Doctor of Philosophy (PhD)


School of Nutrition and Food Sciences

Document Type



With an unpredictable market for gasoline and increased concerns with the pollution created by burning fossil fuels, there is a push for developing suitable replacements for gasoline. While corn-based ethanol production is the most common renewable biofuel produced in the United States, ethanol is not an ideal solution to gasoline replacement due to low energy density, hygroscopic and corrosive properties and inability to purify by distillation alone. Higher alcohols such as butanol do not have the same problems with energy density, purification and hygroscopic and corrosive properties. The fermentation of butanol by using solventogenic Clostridium species, creating acetone, butanol and ethanol (known as ABE fermentation) is one of the world’s oldest industrial fermentations. Since butanol is toxic to Clostridium species at a concentration of only 13 g/L, traditional batch fermentation of butanol with steam stripping distillation is currently not as economical as fermentation and distillation of ethanol. Fermentation using glucose produced higher solvent outputs, rates of productivity and yields than fermentations using sugarcane products as substrates. Butanol and total solvent production using glucose as a substrate averaged 7.2 (+/- 0.7) g/L and 11.2 (+/- 0.9) g/L, respectively. Fermentation using sugarcane molasses and sugarcane juice as substrates produced 6.5 g/L butanol and 9.7 g/L total solvents and 3.1 g/L butanol and 4.0 g/L total solvents, respectively. Production of butanol was increased to 9.1 g/L in a fermentation of glucose when soy oil was used as a coextractant. Fermentations in which the pH dropped below 4.80 showed decreased solvent production and the pH was unable to rise in the same manner as other fermentations. The acid crash was exhibited in several batch fermentations as well as continuous fermentation using an immobilized culture of C. beijerinckii optonii. The acid crash resulted in lowered solvent production, low pH and physiological differences in the cells in the culture. Fermentation using immobilized culture produced a maximum 5.4 g/L butanol and 6.8 g/L total solvents at a dilution rate of 0.18 hr-1 and 25 g/L initial glucose. Higher glucose levels and different dilution rates gave lower butanol and total solvent productions.



Document Availability at the Time of Submission

Release the entire work immediately for access worldwide.

Committee Chair

Day, Donal

Included in

Life Sciences Commons