Effects of the kinetics of osmotic pressure variation on yeast viability

Gervais, Patrick; Marechal, Pierre-André; Molin, Paul

doi:10.1002/bit.260401119

Cited by 59 publications

(28 citation statements)

References 15 publications

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“…These findings indicated that there could be a relationship between temperature and cell viability under hyperosmotic stresses 2 as this study was performed at 21°C. Additionally, the ability of the ale strains to maintain high viabilities may be in agreement with Gervais et al 18 and Marañon et al 26 . Both groups postulated that the ability of a yeast strain to support a higher gradient of osmotic pressure could be due to turgor pressure and thickness of the cell membrane.…”

Section: (-7'977-32supporting

confidence: 87%

The Effects of Osmotic Pressure and Ethanol on Yeast Viability and Morphology

Pratt

Bryce

Stewart

2003

Journal of the Institute of Brewing

104

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The selection of a brewing yeast strain with the required fermentation and recycling characteristics is critical. The yeast strain will influence the rate and extent of fermentation, the flavour characteristics and the overall quality and stability of the finished beer, and consequently, the economic viability of the brewery. Since high gravity worts can have a deleterious effect on yeast fermentation performance, it is imperative that the strain selected be suitable for this environment, which includes a capacity to withstand high osmotic pressures and elevated ethanol levels. Under controlled in vitro osmotic and ethanol induced stresses, there was a decline in mean cell volume in both lager and ale yeast strains. Whilst significant reductions in viability were observed in the lager strains, the ale strains studied were not affected. Cell surface investigations revealed shrinkage of the yeast cells and crenation of the outside envelope under both stresses, although exposure to ethanol had a more marked effect on the yeast cell surface than sorbitol-induced elevated osmotic pressure.Key words: Cell viability, cell volume, ethanol, high gravity wort, osmotic pressure. -2863(9'8-32In brewing, yeast is recycled and the fact that it is cropped and repitched into subsequent fermentations is one of the differentiating features between brewing and the production of many other alcoholic beverages including Scotch whisky 37 . Consequently, the quality of yeast cropped will not only affect the overall performance of most fermentations but also the quality and stability of the resulting beer. It is important therefore that the factors which influence yeast performance in the brewing process, and particularly in high gravity brewing, are considered, to ensure efficient fermentation and the production of a beer of a consistently high quality and stability. Breweries, the world-over, are continually seeking ways to reduce capital expenditure, labour, utilities, effluent and other operational costs and at the same time ensuring that the quality of their beers remains consistently high. As a result, many are employing the process of high gravity brewing due to its many advantages 39 . Similarly, some breweries have not implemented this process due to its disadvantages 40 . Of significance, are the deleterious effects of this process on yeast fermentation performance 41,43 . Fermentations have been reported to be sluggish due to elevated ethanol levels and high osmotic pressure, resulting in yeast viability and vitality reductions 6 . Osmotic pressure is the force that develops between two solutes of differing concentration separated by a semipermeable membrane 20 . When yeast is exposed to wort it is subjected to an osmotic pressure. Very high osmotic pressures such as those encountered in high gravity worts, may distort yeast metabolism or decrease yeast viability. The extent of the osmotic pressure will depend on the concentration of solutes surrounding the cell 20,23 . It has been shown that increases in wort osmotic pressu...

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Section: (-7'977-32supporting

confidence: 87%

The Effects of Osmotic Pressure and Ethanol on Yeast Viability and Morphology

Pratt

Bryce

Stewart

2003

Journal of the Institute of Brewing

104

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“…These results can be compared with those obtained by Gervais et al (1992) and Marechal and Gervais (1994) on yeasts. These authors have shown the influence of a drastic water potential variation on the survival of 5'.…”

Section: Discussionmentioning

confidence: 87%

“…Cells were maintained at final water potential during 30 min and a viability measurement was performed by using the dilution method, as proposed by Gervais et al (1992). Dilutions were done with a solution (water-glycerol) of the same water potential as the final one.…”

Section: Viability Measurementmentioning

confidence: 99%

Effects of the kinetics of water potential variation on bacteria viability

1997

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I. P O I R I E R , P . -A . MARECHAL A N D P. GERVAIS. 1997. The effect of the kinetics of water potential variation (' 3' ) on the viability of bacteria subjected to hyperosmotic stresses in waterglycerol solution was studied. T h e three bacteria used were Lactobacillus plantarum L-73, Leuconostoc mesentemides LM057 and Escherichia cob TG 1. These strains were submitted to a final water potential of -107.2 MPa, -170.9 M P a and/or -244.7 MPa. I n any case the kinetics of water potential variation was found to have a great effect on the cell viability. T h e application of slow water potential decreases could maintain an important cell viability (about SO-100°/o) with regard to the corresponding viability observed after a sudden step change for the same final water potential (15-57%). For each strain tested, an optimal dehydration kinetics was determined which depended on the final water potential. T h e existence of this optimum could be explained thanks to the opposition of two actions affecting cell viability : a positive action relative to the slowness of the water potential variation and a negative action relative to the residence time of cells in a critical range of water potential.

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“…Some studies have shown that cell death during desiccation is strongly related to membrane integrity loss, leading to cell lysis during rehydration Laroche et al, 2001;Simonin et al 2007;. A gradual dehydration kinetics, which allows a slow water efflux through the plasmatic membrane and homogenous desiccation, followed by a progressive rehydration during the starter preparation, have been related with high cell viability (Gervais et al, 1992;Marechal, 1994¸ Dupont et al, 2010). The amount of cell constituents leaked during rehydration can also be reduced by adding emulsifiers, such as sorbitan monostearate (Chen and Chiger, 1985).…”

Section: Desiccation Of Wine Yeastsmentioning

confidence: 99%