Electronic Thesis and Dissertation Repository


Doctor of Philosophy


Chemical and Biochemical Engineering


Dr. Lars Rehmann


Butanol has long been considered a potential advanced liquid biofuel, in addition to its current application as an industrial solvent. It can be produced biologically; however, the conventional ABE fermentation suffers from many limitations, including low butanol titer, high cost of traditional raw materials, end-product inhibition and high butanol recovery costs. Possible solutions are the use of renewable low-cost feedstocks, genetic manipulations of Clostridia spp. to improve the strains’ butanol titer and tolerance, advanced fermentation techniques, and in-situ product recovery technologies.

In order to overcome some of these limitations, the overall goal of this thesis was to develop a process to produce butanol via fermentation using low-cost feedstocks and integrated product recovery. Jerusalem artichoke tubers and biodiesel-derived glycerol were investigated as potential feedstocks for fermentative butanol production. Pervaporation was evaluated as an online butanol recovery technique and was integrated into the butanol fermentation process.

In the first phase of this research the suitability of Jerusalem artichoke tubers as a renewable feedstock for butanol production was studied and statistical experimental design was used to optimize enzymatic and acid hydrolysis of the feedstock. Both enzymatic and sulfuric acid hydrolysate of Jerusalem artichoke tubers were fermented via solventogenic Clostridia to acetone- butanol- ethanol (ABE). An overall ABE productivity of 0.25 g L-1 hr-1 was obtained from both hydrolysates, indicating the suitability of this feedstock for fermentative butanol production.

In the second phase, the feasibility of butanol production from biodiesel-derived glycerol was investigated. The initial fermentation conditions for butanol production from glycerol were optimized via a central composite design. In the next phase, Jerusalem artichoke hydrolysate and crude glycerol were used as co-substrate for enhanced butanol production. A co-substrate system was characterized and optimized. The optimized conditions were then used for an integrated fed-batch fermentation including pervaporation for in situ butanol recovery. The integrated process achieved a butanol productivity of 0.6 gL-1 hr-1.