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Optimisation of the preservation of microbial cell banks for enhanced fermentation process performance

Hancocks, Nichola Helen (2011)
Ph.D. thesis, University of Birmingham.

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This work discusses optimisation of the cryopreservation of Bacillus licheniformis cell banks, used as inoculum for α-amylase producing 5 L batch fermentations. The effect of the presence of various cryopreservants including glycerol, Tween 80 and dimethyl sulphoxide on final fermentation performance measured by biomass and α-amylase concentration was investigated using optical density, dry cell weight, colony forming units, and multi-parameter flow cytometry. The application of multi-parameter flow cytometry using the fluorophores DiBac\(_4\)(3) and PI allowed real time viability measurements of individual microbial cells to be monitored before and after cryopreservation and during the fermentation process; viability here being defined as a cell having an intact and fully polarised cytoplasmic membrane. It was found that the concentration and type of cryopreservant used had a significant effect on microbial cell physiology and population heterogeneity during resuscitation recovery immediately after thawing. Cell banks prepared with Tween 80 were fastest to recover after freezing in comparison to cell banks prepared with dimethyl sulphoxide which showed the slowest growth rates. Interestingly cells preserved in glycerol recovered at a similar rate to cells frozen without cryopreservant. Despite different responses to the freezing process when each cell bank was used as inoculum for 5 L batch fermentations very little difference was noticed in overall process performance with respect to α-amylase production, growth rate and final biomass concentration.

Type of Work:Ph.D. thesis.
Supervisor(s):Thomas, C. R. (Colin R.) and Hewitt, Christopher
School/Faculty:Colleges (2008 onwards) > College of Engineering & Physical Sciences
Department:School of Chemical Engineering
Subjects:TP Chemical technology
Institution:University of Birmingham
ID Code:547
This unpublished thesis/dissertation is copyright of the author and/or third parties. The intellectual property rights of the author or third parties in respect of this work are as defined by The Copyright Designs and Patents Act 1988 or as modified by any successor legislation. Any use made of information contained in this thesis/dissertation must be in accordance with that legislation and must be properly acknowledged. Further distribution or reproduction in any format is prohibited without the permission of the copyright holder.
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