The effect of the key physiological parameters on the production of solvents in the acetone-butanol fermentation using the anaerobic bacterium Clostridium acetobutylicum was examined in this work. / The theoretical solvent yield was calculated based on expressing stoichiometric relationships between the substrate and the products of the process. The maximum theoretical yield under the acceptable process conditions was established ranging from 38.6% to 39.9%. / A linear correlation was established between the production of solvents and gases which varied with the mixing rate of the fermentation system. / Elevated hydrogen partial pressure affected the metabolism of C. acetobutylicum resulting in increased butanol and ethanol yields (based on glucose) by an average of 18% and 13%, respectively. / A mathematical model for the batch acetone-butanol fermentation was formulated using original experimental data for the microbial growth, sugar consumption and metabolite biosynthesis. This model was used for computer process simulations. Parametric sensitivity analysis indicated the importance of the key process parameters. / A method of systems analysis was applied in analysing pronounced physiological differences in the performance of one of the C. acetobutylicum culture strains. The cellular transport mechanism for substrate (glucose), solvents and acids through the cell membrane was established to depend on its permeability and the number of sugar transport "sites". Experimental results obtained from the study of the uptake of 3-0-methyl glucose (0.7mM) by the "normal culture" and the "retarded culture" confirmed the theoretical predictions of a slower transpost in the "retarded culture". The theoretical predictions were further confirmed by additional experimental results. / A mathematical "Physiological State Model" was developed which includes the culture physiological parameters as well as the internal and the external culture conditions. Using this mathematical model the standard and the substandard acetone-butanol fermentations could be simulated. / These results demonstrate the application of the method of systems analysis in elucidation of the role played by the key culture physiological parameters in the fermentation process.

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The fermentation of African locust beans was studied. These beans in the raw state are inedible but may be rendered palatable by fermentation. Both their texture and taste are thereby considerably improved. / The beans were first processed by boiling and dehulling. They were then fermented at 37 (+OR-) 2(DEGREES)C in stationary fermentor units. Physico-chemical, microbiological, biochemical and enzymological investigations were carried out on the substrate undergoing spontaneous fermentation and on radappertized (11 kGy) controls. Reductions in carbohydrate (52%), protein (12%) and energy (9%) contents, as obtained from the mass and energy balances, occurred during fermentation. The physico-chemical changes were due to the action of extracellular carbohydrases and proteases produced by a Bacillus spp. Pure culture inoculation with the Bacillus spp. gave the fermented product within 24 h in contrast to the normal 72 h fermentation period. / Both pH and titratable acidity increased during fermentation. Ammonia was produced as a result of proteolysis. Fermented African locust beans are rich in both protein and fat and feature in the diet of a large proportion of the 200 million people in West Africa.

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The continuous culture performance of a custom designed cell-retention (CR) bioreactor prototype was investigated for the acetone - butanol - ethanol (A-B-E) fermentation by Clostridium acetobutylicum. / A mathematical model for the kinetics of the A-B-E fermentation was developed reflecting the biochemical pathway and culture behaviour. Dynamic and steady-state behaviour of C. acetobutylicum in the CR bioreactor was simulated on the computer and experimentally tested. / In an operational mode with a total cell-retention, a steady-state operation of the bioreactor was predicted up to 52 g/L of sugar in the feed stream. The sugar was completely utilized. Experiments confirmed the suitability of the model and its predictions including the independence of the key process parameter concentrations from the dilution rate. / For the feed sugar concentration in excess of 52 g/L an unsteady-state fermentation system behaviour was predicted by computer simulation and an oscillatory performance of the bioreactor was observed experimentally. Additional bleeding of the whole cell broth from the fermentor resulted in stabilizing the bioreactor performance.