evaluation_in_brewing</ref> | ||
The ability to produce high concentrations of ethanol without permanently damaging yeast cells and compromising fermentation performance is particularly important in brewing, as yeast populations are normally required to ferment multiple brews in succession192. While ethanol toxicity has been ascribed to non-specific effects on the cell48,103, the weight of evidence suggests that membranes are the main targets of ethanol toxicity. It has been suggested that the effect of ethanol on membranes is due to its insertion into the hydrophobic interior and the resultant effects on polarity, exchange of polar molecules and the position of membrane proteins91. Direct ethanol exposure results in increased fluidity of membranes103,127,145 and increased membrane permeability causing leakage of amino acids, leakage of compounds absorbing light at 260 nm and leakage of proteases75,91,146,182 and influx of protons99,117,120. The cellular membrane is not, however, the only target for ethanol toxicity and the mitochondrial membrane may also suffer damage, leading directly or indirectly to mitochondrial DNA damage and the generation of respiratory deficient (petite) strains40,75,99. Indeed, serial repitching of yeast in breweries has been associated with an increase in the frequency of petite mutants, probably caused by repeated exposure to potentially toxic levels of ethanol during fermentation and storage98<ref name=gib125>Gibson BR. [https://onlinelibrary.wiley.com/doi/pdf/10.1002/j.2050-0416.2011.tb00472.x 125th anniversary review: improvement of higher gravity brewery fermentation via wort enrichment and supplementation.] ''J Inst Brew.'' 2011;117(3):268–284.</ref> | |||
== Articles to be reviewed == | == Articles to be reviewed == | ||