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Title: Continuous lactic acid fermentation in a hollow fibre reactor
Author: Hamilton, K. M.
Awarding Body: University College of Swansea
Current Institution: Swansea University
Date of Award: 1983
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Hollow fibre membranes may be used for aerobic and anaerobic fermentations. For aerobic systems, tube side aeration gave better oxygen flux than aeration through the shell side. A zero order steady-state diffusion control model was constructed. Concentration and flux profiles for glucose and oxygen in the fibre wall were calculated, together with Thiele moduli and effectiveness factors. Analysis of oxygen as the limiting step led to the development of two design parameters for scale up. Proposed optimum values of these are given. The model does not require the assumption of zero oxygen concentration or flux at the wall, but allows the oxygen to be depleted at some point within the wall. High yields were obtained using mixed and pure lactic and hollow fibre fermentations. In the mixed culture, shown to exhibit neutralism, increases in lactate yields were attributable to ecological changes. The reaction rate showed feed flow dependence below a critical value. In the pure culture continuous runs, as the growth rate increased almost exponentially, the lactate production rate remained almost constant with an increasing biomass/substrate yield. Whilst the Leudeking-Piret equation was successfully fitted to the batch controls, it could not interpret the data of the continuous hollow fibre experiments. The cell metabolism model successfully interpreted the results of the lactate hollow fibre fermentations. The model postulates two pathways, pentose phosphate and glycolysis, and their regulating mechanisms are key to bacterial metabolism. Bioenergetic evidence supported the model and biochemical reactions were proposed as a controlling mechanism. The model may have broad application to conventional lactate fermentations, being capable of predicting normal trends in lag and log phases. Hollow fibre fermentations appear to prolong aseptic cell growth. In contrast to a CSTR, this reactor may allow continuous fermentation of organisms with slow growth rates.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available