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Title: Development of a dialysis membrane bioreactor for beverage dealcoholisation
Author: Palmer, S. M.
Awarding Body: University of Wales Swansea
Current Institution: Swansea University
Date of Award: 2004
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The objective of this work was to remove ethanol from an alcoholic beverage using the aerobic biochemistry of the yeast Saccharomyces cerevisiae and a Dialysis Membrane as an anaerobic/aerobic barrier, between this yeast and the potable beverage. Ethanol, as the carbon substrate is then delivered to the yeast cells by molecular diffusion. To assess the uptake of ethanol as a sole carbon substrate, several stirred tank fermenter (STF) experiments were carried out, with various starting conditions, in particular initial yeast biomass concentration and cell population age. This work showed the benefits of a high initial biomass concentration to minimise batch process time by increasing the rate of bioreaction, mass transfer limitations at the membrane interfacial area having essentially been engineered out in the design of the system, as reported. The benefit of high yeast biomass concentrations are proposed to be dependent on a specific ethanol concentration factor, (per yeast cell), termed the Specific Exposure Factor, (SEF). Through mathematical models developed in this work, mass transfer and bioreaction rates have been assessed, the controlling step being quantified by the dimensionless Kaliber Number (Ka). Through the use of developed dimensionless plots, and comparison of the Monod kinetic parameters given by the models presented, a study of yeast biomass growth and ethanol substrate utilisation is made. Whilst the suppression of yeast growth kinetic performance on ethanol substrate was somewhat variable in the Membrane Bioreactor, the variance did not affect the ethanol substrate uptake kinetic performance of the aerobic yeast cells, which remained remarkably consistent. Ethanol utilisation, (as the limiting carbon substrate), is shown to be by inhibited passive transport at the yeast cell membrane. A comparison of ethanol substrate metabolism to that of glucose has been made.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available