Improvement of Biofuel Fermentation Processes With Use of Poly(vinyldodecylimidazolium bromide) for In-situ Product Removal
Loading...
Authors
Vincent, Rachel
Date
Type
thesis
Language
eng
Keyword
n-butanol , Clostridium acetobutylicum , in-situ product removal , polyionic liquids , fermentation , two-phase partitioning bioreactor , biofuels
Alternative Title
Abstract
The production of biofuels through fermentation has become increasingly important due to the need for sustainable energy sources. The fermentation processes of ethanol and n-butanol, by Saccharomyces cerevisiae and Clostridium acetobutylicum, respectively, suffer from end-product inhibition, hindering final product concentrations, volumetric productivity, and product recovery. To alleviate these limitations, in-situ product removal (ISPR) methods can be implemented, via two-phase partitioning bioreactor (TPPB) technology. This work used a polyelectrolyte absorbent phase, poly(vinyldodecylimidazolium bromide) [P(VC12ImBr)], in TPPB systems for the removal of the target molecules, ethanol and n-butanol, with focus on the latter due to more severe product inhibition and its greater promise as a biofuel.
P(VC12ImBr) was synthesized and characterized for ISPR implementation and was found to have a partition coefficient (PC) and selectivity of 1.1 and 7.2 for ethanol, and a PC of 6.5 and selectivity of 46 for n-butanol. Characteristics of P(VC12ImBr) were found to be favorable for TPPB implementation, including its density, diffusivity for n-butanol, and complete biocompatibility with S. cerevisiae and C. acetobutylicum. A differential scanning calorimetry (DSC) scan of P(VC12ImBr) found its melting temperature to be -17°C and a glass transition temperature above 200°C, which can be reduced by plasticization with water. Anion exchange between bromide in P(VC12ImBr) and sulphate and phosphate ions in fermentation medium was observed, however this did not affect its PC or selectivity.
When implemented in ethanol and acetone-butanol-ethanol (ABE) ISPR fermentations, P(VC12ImBr) absorbed target molecules from the fermentation broth, however improvements relative to a control were observed only for the ABE fermentation with the mass fraction of sorbent used. In the ABE ISPR fermentation there was greater substrate conversion and an increase in volumetric productivity of 76%.
The water + n-butanol + P(VC12ImBr) ternary system confirmed P(VC12ImBr)’s preference for n-butanol by concentrating dilute solutions above its aqueous solubility limit. To examine n-butanol absorbed by P(VC12ImBr), a 1.5 wt% n-butanol solution was concentrated to 25 wt% n-butanol, which was thermally removed and condensed to show phase separation. The ability of P(VC12ImBr) to concentrate dilute solutions of n-butanol above its solubility limit would allow for an improved n-butanol purification process.
Description
Citation
Publisher
License
Queen's University's Thesis/Dissertation Non-Exclusive License for Deposit to QSpace and Library and Archives Canada
ProQuest PhD and Master's Theses International Dissemination Agreement
Intellectual Property Guidelines at Queen's University
Copying and Preserving Your Thesis
This publication is made available by the authority of the copyright owner solely for the purpose of private study and research and may not be copied or reproduced except as permitted by the copyright laws without written authority from the copyright owner.
ProQuest PhD and Master's Theses International Dissemination Agreement
Intellectual Property Guidelines at Queen's University
Copying and Preserving Your Thesis
This publication is made available by the authority of the copyright owner solely for the purpose of private study and research and may not be copied or reproduced except as permitted by the copyright laws without written authority from the copyright owner.