Doctor of Philosophy
Chemical and Biochemical Engineering
Dr. Dimitre Karamanev
Dr. Argyrios Margaritis
In this thesis, biobutanol production by biological fermentation was investigated from the corn plant, integrating two approaches. The first one was to utilize corn cobs, a cellulosic-based material. The second, using a new sugar-based material, sugarcorn juice. Utilizing suitable Clostridia strains for each substrate, these approaches converged into a biorefinery concept to produce renewable biofuels in Ontario, Canada. The corn cob pretreatment was carried out by a dilute acid method resulting in temperature as the variable with most significant effect towards glucose liberation. The enzymatic hydrolysis was performed utilizing a very low concentration of an enzymatic stock solution with approximately 44% of hydrolysis conversion. Biobutanol fermentation was pursued utilizing a Clostridium beijerinckii strain and cellulosic biobutanol was produced in a concentration of 4.42 g L-1 at 48h with 97% of reducing sugars utilization.
Different ABE fermentations by Clostridium saccharobutylicum ATTC BAA-117 using glucose, fructose, sucrose, and a mix of them, resulted in butanol production as high as 12-14 g L-1. For the first time, sugarcorn juices from Canadian corn hybrids, were characterized and proven as a suitable medium for biobutanol production. Variation in sugar composition of sugarcorn juices across different hybrids and growth seasons were observed during this study, from 102 g L-1 to 145 g L-1, with fructose, glucose and sucrose accounting for about 80%.
Clostridium beijerinckii 6422 produced 8.49 g L-1 of butanol over 257h of fermentation utilizing sugarcorn juice as substrate. It had a biphasic fermentation where acids accumulation happened at the beginning of fermentation. Interestingly, at the end of the fermentation butyric acid was reactivated and the butanol production shifted towards butyric acid production. Clostridium saccharobutylicum produced 11.05 g L-1 of butanol over 227 h of fermentation utilizing sugarcorn juice as substrate. Both strains could utilize sucrose, fructose and glucose concomitantly. There is enough evidence to agree that Clostridium saccharobutylicum has a PTS-sucrose system which allows the cell to transport sucrose inside the cell.
The proposed Canadian sugarcorn (CANSUG) biorefinery can commercially generate biofuels and biochemicals while limiting wastes, offer environmental benefits to the energy sector, and strengthen the Canadian bio-economy.
Gomez-Flores, Reyna, "Biobutanol production from cellulosic and sugar-based feedstock from the corn plant" (2018). Electronic Thesis and Dissertation Repository. 5369.
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