The Yeast Vacuole -A Scanning Electron Microscopy Study During High Gravity Wort Fermentations

Pratt, Patricia L.; Bryce, James H.; Stewart, Graham G.

doi:10.1002/j.2050-0416.2007.tb00256.x

Cited by 16 publications

(18 citation statements)

References 13 publications

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“…). This early accumulation of trehalose is typical during brewing fermentations (Pratt et al ., ) and is more pronounced in higher gravity worts (Majara et al ., ; Reinman & Londesborough, ), suggesting it may be related to hyperosmotic stress. The variant A218 also accumulated less glycogen than did A15.…”

Section: Discussionmentioning

confidence: 99%

Adaptive evolution of the lager brewing yeastSaccharomyces pastorianusfor improved growth under hyperosmotic conditions and its influence on fermentation performance

Ekberg

Rautio²,

Mattinen³

et al. 2013

FEMS Yeast Res

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An adaptive evolution method to obtain stable Saccharomyces pastorianus brewing yeast variants with improved fermentation capacity is described. The procedure involved selection for rapid growth resumption at high osmotic strength. It was applied to a lager strain and to a previously isolated ethanol-tolerant strain. Fermentation performance of strains was compared at 15 °P wort strength. A selected osmotolerant variant of the ethanol-tolerant strain showed significantly shorter fermentation time than the parent strain, producing 6.45% alcohol by volume beer in 4-5 days with mostly similar organoleptic properties to the original strain. Diacetyl and pentanedione contents were 50-75% and 3-methylbutyl acetate and 2-phenylethyl acetate 50% higher than with the original strain, leading to a small flavour change. The variant contained significantly less intracellular trehalose and glycogen than the parent. Transcriptional analysis of selected genes at 24 h revealed reduced transcription of hexose transport genes and increased transcription of the MALx1 and MALx2 genes, responsible for α-glucoside uptake and metabolism. It is suggested that an attenuated stress response contributes to the improved fermentation performance. Results show that sequential selection for both ethanol tolerance and rapid growth at high osmotic strength can provide strains with enhanced fermentation speed with acceptable product quality.

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Section: Discussionmentioning

confidence: 99%

Adaptive evolution of the lager brewing yeastSaccharomyces pastorianusfor improved growth under hyperosmotic conditions and its influence on fermentation performance

Ekberg

Rautio²,

Mattinen³

et al. 2013

FEMS Yeast Res

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“…Sterile all-malt hopped very high gravity wort (23 5,21 . Fermentation was carried out by the yeasts FBY0095 and FBY0095-05 respectively in 7 L pilot fermenters with 5 L of sterile wort medium in each fermenter at a temperature of 12°C.…”

Section: Wort Preparation and Fermentationmentioning

confidence: 99%

The Dynamic Changes of Proton Efflux Rate in Saccharomyces pastorianus Strains During High Gravity or Very High Gravity Brewing

Zhang

Zhao

Wan

et al. 2011

Journal of the Institute of Brewing

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The changes in the proton efflux rate (PER) during fermentation of normal gravity (NG), high gravity (HG) and very high gravity (VHG) wort by a lager yeast (Saccharomyces pastorianus) were monitored using an optimized PER test method. The values of the proton efflux rate in S. pastorianus decreased with increasing initial wort gravity. Moreover, the difference in the proton efflux rate values at the beginning of the fermentation was lower than at the end of fermentation from normal gravity to very high gravity brewing. These results demonstrated that the proton efflux rate in S. pastorianus was inhibited in the later stages of high gravity and very high gravity brewing. Furthermore, the changes of the proton efflux rate in S. pastorianus under the high ethanol concentration conditions appeared to depend on the concentration of ethanol in the fermentation liquid. A better negative correlation (P < 0.001, r = -0.95) between the ethanol concentration at >4% (w/v) and the proton efflux rate was found. The changes of the proton efflux rate in the cells treated with exogenous ethanol confirmed that higher concentrations of ethanol could significantly inhibit proton efflux in S. pastorianus. This study offers a possible way to monitor and explain the performance of yeast in the complex environment of high gravity and very high gravity brewing.

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“…Yeast cells modify their vacuolar volume by increasing in size during the fermentation of 20°Plato wort compared to the same yeast strain fermenting 12°Plato wort (Figs. 33 and 34) 98 . As well as changes in vacuolar size, high gravity wort modifies the cell surface morphology of a yeast culture (Fig.…”

Section: Yeast Morphological Changes Induced By High Gravity Wortsmentioning

confidence: 97%

“…Viewed with a scanning electron microscope, cells fermenting a 20°Plato wort had a very uneven cell surface topology compared to cells fermenting a 12°Plato wort. Those fermenting the low gravity wort exhibited a much smoother surface structure 98 .…”

Section: Yeast Morphological Changes Induced By High Gravity Wortsmentioning

confidence: 99%

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The Horace Brown Medal Lecture: Forty Years of Brewing Research

Stewart

2009

Journal of the Institute of Brewing

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Horace Brown spent fifty years conducting brewing research in Burton-on-Trent, Dublin and London. His contributions were remarkable and his focus was to solve practical brewing problems by employing and developing fundamental scientific principles. He studied all aspects of the brewing process including raw materials, wort preparation, fermentation, yeast and beer stability. As a number of previous presenters of the Horace Brown Lecture have discussed Brown's achievements in detail, the focus of this paper is a review of the brewing research that has been conducted by the author and his colleagues during the past forty years. Similar to Horace Brown, fundamental research has been employed to solve brewing problems. Research studies that are discussed in this review paper include reasons for premature flocculation of ale strains resulting in wort underattenuation including mechanisms of co-flocculation and pure strain flocculation, storage procedures for yeast cultures prior to propagation, studies on the genetic manipulation of brewer's yeast strains with an emphasis on the FLO1 gene, spheroplast fusion and the respiratory deficient (petite) mutation, the uptake and metabolism of wort sugars and amino acids, the influence of wort density on fermentation characteristics and beer flavour and stability, and finally, the contribution that high gravity brewing has on brewing capacity, fermentation efficiency and beer quality and stability.

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The Yeast Vacuole -A Scanning Electron Microscopy Study During High Gravity Wort Fermentations

Cited by 16 publications

References 13 publications

Adaptive evolution of the lager brewing yeastSaccharomyces pastorianusfor improved growth under hyperosmotic conditions and its influence on fermentation performance

Adaptive evolution of the lager brewing yeastSaccharomyces pastorianusfor improved growth under hyperosmotic conditions and its influence on fermentation performance

The Dynamic Changes of Proton Efflux Rate in Saccharomyces pastorianus Strains During High Gravity or Very High Gravity Brewing

The Horace Brown Medal Lecture: Forty Years of Brewing Research

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