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Title: Interaction between gel strength and yeast cells immobilized in calcium alginate gel
Author: Kokkinakis, E. N.
Awarding Body: University College of Swansea
Current Institution: Swansea University
Date of Award: 1994
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The objective of the project is to improve the durability of calcium alginate gel, as an immobilizing matrix for yeast in aerobic culture, by increasing the alginate content of the gel in the range 4.5, 6.0, and 8.0 wt%, so that the immobilized yeast bioparticle can be used for at least 500 hours continuous culture, and to investigate the interaction between the gel matrix and the immobilized cells. The yeast, S.cerevisiae NCYC 1026, has been aseptically immobilized in thin calcium alginate gel discs (2.0 mm by 7.0 mm) of the required alginate content, and aerobically cultured at + 25°C and pH 4.5 in a chemically defined liquid culture medium. The immobilized yeast gel discs have been continuously cultured in an air lift bioreactor for at least 500 hours. The kinetic state of the immobilized cells and the immobilized biomass hold-up were measured independently, such that these data were available for the analysis of the continuous bioreactor, using mathematical models of the bioreaction system. The calcium alginate gel was found to reduce yeast growth and yield slightly, but to have a significant effect on glucose uptake by inducing active transport in the yeast. Otherwise the gel had no adverse action on the yeast, indeed the gel matrix tended to maintain yeast viability, when the immobilized cell gel discs were stored for up to 3 months with no glucose supply. During continuous culture the key operational parameters were found to be effective diffusivity of glucose in the gel matrix solid phase and immobilized cell biomass hold-up, possibly linked to the inconstant cell mass leakage rate from the gel. The 6.0 wt% alginate content gel was found to be the optimum gel for immobilized cell function and durability of the gel. Nevertheless the effective diffusivity even in this gel was only 1.0% of that in water, much lower than previously reported.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available