Degree Name

Master of Science (MS)

Semester of Degree Completion

Summer 2019

Thesis Director

Thomas Canam

Thesis Committee Member

Yordan S. Yordanov

Thesis Committee Member

Eloy Martinez

Abstract

Traditional physicochemical and physicomechanical pretreatment technologies have improved the deconstruction of lignocellulose, but often require high energy inputs and added chemical reagents. Recent studies have demonstrated the use of white-rot fungi as alternative biological pretreatment agents that can mitigate these concerns. Although, white-rot fungi have been shown to grow on a variety of non-woody substrates, they have not been explored with respect to sunflower, which has the potential to provide raw materials for both biodiesel and bioethanol. In the present study, Silverleaf sunflower stems (Helianthus argophyllus) were used as substrates for the white-rot fungi Phanerochaete chrysosporium and Trametes versicolor, and the transcriptome response by these fungi to sunflower stems was explored after six weeks of growth. Those genes that were more highly expressed on sunflower stems compared to malt extract medium were determined at the 25X and 10 X thresholds. At the 25X threshold there were 102 transcripts for P. chrysosporium and 144 transcripts for T. versicolor, while at the 10X threshold there were 412 transcripts for P. chrysosporium and 326 transcripts for T. versicolor. The majority of these transcripts were, as expected, directly tied to lignocellulose deconstruction, such as peroxidases, oxidases, and glycoside hydrolases. Transporters are not directly involved in lignocellulose breakdown, however they made up 24% and 10% of characterized transcripts at the 25X threshold for P. chrysosporium and T versicolor, respectively. In addition, 75% and 37% of transcripts at the 25X threshold for P. chrysosporium and T. versicolor, respectively, were classified as hypothetical or unknown, which further highlights the need for improved functional characterization of enzymes from these two fungi.

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