The Effect of Osmotic Pressure on the Production and Excretion of Ethanol and Glycerol by a Brewing Yeast Strain*

Panchal, Chandra J.; Stewart, Graham G.

doi:10.1002/j.2050-0416.1980.tb06867.x

Cited by 93 publications

(57 citation statements)

References 7 publications

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“…A number of recent reports suggest that the concentration of ethanol within fermenting yeast cells may be many times higher than the extracellular ethanol concentration (Nagodawithana and Steinkraus, 1976;Navarro and Durand, 1978;Thomas and Rose, 1979;Panchal and Stewart, 1980;Navarro, 1980;Novak et al, 1981;Rose and Beaven, 1981;Goma et al, 1981;Beaven et al, 1982;Navarro and Finck, 1982;Pamment and Stucley, 1982;Stucley and PanTnent, 1982;Strehaiano and Goma, 1983). The implication of these findings is that, under certain conditions, the rate of ethanol production within cells exceeds the rate at which it can be transferred to the surrounding medium.…”

Section: Introductionmentioning

confidence: 98%

Factors affecting the estimation of intracellular ethanol concentrations

et al. 1983

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SUMMARY Estimates of intracellular ethanol concentration in batch culturesof Saooharomyoes cerevisiae were significantly affected by continued fermentation during processing of the sample. Precooling of samples to 4°C and reduction of centrifugation time significantly reduced apparent intracellular ethanol concentration.Intracellular ethanol concentrations were substantially lower than in some previous reports and fell below the extracellular ethanol concentrations during the later stages of fermentation. I NTRODUCTI ONA number of recent reports suggest that the concentration of ethanol within fermenting yeast cells may be many times higher than the extracellular ethanol concentration

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Section: Introductionmentioning

confidence: 98%

Factors affecting the estimation of intracellular ethanol concentrations

et al. 1983

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“…The frequent sluggish or stuck fermentations encountered in high-gravity brewing are probably caused by several stress factors that are not present or are at least less pronounced compared to traditional brewing results (19,21,29,30). In particular, the high osmolarity at the beginning of the fermentation and the high ethanol content combined with nutrient starvation at the end of the fermentation are thought to be the major culprits.…”

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confidence: 99%

Isolation and Characterization of Brewer's Yeast Variants with Improved Fermentation Performance under High-Gravity Conditions

Blieck

Toye

Dumortier

et al. 2007

Appl Environ Microbiol

105

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To save energy, space, and time, today's breweries make use of high-gravity brewing in which concentrated medium (wort) is fermented, resulting in a product with higher ethanol content. After fermentation, the product is diluted to obtain beer with the desired alcohol content. While economically desirable, the use of wort with an even higher sugar concentration is limited by the inability of brewer's yeast (Saccharomyces pastorianus) to efficiently ferment such concentrated medium. Here, we describe a successful strategy to obtain yeast variants with significantly improved fermentation capacity under high-gravity conditions. We isolated betterperforming variants of the industrial lager strain CMBS33 by subjecting a pool of UV-induced variants to consecutive rounds of fermentation in very-high-gravity wort (>22°Plato). Two variants (GT336 and GT344) showing faster fermentation rates and/or more-complete attenuation as well as improved viability under high ethanol conditions were identified. The variants displayed the same advantages in a pilot-scale stirred fermenter under high-gravity conditions at 11°C. Microarray analysis identified several genes whose altered expression may be responsible for the superior performance of the variants. The role of some of these candidate genes was confirmed by genetic transformation. Our study shows that proper selection conditions allow the isolation of variants of commercial brewer's yeast with superior fermentation characteristics. Moreover, it is the first study to identify genes that affect fermentation performance under high-gravity conditions. The results are of interest to the beer and bioethanol industries, where the use of more-concentrated medium is economically advantageous.Today's need to produce quality beers in a short time and in the least-expensive way has led most breweries to switch to high-gravity brewing. Traditionally, brewing worts of 12°Plato (12°P) (i.e., 12 g extract per 100 g liquid) are fermented to produce beers of 5% (vol/vol) ethanol. However, substantial cost savings can be realized by increasing the wort density (called "gravity") from 12°P to 18°P and diluting the 7.5% (vol/vol) ethanol-containing product in order to obtain beer with regular ethanol content (5%). The use of this technology increases the brewery capacity by 50% (for 18°P wort) without the need for any investments, reduces the costs in energy and labor (because liquid volumes are reduced), improves the stability of the beer, and enhances the recovery of ethanol per unit of fermentable sugar ("extract") (15, 44). However, the technology is limited by the stress resistance and fermentation performance of the brewer's lager yeast Saccharomyces pastorianus. S. cerevisiae (used for ale and wine fermentations) can cope much better with such stress conditions. Wine must typically contains up to 25% (wt/wt) sugar, but a major difference from beer production is that the yeast is only used once in wine fermentation whereas it is used multiple times in beer fermentation. In addition, wine m...

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“…13 Because no base and less sulfuric acid are used, salt buildup is minimized, and yeast cells are not inhibited as soon from increased osmotic pressure. 16 Few adverse effects on the conversion of starch to glucose resulted from liquefaction with a reduced amount of water (Table I). However, 40% recycling is near the maximum permissible level due to the high viscosity of liquefied mash at that level of recycling (mixing and pumping difficult).…”

Section: Stillage Supernatant Recyclingmentioning

confidence: 99%

Fuel ethanol and high protein feed from corn and corn–whey mixtures in a farm‐scale plant

Gibbons

Westby

1983

Biotech & Bioengineering

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Distiller's wet grain (DWG) and 95% ethanol were produced from corn in a farm-scale process involving batch cooking-fermentation and continuous distillation-centrifugation. The energy balance was 2.26 and the cost was $1.86/gal (1981 cost). To improve the energy balance and reduce costs, various modifications were made in the plant. The first change, back-end (after liquefaction) serial recycling of stillage supernatant at 20 and 40% strengths, produced beers with 0.2 and 0.4% (v/v) more ethanol, respectively, than without recycling. This increased the energy balance by 0.22-0.43 units and reduced costs by $0.07-$0.10/gal. The DWGs from back-end recycling had increased fat. The second change, increasing the starch content from 17-19% to 27.5%, increased the ethanol in the beer from 10.5-14.9% at a cost saving of $0.41/gal. The energy balance increased by 1.08 units. No significant change was seen in DWG composition. The third change, using continuous cascade rather than batch fermentation, permitted batch-levels of ethanol (10%) in the beer but only at low dilution rates. Both the cost and energy balance were decreased slightly. The DWG composition remained constant. The last change, replacing part of the corn and all of the tap water in the mash with whole whey and using Kluyveromyces fragilis instead of Saccharomyces cerevisiae during fermentation, resulted in an energy balance increase of 0.16 units and a $0.27/gal cost reduction. Here, 10% ethanolic beers were produced and the DWGs showed increased protein and fat. Recommendations for farm-scale plants are provided.

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The Effect of Osmotic Pressure on the Production and Excretion of Ethanol and Glycerol by a Brewing Yeast Strain*

Cited by 93 publications

References 7 publications

Factors affecting the estimation of intracellular ethanol concentrations

Factors affecting the estimation of intracellular ethanol concentrations

Isolation and Characterization of Brewer's Yeast Variants with Improved Fermentation Performance under High-Gravity Conditions

Fuel ethanol and high protein feed from corn and corn–whey mixtures in a farm‐scale plant

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