Date of Award

12-2015

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Legacy Department

Environmental Engineering and Science

Advisor

Finneran, Kevin T.

Committee Member

Henson, J. M.

Committee Member

Freedman, David L.

Committee Member

Walker, Terry H.

Abstract

The volatility of foreign and domestic petroleum markets has prompted initiatives for the development of alternative liquid energy carriers which have the capacity to accommodate our current transportation infrastructure. Butanol, which has an energy density similar to that of gasoline and can be produced through the fermentation of carbohydrates by solventogenic Clostridia, has been investigated as a supplement or direct replacement to gasoline. However, most butanol fermentations rely on glucose as a feedstock which is in direct competition with our food supply, and this requires the exploration of alternative fermentable substrates. This study investigates the use of electrochemical fermentation modifications as “drop-in” strategies to stimulate bacterial solventogenesis (butanol) and the consumption of xylose, which is the second most abundant sugar contained within lignocellulosic biomass. Monoculture, solventogenic Clostridia and mixed consortia were challenged with electron shuttling compounds and/or a terminal electron acceptor in the form of ferric iron or solid state graphite electrodes. Results from this study indicate that electron shuttling to ferrihydrite stimulates concomitant increases in metabolite production and xylose consumption for both pure and mixed culture fermentations in which xylose was utilized as the sole fermentable substrate. Mediatorless electrochemical stimulation of solventogenesis and xylose consumption was observed in fermentations challenged with an economical, solid-state graphite electrode system. Data presented within this study indicate that extracellular electron transport to terminal electron acceptors has a global, favorable effect on fermentative bacterial metabolism.

Share

COinS