Yeast flocculation: what brewers should know

Verstrepen, Kevin J.; Derdelinckx, Guy; Verachtert, Hubert; Delvaux, Freddy R.

doi:10.1007/s00253-002-1200-8

Cited by 289 publications

(251 citation statements)

References 62 publications

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“…The present review targets practical aspects of yeast flocculation that are relevant to brewer's yeast strains under industrial brewery conditions. Earlier reviews include Verstrepen et al, 2003 103 , Verstrepen and Klis, 2006 106 and Soares, 2010 73 and a recent symposium contains relevant articles 76 .…”

Section: Introductionmentioning

confidence: 99%

125th Anniversary Review: Yeast Flocculation and Sedimentation in Brewing

Vidgren

Londesborough

2011

Journal of the Institute of Brewing

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Flocculation is prerequisite for bulk sedimentation of yeast during brewery fermentation. Although single yeast cells gradually sediment in green beer, this sedimentation rate is too slow without formation of large yeast flocs. The present review concerns the major determinants of yeast flocculation and sedimentation in brewery fermentations. Flocculation characteristics of yeast are strongly strain-dependent and largely defined by which FLO genes are functional in each strain. In addition to the genetic background, several environmental factors affect flocculation. These can be, somewhat arbitrarily, classified as physiological factors, such as the calcium availability, pH, temperature and ethanol and oxygen concentrations in the medium or physical factors, such as cell surface hydrophobicity, cell surface charge and the presence of appropriate hydrodynamic conditions for the formation of large flocs. Once yeast flocs are formed, their size, shape and density and the properties of the surrounding medium affect the rate at which the flocs sediment. Higher gravity worts usually result in green beers with higher viscosity and density, which both retard sedimentation. Moreover, environmental factors during yeast handling before fermentation, e.g., propagation, storage and cropping, influence the flocculation potential of yeast in subsequent fermentation. Premature yeast flocculation (PYF) and the role of PYF factors are discussed. In conclusion, some potential options available to adjust yeast flocculation are described.

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Section: Introductionmentioning

confidence: 99%

125th Anniversary Review: Yeast Flocculation and Sedimentation in Brewing

Vidgren

Londesborough

2011

Journal of the Institute of Brewing

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“…The application of flocculating strains to industrial fermentation processes removes the need for extensive and costly cell separation equipment, and these yeasts are thus suitable for both fedbatch and continuous fermentation. [1][2][3][4] In addition, flocculating yeast cells are useful in immobilized cell systems with no inert support materials. 5) However, although flocculation mechanisms and the introduction of this property to non-flocculent yeast strains have been extensively studied in S. cerevisiae, few studies of this nature have been undertaken in other yeast species.…”

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confidence: 99%

Construction of FlocculentKluyveromyces marxianusStrains Suitable for High-Temperature Ethanol Fermentation

