Characteristics of High Cell Density Fermentations with Different Lager Yeast Strains

Verbelen, Pieter J.; Mulders, Sebastiaan Van; Saison, Daan; Laere, Stijn Van; Delvaux, Freddy R.

doi:10.1002/j.2050-0416.2008.tb00317.x

Cited by 34 publications

(33 citation statements)

References 23 publications

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“…These results share similarity with a previous report [70]. On the contrary, Verbelen et al [80] reported that the inXuence of pitching rate on aroma compound production was rather limited, with the exception of total diacetyl levels, which strongly increased with the pitching rate.…”

Section: Yeast Pitching Ratesupporting

confidence: 86%

Very high gravity (VHG) ethanolic brewing and fermentation: a research update

Puligundla

Šmogrovičová

Obulam

et al. 2011

J Ind Microbiol Biotechnol

175

109

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There have been numerous developments in ethanol fermentation technology since the beginning of the new millennium as ethanol has become an immediate viable alternative to fast-depleting crude reserves as well as increasing concerns over environmental pollution. Nowadays, although most research efforts are focused on the conversion of cheap cellulosic substrates to ethanol, methods that are cost-competitive with gasoline production are still lacking. At the same time, the ethanol industry has engaged in implementing potential energy-saving, productivity and efficiency-maximizing technologies in existing production methods to become more viable. Very high gravity (VHG) fermentation is an emerging, versatile one among such technologies offering great savings in process water and energy requirements through fermentation of higher concentrations of sugar substrate and, therefore, increased final ethanol concentration in the medium. The technology also allows increased fermentation efficiency, without major alterations to existing facilities, by efficient utilization of fermentor space and elimination of known losses. This comprehensive research update on VHG technology is presented in two main sections, namely VHG brewing, wherein the effects of nutrients supplementation, yeast pitching rate, flavour compound synthesis and foam stability under increased wort gravities are discussed; and VHG bioethanol fermentation studies. In the latter section, aspects related to the role of osmoprotectants and nutrients in yeast stress reduction, substrates utilized/tested so far, including saccharide (glucose, sucrose, molasses, etc.) and starchy materials (wheat, corn, barley, oats, etc.), and mash viscosity issues in VHG bioethanol production are detailed. Thereafter, topics common to both areas such as process optimization studies, mutants and gene level studies, immobilized yeast applications, temperature effect, reserve carbohydrates profile in yeast, and economic aspects are discussed and future prospects are summarized.

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Section: Yeast Pitching Ratesupporting

confidence: 86%

Very high gravity (VHG) ethanolic brewing and fermentation: a research update

Puligundla

Šmogrovičová

Obulam

et al. 2011

J Ind Microbiol Biotechnol

175

109

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“…Similar concentrations were detected by Verbelen et al (2009a) in beer. Other authors showed that ester levels were negatively influenced by higher pitching rates (Verbelen et al, 2008). A similar result was observed in this study for isoamyl acetate and 2-phenylethyl acetate, compounds with fruity and flowery flavours, respectively.…”

Section: Effect Of Pitching Rate On Mead Aroma Profilesupporting

confidence: 77%

“…No differences in 3-methyl-1-butanol were observed in meads fermented at different pitching rates by the strain ICV D47, whereas a higher concentration of this alcohol was detected only at the lowest pitching rate (1.5 Â 10 5 CFUs/mL) with the strain QA23. Different results were obtained by Mateo et al (2001), Erten et al (2006), Verbelen et al (2008) and Verbelen et al (2009a), who indicated a direct dependence of the concentration of that compound on inoculum size. Esters represented the most diverse group with ten compounds quantified.…”

