Author

Eric Stevens

Date of Award

2015

Document Type

Thesis

Department

Chemistry

Thesis Advisor

Arthur J. Stipanovic

Keywords

bio-fuels, transportation fuel, C. acetobutylicum

Abstract

Butanol is a potential transportation fuel which could eventually replace fossil- derived petroleum and transition the world towards a more sustainable future. This fuel can be produced by enzymatically hydrolyzing pretreated lignocellulosic biomass, and simultaneously fermenting the resultant sugars with specific bacterial strains. In this experiment switchgrass was chemically pretreated in a 75% (v/v) ethanol and 1% H2SO4 (1% v/v) solution and subjected to simultaneous saccharification and fermentation (SSF) with hydrolytic enzymes and Clostridium acetobutylicum. The pH control method for the SSF apparatus was varied between a 50 mM acetate buffer solution (HOAc), and the addition of calcium carbonate (CaCO3) powder. Cellular products were quantified by HPLC analysis, and results were compared to identical procedures conducted on microcrystalline cellulose. The microcrystalline cellulose SSF procedures yielded 4.33 g/L (HOAc) and 4.27 g/L (CaCO3) of butanol, with 0.037 g/L/min (HOAc) and 0.038 g/L/min (CaCO3) butanol production rates. No butanol was produced from switchgrass, regardless of the pH control method. Butyric acid, the chemical precursor to butanol, was produced from switchgrass samples however, which suggests the final conversion step to butanol was most likely hindered. It is believed that the pH levels of the switchgrass SSF apparatuses were unsatisfactory, or that the acid-pretreated biomass released inhibitory compounds which prevented the biosynthesis of butanol.

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