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Date of Award

2015

Document Type

Campus Access Dissertation

Degree Name

Doctor of Philosophy in Biochemistry and Molecular Biology (PhD)

Administrative Home Department

Department of Biological Sciences

Advisor 1

Rupali Datta

Committee Member 1

Dibyendu Sarkar

Committee Member 2

Ramakrishna Wusirika

Committee Member 3

Susan Bagley

Committee Member 4

Victor Busov

Abstract

Existing heavy metal contaminated marginal land is often the result of historical mineral mining practices. Concerns with the elemental toxicity of these contaminants extend to environmental and organismal health. Re-purposing this unusable land for second-generation lignocellulosic crop acreage while immobilizing and remediating the metal contaminated soil was proposed. The multitasking capability of two lignocellulosic species was examined in three parts. One species evaluated, miscanthus (Miscanthus giganteus), is a current bioethanol feedstock, which was evaluated for its ability to be cultivated on copper loaded soil and its phytoremediation potential. The other species evaluated, vetiver grass (Chrysopogon zizanioides L. Nash), is known hyperaccumulator of many xenobiotics, but was studied specifically for its ability to remediate copper and its potential as a novel second-generation lignocellulosic feedstock. First, the two lignocellulosic species were used to investigate their resilience to cultivation on copper contaminated soils, their capacity to perform phytoremediation—specifically phytostabilization, and the effects of copper exposure on their lignocellulosic composition for downstream impact on fermentation. Miscanthus and vetiver performed phytostabilization of copper successfully with little phytotoxicity and altered lignocellulosic compositions when grown in the presence of copper loaded soil. Secondly, the sequential processes for the conversion of lignocellulosic biomass to ethanol were optimized for each species to maximize ethanol production using response surface methodology (RSM). Dilute acid pretreatment of both feedstocks was optimized to maximize the solubilization of hemicellulosic sugars, while maintaining fermentation inhibitor (furfural, 5-hydroxymethylfurfural, and acetic acid) concentrations below their respective inhibitory concentrations. Enzymatic saccharification was optimized to achieve maximum glucose recovery from the cellulosic fraction of the biomasses. Fermentation was optimized to yield maximum ethanol concentrations. Lastly, the impact of vetiver and miscanthus biomass harvested from copper loaded soils on ethanol production was investigated. Vetiver biomass harvested from copper contaminated soils produced significantly greater amounts of ethanol using the RSM optimized processes than vetiver biomass harvested from control soil. Miscanthus biomass produced less ethanol when harvested from copper loaded soil than control soil. Both vetiver and miscanthus grass are suitable candidates as lignocellulosic second-generation bioethanol feedstocks that can be cultivated on copper contaminated marginal land, while performing phytostabilization.

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