Section: Effect Of Pitching Rate On Mead Aroma Profilementioning

confidence: 92%

High-cell-density fermentation of Saccharomyces cerevisiae for the optimisation of mead production

et al. 2013

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a b s t r a c tMead is a traditional drink that contains 8%e18% (v/v) of ethanol, resulting from the alcoholic fermentation of diluted honey by yeasts. Mead fermentation is a time-consuming process and the quality of the final product is highly variable. Therefore, the present investigation had two main objectives: first, to determine the adequate inoculum size of two commercial wine-making strains of Saccharomyces cerevisiae for the optimisation of mead fermentation; and second, to determine if an increase in yeast pitching rates in batch fermentations altered the resulting aroma profiles. Minor differences were detected in the growth kinetics between the two strains at the lowest pitching rate. With increasing pitching rates net growth of the strain ICV D47 progressively decreased, whereas for the QA23 the increasing inoculum size had no influence on its net growth. The time required to reach the same stage of fermentation ranged from 24 to 96 h depending on the inoculum size. The final aroma composition was dependent on the yeast strain and inoculum size. Fourteen of the twenty-seven volatile compounds quantified could contribute to mead aroma and flavour because their concentrations rose above their respective thresholds. The formation of these compounds was particularly pronounced at low pitching rates, except in mead fermented by strain ICV D47, at 10 6 CFUs/mL. The esters isoamyl acetate, ethyl octanoate and ethyl hexanoate were the major powerful odourants found in the meads. The results obtained in this study demonstrate that yeast strain and inoculum size can favourably impact mead's flavour and aroma profiles.

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“…However, the levels of aroma compounds, especially esters, in beer vary with fermentation temperature (20,30). Increasing the yeast inoculum also alters the aroma profile and increases fermentation rate but only up to a limit (22,28,29).…”

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confidence: 99%

Selection from Industrial Lager Yeast Strains of Variants with Improved Fermentation Performance in Very-High-Gravity Worts

Huuskonen

Markkula

Vidgren

et al. 2010

Appl Environ Microbiol

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o P), producing beers containing higher concentrations of ethanol, which are then diluted to drinking strength. These high-gravity worts often contain adjunct carbohydrates in addition to those from the barley malt. Because the adjunct carbohydrates contain a higher proportion of fermentable sugars, relatively more ethanol is produced from each degree Plato of extract. Fermenting at high gravity provides increased production capacity from the same size brewhouse and fermentation facilities and thus decreases capital investment costs. Other advantages are decreases in energy consumption and in labor, cleaning, and effluent costs (26). These advantages would be greater if very-high-gravity (VHG) worts could be used. Above about 18 o P, however, fermentation rates decrease disproportionately (i.e., it takes longer to ferment the same mass of sugar in the more concentrated wort), fermentations do not go to completion (i.e., unacceptably large concentrations of sugars, especially maltotriose, remain in the final beers, causing low ethanol yields and undesirable flavor), and the physiological condition of the yeast at the end of fermentation is poor (4,7,17,27,35). It is standard practice to crop (harvest) yeast at the end of brewery fermentations and to use this cropped yeast to pitch (inoculate) subsequent fermentations. Thus, it is important that the viability of the cropped yeast is high (Ͼ90%). Other problems in high-gravity and VHG wort fermentations include poor foam stability, possibly caused by the release of proteolytic enzymes from highly stressed yeast cells (6), haze or turbidity caused by release of glycogen from lysed yeast (18), and alterations in aroma profile. In particular, the concentration of some aroma esters in beers depends on the original gravity of the wort (20) as well as on the sugar composition (16, 33) and the ratio of total sugars to free amino nitrogen (FAN) (1, 14, 22).

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Characteristics of High Cell Density Fermentations with Different Lager Yeast Strains

Cited by 34 publications

References 23 publications

Very high gravity (VHG) ethanolic brewing and fermentation: a research update

Very high gravity (VHG) ethanolic brewing and fermentation: a research update

High-cell-density fermentation of Saccharomyces cerevisiae for the optimisation of mead production

Selection from Industrial Lager Yeast Strains of Variants with Improved Fermentation Performance in Very-High-Gravity Worts

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