Increasing fermentative butanol production in Clostridium beijerinckii using oxidized extracellular electron shuttling molecules

Haluska, Anne

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https://hdl.handle.net/2142/15987 Copy

Description

Title

Increasing fermentative butanol production in Clostridium beijerinckii using oxidized extracellular electron shuttling molecules

Author(s)

Haluska, Anne

Issue Date

2010-05-18T18:53:29Z

Director of Research (if dissertation) or Advisor (if thesis)

Finneran, Kevin T.

Department of Study

Civil & Environmental Eng

Discipline

Environ Engr in Civil Engr

Degree Granting Institution

University of Illinois at Urbana-Champaign

Degree Name

M.S.

Degree Level

Thesis

Keyword(s)

• Clostridium beijerinckii
• 1-5mM anthraquinone-2,6-disulfonate (AQDS)
• butanol
• fermentation

Abstract

Continuing concerns over dependence on foreign oil and the environmental impacts of using oil as a major source of fuel have led to increased interest in more sustainable energy options. Bio-butanol, produced during fermentation of plant biomass, is one possible alternative. However, yields for butanol fermentation are low making recovery difficult. Higher yields are needed to make butanol a competitive option for an alternative fuel source. This research focuses on using extracellular electron shuttles to alter the metabolic pathways in Clostridium beijerinckii NCIMB 8052 fermentation to increase butanol yield with glucose as a primary substrate. 1-5mM anthraquinone-2,6-disulfonate (AQDS), the oxidized form of the electron shuttle, were introduced into batch cultures of C. beijerinckii and increased butanol yields by 2.5 to 5 times relative to glucose alone fermentation batches. An electron mass balance of the system indicated that butyric acid equivalents decreased as butanol equivalents increased. Adding 20 mM Fe(III) (as ferrihydrite or ferric citrate), which also acts as an electron sink, increased butanol yield by 5 times relative to the glucose-only control. Adding both 1 mM AQDS and 20 mM Fe(III) increased the yield up to 5.5 times relative to the glucose-alone control, for a yield of 0.37 and final butanol concentration of 90 mM. The increase in butanol yield with Fe(III) is due to the fact that when AQDS is reduced, the hydroquinone immediately transfers electrons to the Fe(III) thus recycling the AQDS so that it can be reduced again. We anticipate that this strategy can be used to increase commercial bio-butanol yield, as well as provide insight into how fermentative metabolism can be modulated. Addition of 60mM supplementary acetate increased butanol yields 2.1 times compared to glucose-only control. 1mM AQDS and 60mM acetate increased butanol yields 2.27 times relative to the glucose controls. Adding 20mM ferric iron to cultures containing 60mM acetate decreased butanol yields compared to cultures amended with acetate but without ferric iron.

Graduation Semester

2010-5

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http://hdl.handle.net/2142/15987

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Copyright 2010 Anne Haluska

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