The strength of yeast flocs produced by the cationic flocculant chitosan: Effect of suspension medium and of pretreatment with anionic polyelectrolytes

Weir, Steve; Ramsden, D. K.; Hughes, J. C.; Thomas, F.

doi:10.1007/bf00152853

Cited by 5 publications

(3 citation statements)

References 9 publications

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“…Secondly, the formation of a chitosan -cellulosic macromolecular complex could facilitate the formation of macroscopic floes through the bridging of individual microflocs. The floes thus formed are stronger than those produced naturally by the bridging of cellulosic materials alone ( Beker et al, 1988 ) and could be made even stronger by the further addition of anionic polyelectrolytes ( Weir et al, 1994 ).…”

Section: Discussionmentioning

confidence: 99%

The role of cellulosics in chitosan flocculation of Zymomonas mobilis

Hughes¹,

Ramsden

Boulby

1994

Biotechnol Tech

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The floes produced by an autoflocculent strain of Zyrrzomonus mobilis are easily disrupted by gentle agitation. Treatment of a disrupted cell suspension with the flocculant chitosan yields less easily disrupted floes. The effectiveness of chitosan is attributed to the hydrogen bonding of the flocculant with the cell-bound and free cellulosic materials which facilitate polymer bridging and an electrostatic interaction between the cell wall and the flocculant.

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Section: Discussionmentioning

confidence: 99%

The role of cellulosics in chitosan flocculation of Zymomonas mobilis

Hughes¹,

Ramsden

Boulby

1994

Biotechnol Tech

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“…This was an example of many of the attempts that have been made in order to reduce diffusional limitations in flocs through the use of polymeric additives [142,145,146]. Those additives should enlarge the space between adjacent cells, extending the bridges that link the cells in a floc [119].…”

Section: Mass Transfer In Flocculating Cell Culturesmentioning

confidence: 99%

Applications of yeast flocculation in biotechnological processes

Domingues

Vicente

Lima

et al. 2000

Biotechnol. Bioprocess Eng.

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A review on the main aspects associated with yeast flocculation and its application in biotechnological processes is presented. This subject is addressed following three main aspects -the basics of yeast flocculation, the development of "new" flocculating yeast strains and bioreactor development. In what concerns the basics of yeast flocculation, the state of the art on the most relevant aspects of mechanism, physiology and genetics of yeast flocculation is reported. The construction of flocculating yeast strains includes not only the recombinant constitutive flocculent brewer's yeast, but also recombinant flocculent yeast for lactose metabolisation and ethanol production. Furthermore, recent work on the heterologous β-galactosidase production using a recombinant flocculent Saccharomyces cerevisiae is considered. As bioreactors using flocculating yeast cells have particular properties, mainly associated with a high solid phase hold-up, a section dedicated to its operation is presented. Aspects such as bioreactor productivity and culture stability as well as bioreactor hydrodynamics and mass transfer properties of flocculating cell cultures are considered. Finally, the paper concludes describing some of the applications of high cell density flocculation bioreactors and discussing potential new uses of these systems.

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“…Attempts have been made in order to reduce diffusional limitations in¯ocs through the use of polymeric additives [6,15,16]. Yeast¯ocs form, according to Miki et al [17] as`a speci®c lectin-like component of the cell wall recognises and adheres to a-mannan carbohydrate on an adjoining cell, Ca 2+ ions acting as a cofactor activating the binding capacity''.…”

Section: Introductionmentioning

confidence: 99%

Modelling diffusion-reaction phenomena in yeast flocs of Saccharomyces cerevisiae

Vicente

Dluhý

Ferreira

et al. 1998

Bioprocess Engineering

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Limitations in the diffusion of substrates into the¯ocs will condition cell metabolic behaviour, having obvious consequences on growth and product formation. Polymeric additives have been used aiming the reduction of those limitations. The knowledge of the concentration pro®les and metabolic¯uxes of glucose and oxygen inside the¯ocs would bring valuable information about the conditions under which a fermentation should run. Direct measurement of such pro®les is rather dif®cult but their simulation has been performed and is presented in this work.Calculations were made for different possible sizes of the yeast¯ocs, considering also the presence or absence of a polymeric additive. Only a small percentage of the cells in the¯ocs metabolise glucose oxidatively due to severe oxygen limitations. The presence of the polymeric additive increases the ratio of cells operating under respiratory metabolism over those under fermentative metabolism: from 0.4% to 5.7% without additive to 1.2% to 8.5% with additive, depending on the bulk glucose concentration. Also, based on this data, it is possible to justify the yeast oc natural shape.List of symbols a speci®c mass transfer area, 1/m

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The strength of yeast flocs produced by the cationic flocculant chitosan: Effect of suspension medium and of pretreatment with anionic polyelectrolytes

Abstract: The strength of floes formed by the chitosan induced flocculation of yeast depends on the nature of the suspending medium. The addition of anionic polymers to the medium prior to flocculation by the cationic polyelectrolyte chitosan can increase the resilience of the floes.

Cited by 5 publications

References 9 publications

The role of cellulosics in chitosan flocculation of Zymomonas mobilis

The role of cellulosics in chitosan flocculation of Zymomonas mobilis

Applications of yeast flocculation in biotechnological processes

Modelling diffusion-reaction phenomena in yeast flocs of Saccharomyces cerevisiae

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