Leavening ability of baker's yeast exposed to hyperosmotic media

Hirasawa, Reiko; Yokoigawa, Kumio

doi:10.1111/j.1574-6968.2001.tb09462.x

Cited by 29 publications

(10 citation statements)

References 8 publications

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“…SSF of washed pretreated spruce slurry resulted in overall ethanol yields between 68.1 and 77.2%; the lowest ethanol yield being obtained in SSF of the substrate with highest initial concentration of fermentable sugars (see Figure 4). Hyperosmotic stress due to high sugar concentrations results in the accumulation of intracellular glycerol in yeast cells [19,28], which could explain the slight decrease in ethanol yield at the highest glucose concentrations. The differences in the ethanol yields from SSF of washed steam-pretreated spruce slurry with different initial concentrations of fermentable sugars are not sufficient to explain the difference in ethanol yields observed in batch SSF of whole steam-pretreated spruce slurry with and without prehydrolysis (Figure 3).…”

Section: Resultsmentioning

confidence: 99%

“…However, high sugar concentrations can lead to high osmotic pressure in the fermentation medium, which is known to stress the yeast. The incubation of yeast in a medium containing high concentrations of different fermentable sugars has been shown to increase the fermentation ability of the yeast [19]. Thus, high initial concentrations of fermentable sugar as a result of prehydrolysis prior to SSF may influence the fermentation step in the process in various ways.…”

Section: Introductionmentioning

confidence: 99%

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Influence of fiber degradation and concentration of fermentable sugars on simultaneous saccharification and fermentation of high-solids spruce slurry to ethanol

Hoyer

Galbe

Zacchi

2013

Biotechnol Biofuels

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BackgroundSaccharification and fermentation of pretreated lignocellulosic materials, such as spruce, should be performed at high solids contents in order to reduce the cost of the produced bioethanol. However, this has been shown to result in reduced ethanol yields or a complete lack of ethanol production. Previous studies have shown inconsistent results when prehydrolysis is performed at a higher temperature prior to the simultaneous saccharification and fermentation (SSF) of steam-pretreated lignocellulosic materials. In some cases, a significant increase in overall ethanol yield was reported, while in others, a slight decrease in ethanol yield was observed. In order to investigate the influence of prehydrolysis on high-solids SSF of steam-pretreated spruce slurry, in the present study, the presence of fibers and inhibitors, degree of fiber degradation and initial fermentable sugar concentration has been studied.ResultsSSF of whole steam-pretreated spruce slurry at a solids content of 13.7% water-insoluble solids (WIS) resulted in a very low overall ethanol yield, mostly due to poor fermentation. The yeast was, however, able to ferment the washed slurry and the liquid fraction of the pretreated slurry. Performing prehydrolysis at 48°C for 22 hours prior to SSF of the whole pretreated slurry increased the overall ethanol yield from 3.9 to 62.1%. The initial concentration of fermentable sugars in SSF could not explain the increase in ethanol yield in SSF with prehydrolysis. Although the viscosity of the material did not appear to decrease significantly during prehydrolysis, the degradation of the fibers prior to the addition of the yeast had a positive effect on ethanol yield when using whole steam-pretreated spruce slurry.ConclusionsThe results of the present study suggest that the increase in ethanol yield from SSF when performing prehydrolysis is a result of fiber degradation rather than a decrease in viscosity. The increased concentration of fermentable sugars at the beginning of the fermentation phase in SSF following prehydrolysis did not affect the overall ethanol yield in the present study.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Influence of fiber degradation and concentration of fermentable sugars on simultaneous saccharification and fermentation of high-solids spruce slurry to ethanol

Hoyer

Galbe

Zacchi

2013

Biotechnol Biofuels

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“…Saccharomyces cerevisiae cells incubated in 0.2 m glycerol are reported to have high leavening ability in dough containing a high concentration of sucrose (sweet dough). A hyperosmotic medium containing 0.5% yeast extract, 0.5% peptone, and 20% sucrose was developed to increase the fermentation ability of S. cerevisiae (Hirasawa & Yokoigawa, 2001). These authors found a high correlation between intracellular glycerol accumulation and the fermentation ability of the tested yeast.…”

Section: Resultsmentioning

confidence: 99%

A novel steamed bread making process using salt‐stressed baker’s yeast

Yeh

Charles

et al. 2009

Int J of Food Sci Tech

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The process of applying salt-stressed baker's yeast during southern style Chinese steamed bread dough preparation was examined. Baker's yeast was stressed in 7% salt solution then mixed into dough, which was then evaluated for dough fermentation producing gas, dough expansion, texture profile analysis (TPA), colour, specific volume, spread ratio and sensory analysis. The results of this study pointed out salt-stressed baker's yeast produced significant amount of gas and dough expansion, particularly after 40 min of salt stressing. The texture of steamed bread was softer (463.08 g) than control (541.35 g) (P < 0.05), greater in specific volume (3.15 cm 3 g )1 ) than control (2.89 cm 3 g )1 ) (P < 0.05), had a lower spread ratio (1.45) than control (1.74) (P < 0.05) and a significantly improved sensory properties for taste (90.6) than control (81.6) (P < 0.05) were obtained.

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“…The fermentation ability of the yeast cells in LSMLD medium was determined using the method described by Hirasawa and Yokoigawa (2001). An optimal amount of cell mass (0.36 ± 0.005 g dry weight) of yeast was inoculated into 50 ml LSMLD medium in a 150-ml conical flask at 30 °C without shaking.…”

Section: Methodsmentioning

confidence: 99%

Characterisation of maltose metabolism in lean dough by lagging and non-lagging baker’s yeast strains

2008

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Baker's yeast, Saccharomyces cerevisiae, is a key microorganism used in the baking industry. While the preferred substrate for baker's yeast is generally glucose, the predominant carbohydrate in lean dough is maltose. Therefore, in order to improve the leavening properties of lean dough, it is essential to improve maltose metabolism by the yeast. The objective of this study was to gain better insight into the regulation of the yeast maltose-transporter, maltose permease, and the maltose-cleaving enzyme, maltase, by glucose in lagging and non-lagging strains of baker's yeast. Gas evolution in a low sugar model liquid dough (LSMLD) medium was used to select five out of ten industrial baker's yeast strains for further investigation on the basis of varying metabolic characteristics. In all four of the lagging strains tested, both maltose permease and maltase were inhibited by glucose to some extent. In the relative non-lagging strain, which demonstrated the highest performance in LSMLD, it was shown that maltase was not inhibited by glucose. Based on our findings, it indicated that in lean dough leavening, it is the maltase that plays the essential role in maltose metabolism, rather than the maltose permease. Therefore, we propose that the lack of glucose repression on maltase activity is the most critical criterion in the development of non-lagging strains of baker's yeast.

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Leavening ability of baker's yeast exposed to hyperosmotic media

Cited by 29 publications

References 8 publications

Influence of fiber degradation and concentration of fermentable sugars on simultaneous saccharification and fermentation of high-solids spruce slurry to ethanol

Influence of fiber degradation and concentration of fermentable sugars on simultaneous saccharification and fermentation of high-solids spruce slurry to ethanol

A novel steamed bread making process using salt‐stressed baker’s yeast

Characterisation of maltose metabolism in lean dough by lagging and non-lagging baker’s yeast strains

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