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Exploring alternative feedstocks and engineering butanol tolerance to optimise biofuel production by Clostridium saccharoperbutylacetonicum

Yap, Fei Ying (2018) Exploring alternative feedstocks and engineering butanol tolerance to optimise biofuel production by Clostridium saccharoperbutylacetonicum. Master of Research (MRes) thesis, University of Kent,. (KAR id:73444)

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Abstract

Acetone-butanol-ethanol (ABE) fermentation is an established industrial process that uses Clostridium bacteria for the conversion of plant-derived 'feedstocks' into solvents (acetone, butanol and ethanol) that can be used as biofuels. These solventogenic clostridial strains are naturally adapted to access energy/carbon from complex sugars found in common feedstocks made from corn and rice, but it is of interest to explore a variety of waste biomass to provide a stable supply of feedstock for industrial biofuel production. It was of particular interest to investigate microalgae as a feedstock for ABE fermentation: microalgae are currently used by project partners Algaecytes® to produce Omega 3, which results in large amounts of low-value spent biomass following product extraction. In this study, commercially-available Chlorella vulgaris was used as well as a Eustigmatophyceae proprietary strain obtained from the project partner. Feedstocks were processed in a variety of ways and fermentations were performed in serum bottles and 500 mL fermenters to optimise optical detection of clostridial growth and solvent production. The highest solvent yield of 3.27 g/L (acetone: 0.40 g/L; butanol: 1.40 g/L; ethanol: 1.47 g/L) was achieved with non-autoclaved and non-centrifuged 10 % Eustigmatophyceae spent biomass supplemented with 1 % glucose, whereas a 10 % feedstock of C. vulgaris supplemented with 1% glucose had a lower yield of 1.20 g/L (acetone: 0.20 g/L; butanol: 1.00 g/L). These yields are significantly lower than those obtained with industrial feedstocks (in excess of 20 g/L) where butanol toxicity becomes limiting, so further work will be necessary to refine the use of algal biomass as a feedstock.

In addition to investigation of alternative feedstocks, there is clear biotechnological value in producing a Clostridium strain with increased butanol tolerance. Previously, overexpression of the FocA formate transporter has been shown to enhance butanol tolerance in Escherichia coli. Cloning/overexpression of E. coli focA and the clostridium homologue fdhC were done, with the aim of generating a butanol-tolerant strain of C. saccharoperbutylacetonicum. This work has the potential to generate higher solvent yields that could improve process economics for industrial biofuel production by ABE fermentation.

Item Type: Thesis (Master of Research (MRes))
Thesis advisor: Shepherd, Mark
Uncontrolled keywords: Acetone-butanol-ethanol fermentation, Clostridium, Clostridium saccharoperbutylacetonicum, microalgae, Chlorella vulgaris, Eustigmatophyceae, biofuel
Divisions: Faculties > Sciences > School of Biosciences
SWORD Depositor: System Moodle
Depositing User: System Moodle
Date Deposited: 10 Apr 2019 09:31 UTC
Last Modified: 23 Jan 2020 04:16 UTC
Resource URI: https://kar.kent.ac.uk/id/eprint/73444 (The current URI for this page, for reference purposes)
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