Graduate Program

Biological Sciences

Degree Name

Master of Science (MS)

Semester of Degree Completion

Fall 2021

Thesis Director

Thomas Canam

Thesis Committee Member

Eloy Martinez

Thesis Committee Member

Gopal R. Periyannan

Abstract

Plant biomass is considered to be an important future starting material for fuels and chemicals, thereby decreasing our reliance on fossil fuels. While direct combustion continues to be a source of fuel, the generation of liquid fuels from plant biomass for transportation has proven to be challenging. Among the limiting factors for conversion of this material to biofuels is the recalcitrant nature of lignocellulose, the primary component of non-starch plant biomass. A strategy to overcome this dilemma is to directly or indirectly use the enzymes from white-rot fungi, which have evolved a unique ability to deconstruct lignocellulose. However, the biochemical mechanisms responsible for this ability are not entirely clear, nor is the reaction of these fungi to different forms of biomass. The primary goal of this research was to analyze the response of two white-rot fungi, P. chrysosporium and T. versicolor, to maple wood, miscanthus straw, and sunflower stems, using existing transcriptome datasets. Among the findings were core sets of 26 and 32 transcripts that were highly expressed (30X threshold) on all three types of biomass by P. chrysosporium and T. versicolor, respectively. As anticipated, these core sets included a variety of protein categories involved with lignocellulose deconstruction, such as cytochrome P450, lignin peroxidase, glycoside hydrolase, manganese peroxidase, endoglucanase, and cellobiohydrolase. The analyses also revealed high percentages of transcripts in the core sets that coded for uncharacterized proteins, with 17 transcripts (65%) for P. chrysosporium and 6 transcripts (19%) for T. versicolor. To assist with future efforts to elucidate the function of the six uncharacterized proteins from the T. versicolor core set, the coding regions were cloned into the yeast expression plasmid pYES-DEST52. The S. cerevisiae strain INVSc1 was then transformed with these vectors for expression of the uncharacterized proteins under the inducible GAL1 promoter. Future completion of the core set of transcripts from T. versicolor will allow for a more thorough understanding of the biochemistry involved with the breakdown of lignocellulose, which could be leveraged for biomass-to-biofuel conversion strategies.

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