Nonklang

Ano²,

Abdel-Banat

et al. 2009

Bioscience, Biotechnology, and Biochemistry

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Flocculating yeasts are highly useful in fermentation processes because these cells can be separated easily from the fermentation mash. However, native yeasts are usually non-flocculating, including Kluyveromyces marxianus, which exhibits a potent high-temperature ethanol fermentation ability. We describe here the construction of flocculent K. marxianus strains via the introduction of the FLO1, FLO5, FLO9, and FLO10 genes from Saccharomyces cerevisiae. The S. cerevisiae FLO genes were overexpressed by upstream insertion of the constitutive TDH3 promoter, resulting in flocculent S. cerevisiae strains. These TDH3p-FLO sequences were then amplified by PCR and introduced directly into a K. marxianus strain. These K. marxianus strains showed a flocculation phenotype, indicating that the introduced S. cerevisiae TDH3 promoter and all FLO genes were functional in this strain. Moreover, a flocculating K. marxianus strain showed the same ethanol production profile as that of its wild-type parent. The K. marxianus flocculating strains we generated should be useful in the future development of cost-effective fed-batch and continuous fermentation systems at high temperatures.Key words: Kluyveromyces marxianus; yeast; flocculation; ethanol fermentationFlocculation is an attractive property in industrial yeasts because the cells can be easily separated from a fermentation mash. The application of flocculating strains to industrial fermentation processes removes the need for extensive and costly cell separation equipment, and these yeasts are thus suitable for both fedbatch and continuous fermentation. [1][2][3][4] In addition, flocculating yeast cells are useful in immobilized cell systems with no inert support materials. 5) However, although flocculation mechanisms and the introduction of this property to non-flocculent yeast strains have been extensively studied in S. cerevisiae, few studies of this nature have been undertaken in other yeast species. 6,7) The mechanism of yeast flocculation involves the interaction of lectin-like proteins, called flocculins, with receptors on a neighboring cell wall, resulting in the formation of aggregates. [8][9][10][11] Environmental factors such as pH, calcium, and organic stress also affect flocculation. 9,[12][13][14] The five FLO genes, FLO1, FLO5, FLO9, FLO10, and FLO11, have been described in S. cerevisiae thus far. [15][16][17][18][19] The FLO1, 5, 9, and 10 genes confer cell-cell adhesion (flocculation) ability, whereas FLO11 is responsible for substrate adhesion. 20) FLO1, FLO5, and FLO9 are highly similar to each other, but FLO10 has lower similarity. The mechanisms of flocculation in other yeasts appear to be lectin-based but of differing specificities. For instance, galactose and its derivatives have been found to inhibit flocculation of K. bulgaricus and K. lactis, suggesting that this interaction involves a galactose-specific lectin. 21,22) The advantages of using flocculating yeast cells in fermentation processes have led to many studies on the construction of flocculent s...

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“…Cell surface hydrophobicity has been identified as the second major factor responsible for flocculation onset 1,6,[21][22][23]28 . This observation was further supported by the accumulation of hydrophobic carboxylic acids i.e.…”

Section: Introductionmentioning

confidence: 99%

“…Flocculation is the phenomenon whereby yeast cells spontaneously adhere in clumps and sediment rapidly from the medium in which they are suspended 28 . This phenomenon is of great interest in brewing and many other fermentation industries.…”

Section: Introductionmentioning

confidence: 99%

Oxylipin Associated Co-Flocculation in Yeasts

Strauss

Wyk

Lodolo³

et al. 2006

Journal of the Institute of Brewing

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According to the lectin-theory, the yeast Schizosaccharomyces pombe lacks the specific receptors (␣-mannans) necessary to facilitate co-flocculation with Saccharomyces cerevisiae species.In this study we demonstrate oxylipin associated co-flocculation between Sacch. cerevisiae and S. pombe strains using differential cell staining, immunofluoresence and ultrastructural studies. Using a 3-hydroxy (OH) oxylipin specific antibody coupled to a fluorescing compound, 3-OH oxylipins were found to be present on the cell surfaces of Sacch. cerevisiae and S. pombe. The presence of 3-OH oxylipins was confirmed using gas chromatography-mass spectrometry. Strikingly, when acetylsalicylic acid (aspirin), a 3-OH oxylipins inhibitor, was added to Sacch. cerevisiae which was then mixed with S. pombe strains grown in complex media, co-flocculation was significantly inhibited. We conclude that aspirin-sensitive 3-OH 8:0 is probably involved in co-flocculation.

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Yeast flocculation: what brewers should know

Cited by 289 publications

References 62 publications

125th Anniversary Review: Yeast Flocculation and Sedimentation in Brewing

125th Anniversary Review: Yeast Flocculation and Sedimentation in Brewing

Construction of FlocculentKluyveromyces marxianusStrains Suitable for High-Temperature Ethanol Fermentation

Oxylipin Associated Co-Flocculation in Yeasts

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