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  • 1
    Electronic Resource
    Electronic Resource
    Induction of flocculation in brewing yeasts by change in pH value (1996)
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology letters 136 (1996), S. 0 
    Details
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract Most brewing strains of Saccharomyces cerevisiae flocculate following growth in beer wort. However, many do not flocculate in laboratory culture media, because their initial pH and buffering capacity do not correspond to the pH range within which these yeasts flocculate. Many, though not all, NewFlo phenotype brewing yeasts flocculate within a narrow pH range only; this is indicative of the existence of more than one NewFlo flocculation phenotype. Such strains may be flocculated by small alterations of pH to within the flocculation range. Induction of flocculation by pH change may be used to separate cells from media at any stage during fermentation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1574-6968.1996.tb08018.x
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  • 2
    Electronic Resource
    Electronic Resource
    Selective separation of microorganisms by lectins: Yeast and concanavalin A as a model system (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 40 (1992), S. 835-843 
    Details
    ISSN: 0006-3592
    Keywords: yeast ; aggregation ; separation ; lectin ; concanavalin A ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Specific aggregation and separation of microorganisms was investigated using yeasts and concanavalin A as a model system. Cells of Saccharomyces cerevisiae were specifically aggregated and so separated from those of Schizosaccharomyces pombe. Optimum aggregation with over 99% of cells aggregated was achieved by adjustment to pH value and applied agitation. Dimeric lectin structure caused a far higher degree of aggregation than did tetrameric. Degree of aggregation was also strongly influenced by the ratio of lectin/cell concentrations, optimum aggregation occurring in the middle range of ratios. A high ratio of lectin to cells inhibited aggregation, occupation of most of the available receptors preventing intercellular bonding by divalent lectins. Detachment and reuse of concanavalin A was demonstrated using switching from moderate to low pH value. Potential uses for species-specific-separation of microorganisms are discussed. © 1992 John Wiley & Sons, Inc.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260400711
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  • 3
    Electronic Resource
    Electronic Resource
    Yeast flocculation: Cationic inhibition (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Yeast 6 (1990), S. 77-86 
    Details
    ISSN: 0749-503X
    Keywords: Flocculation ; yeast ; salt inhibition ; pH value ; Life and Medical Sciences ; Genetics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: Yeast flocculation was inhibited by high concentrations of a number of salts. Calcium and magnesiun salts were potent inhibitors and cesium salts were least effective. Partial inhibitors by different salts additive and were completely reversible by salt removal. Inhibition by salts was time dependent; prolonged incubation increased the degree of inhibition. Salt inhibition was partly caused by the action of salts lowering the buffer pH value, and partly caused by chaotropic inhibition of proteins on the surfaces of flocculent cells. Flocculation receptors on non-flocculent cells were ubaffected by high salt concentration. At sub-inhibitory salt concentrations, there was an enhancement of flocculation in both rate and extent.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/yea.320060109
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  • 4
    Electronic Resource
    Electronic Resource
    Yeast flocculation: Lectin synthesis and activation (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Yeast 9 (1993), S. 371-378 
    Details
    ISSN: 0749-503X
    Keywords: Yeast ; flocculation ; onset ; lectin ; cycloheximide ; heat activation ; Life and Medical Sciences ; Genetics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: Yeast flocculation involves binding of surface lectins to carbohydrate receptors on neighbouring cell walls. Brewing strains of Saccharomyces cerevisiae normally become flocculent in the stationary phase of growth. This paper presents evidence that lectins are synthesized in exponential phase, inserted into the cell wall, and activated later at the time of flocculation onset.Cycloheximide failed to prevent flocculation unless it was added in early growth; with later additions progressively larger degrees of flocculation occurred. Flocculation onset was delayed by cycloheximide but was otherwise cycloheximide insensitive. Preflocculent cells could be artificially activated to full flocculation by heat. Artificial activation of samples from growing yeast cultures confirmed the progressive synthesis of lectins throughout exponential growth. Pronase E treatment of whole cells prior to heating prevented any activation of flocculation.It was concluded that lectins were synthesized continuously from an early stage of growth and rapidly inserted into the cell wall (accessible by pronase E), where they remained inactive for up to 14 h, before being activated at flocculation onset by an as-yet unknown mechanism. It was found that lectin synthesis and activation occurred in all brewing strains tested.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/yea.320090407
