Master of Engineering Science
Chemical and Biochemical Engineering
This work demonstrates lab scale intensification of the fermentation of glycerol to 1-butanol using Clostridum pasteurianum, starting with simulation and comparison of different cell recycle arrangements, development of a cell recycle apparatus with an existing bioreactor, and demonstration of fermentation with the final system. Fermentations performed with the completed system showed that the cell recycle system was not significantly inhibitory to fermentation, and achieved a maximum apparent cell dry weight of 3.14g/L and a maximum butanol productivity of 1.16g/Lh.
Summary for Lay Audience
This thesis covers the development of a system for conversion of glycerol into butanol. The source of glycerol is intended to be crude glycerol, a byproduct of biodiesel production, and butanol can be used as a carbon-neutral replacement for gasoline, which unlike other biofuels does not require mixing or modification for current gasoline engines. To produce butanol from glycerol the bacteria, Clostridum pasteurianum, was used. This organism produces a number of valuable compounds when grown on glycerol, one of which is butanol. These compounds are inhibitory to the organism, which slows fermentation and decreases productivity, so low glycerol concentrations are needed to prevent halting of fermentation. This, however, can result in low productivity, and intensification of the process by cell retention can be used to accommodate this low productivity by increasing dilution rate and thus volumetric productivity. In this case, this was performed using a cell recycle system which retains the cells in the bioreactor while process media can be continuously added and removed. In order to determine the best design of the cell recycle apparatus, simulations were performed and compared, then the system was built, demonstrated on water, and then multiple fermentations were performed demonstrating that the system does in fact intensity fermentation successfully, reaching cell concentrations that in other fermentations required four times greater glycerol concentration, and butanol productivity that in other fermentations required 50% greater glycerol concentration.
Couper, Colin W., "Intensification of Clostridium pasteurianum Fermentation Producing n-Butanol From Glycerol using Microfiltration Cell Recycle" (2020). Electronic Thesis and Dissertation Repository. 7733.
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