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  • 5
    Electronic Resource
    Electronic Resource
    Yeast flocculaiton: A dynamic equilibrium (1988)
    New York, NY [u.a.] : Wiley-Blackwell
    Yeast 4 (1988), S. 199-208 
    Details
    ISSN: 0749-503X
    Keywords: Flocculation ; yeast ; agitation ; equilibrium ; mannose ; pH value ; Life and Medical Sciences ; Genetics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: The steady state in yeast flocculation is a dynamic equilibrium between flocculated and dispersed yeast cells. The free cell concentraiton is directly proportional to the total cell concentration and may be expressed as an equilibrium constant. Increased agitation decreases floc size and equlibrium constant whilst increasing floc-surface area and free cell concentration. Values of equilibrium constant are influenced by agitation in a complex relationship probably involving the floc-surface area and floc momentum.Inhibition of flocculation by mannose and low pH is reversible and becomes greater with increased agitation. Both these inhibitions appear consistent with a weakening of flocculent bond strength by these inhibitors.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/yea.320040305
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  • 6
    Electronic Resource
    Electronic Resource
    Yeast flocculation: Flo1 and NewFlo phenotypes and receptor structure (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Yeast 7 (1991), S. 559-574 
    Details
    ISSN: 0749-503X
    Keywords: Flocculation ; yeast ; lectin ; receptor structure ; Flo1 ; phenotype ; NewFlo phenotype ; Life and Medical Sciences ; Genetics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: Flocculation characteristics of 42 flocculet strains of Saccharomyces cerevisiae were examined. Two entirely distinct ‘lectin-like’ mechanisms of flocculation were distinguished by sugar, salt, and low pH inhibitions, protease sensitivity, and selective expression of flocculation. One group, termed Flo1 phenotype, was inhibited by mannopyranoses and contained all strains bearing known genes affecting flocculation. The other group, termed NewFlo phenotype, contained the majority of brewery ale strains and was inhibited by manno- and glucopyranoses. Detailed sugar-inhibition work revealed the probable receptor identity of both Flo1 and NewFlo flocculation, as being non-reducing termini of α-(1-3)-linked mannan side branches, two or three mannopyranose residues in length.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/yea.320070604
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  • 7
    Electronic Resource
    Electronic Resource
    Yeast flocculation: Calcium specificity (1989)
    New York, NY [u.a.] : Wiley-Blackwell
    Yeast 5 (1989), S. 487-496 
    Details
    ISSN: 0749-503X
    Keywords: Flocculation ; yeast ; calcium ; cations ; efflux ; Life and Medical Sciences ; Genetics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: Expression of flocculation in yeast requires the presence of multi-charged cations. Calcium ions fulfil this role over a broad pH range. At near neutral pH, magnesium and a variety of transition elements can induce flocculation. Calcium-induced flocculation was competitively inhibited by excess sodium ions whereas magnesium-induced flocculation was not competitively inhibited. Potassium and lithium ions caused similar inhibition but to a lesser extent. 45Ca effux from yeast cells was greatly increased by the external presence of buffer and cations. Inhibition of flocculation by chelating agents, EDTA or EGTA, was overcome by excess calcium ions. Flocculation could not be induced, under these conditions, by excess magnesium or transition-element salts.It was concluded that yeast flocculation has a direct specific requirement for calcium ions. Other ions cause flocculation indirectly by effecting calcium ion leakage from cells, which is then able to initiate flocculation. Low calcium concentrations were susceptible to competitive inhibition by sodium ions present in most acidic buffers. In addition, citrate ions inhibited flocculation, probably by sequestration of leaked calcium. Flocculation by salts, other than calcium, was thus restricted to a neutral or high pH range.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/yea.320050608
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  • 8
    Electronic Resource
    Electronic Resource
    Yeast flocculation: Reconciliation of physiological and genetic viewpoints (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Yeast 8 (1992), S. 25-38 
    Details
    ISSN: 0749-503X
    Keywords: Yeasts ; flocculation ; FLO genes ; dsRNA ; Saccharomyces cerevisiae ; brewers' yeast ; Life and Medical Sciences ; Genetics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: Yeast floccultion results from surface expression of specific proteins (lectins). Two flocculation phenotypes were suggested by physiological and biochemical tests, whereas genetic data suggested a larger number of mechanisms of flocculation. After reviewing the biochemistry, physiology and genetics of flocculation, a new hypothesis combining the data available from these different sources, is proposed.Flocculation results when lectins present on flocculent cell bind sugar residues of neighbouring cell walls. These sugar receptors are intrinsic to the mannan comprizing cell walls of Saccharomyces cerevisiae. Two lectin phenotypes were revealed by sugar inhibition studies. The gluco- and mannospecific NewFlo phenotype is not, as yet, found in genetically defined strains. Mannospecific flocculation (Flo 1 phenotype) is found in strains containing the genes FLO1, FLO5 and FLO8. This phenotype is also found following mutation of the TUP1 or CYC8 loci, in previously non-flocculent strains. It is therefore proposed that the structure gene for mannospecific flocculation is common or possibly unbiquitous in non-flocculent strains and in consequence, FLO1, FLO5 and FLO8 are probably regulatory genes, exerting positive control over the structure gene.Flocculation expression requires lectin secretion to the cell surface. Many of the observed ‘suppressions’ of flocculation may be due to mutations of the secretory process, involved in transporting structural proteins to the cell wall.The possible involvement of killer L double-stranded RNA with flocculation is suggested, given the lectin properties of viral coat proteins nad an association between L double-stranded RNA and the Flo 1 phenotype.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/yea.320080103
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  • 9
    Electronic Resource
    Electronic Resource
    Yeast flocculation: Receptor definition by mnn mutants and concanavalin A (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Yeast 8 (1992), S. 635-645 
    Details
    ISSN: 0749-503X
    Keywords: Yeast ; floculation ; receptors ; mnn mutants ; coflocuulation ; concanavalin A ; Life and Medical Sciences ; Genetics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: Yeast flocculation involves the binding of surface lectins on flocculent yeasts, to carbohydrate receptors present as constituents of yeast cell walls. Receptors were investigated by coflocculation of flocculent strains of Saccharomyces cerevisiae, both Flo 1 and NewFlo phenotypes, to known mnn mutants which vary in the wall mannan structure. Strong coflocculation was found with mnn1, mnn4, mnn9 and control strains, while very little coflocculation was found with mnn2 and mnn5 strains. In constrast, aggregation of these muatants by concanavalin A, a lectin with similar sugar inhibition to NewFlo phenotype flocculation, showed strong aggregation of mnn1, mnn4, and mnn5 strains and poor aggregation of mnn2 and mnn9 strains.The mmn mutant data suggested that flocculation receptorss were the outer-chain mannan side-branches, two or three mannose residues in length, confirming an earlier theory based on sugar inhibition data. The similarities and differences between flocculation and concanavalin A aggregation are discussed.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/yea.320080807
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  • 10
    Electronic Resource
    Electronic Resource
    Yeast flocculation: Flocculation onset and receptor availability (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Yeast 9 (1993), S. 85-94 
    Details
    ISSN: 0749-503X
    Keywords: Yeast ; flocculation ; onset ; receptors ; coflocculation ; concanavalin A ; Life and Medical Sciences ; Genetics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: Flocculent strains of brewing yeast grow and ferment as single cells and flocculate in the stationary phase of growth. The switch from single-celled yeast growth to multi-celled aggregation, flocculation onset, is of critical importance to the brewing industry. Yeast flocculation involves adhesion of surface-lectins on flocculent cells to carbohydrate receptors on neighbouring cell-walls. The presence of carbohydrate receptors, outer-chain mannan side-branches, was monitored throughout growth of flocculent and non-flocculent strains of Saccharomyces cerevisiae, with particular attention to the growth phases where flocculation is normally developed. Receptors were probed by coflocculation with flocculent strains and by aggregation with concanavalin A, a lectin shown to use the same receptors as flocculation.While considerable variation was found in coflocculation and concanavalin A aggregation between strains, little or no change in receptor availability was found throughout the growth of all yeast strains. Yeast cells could easily be coflocculated at any growth stage. It was concluded that receptor availability is not involved in the process of flocculation onset.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/yea.320090111
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