Fungal production of biofuel and flavor compounds in liquid and solid state
Schoen, Heidi Renee
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Oil reserves are limited, so new sources of fuels and petroleum byproducts must be found. Some endophytic, filamentous fungi produce fuel and flavor relevant compounds from minimally pretreated cellulosic materials. Additionally, fungal volatile organic compounds can act synergistically as mycofumigants to inhibit bacteria, insects, and fungi. This dissertation identifies and quantifies fungal volatile organic compounds. A new method was created to quantify the total volatile organic carbon in the gas phase. A platinum catalyst was used to completely oxidize organic compounds to carbon dioxide, which was then measured with a carbon dioxide detector. This method agreed to within 94% of volatile organic carbon measurements taken with proton transfer reaction-mass spectrometry. Additionally, fungal production of fuel and flavor relevant volatile organic compounds was measured with varying pH and temperature in liquid cultures from Nodulisporium isolates EC, CO and TI. Production was also measured for TI when grown in solid state on the agricultural byproduct beet pulp at varying oxygen conditions. Finally, the model volatile organic compound producing organism Ascocoryne sarcoides was grown in liquid state with varying nitrogen sources, including amino acids. The three Nodulisporium isolates produced longer carbon number compounds at lower temperatures, which are better biofuels and are more likely to be bioactive. This trend was especially strong among volatile organic compounds associated with fatty acid metabolism. The fungi produced fewer compounds at lower pH. In solid state, TI had the highest total production of ethanol and carbon number four and higher compounds under anoxic conditions, but the highest production rates under microaerophilic conditions. Additionally, ethanol appeared to be the only major anoxic fermentation byproduct. Finally, A. sarcoides produced the most ethanol and carbon number four and higher compounds in the gas phase with ammonium chloride as the nitrogen source. Nitrogen sources that are reactants for volatile organic compounds, like leucine and phenylalanine, had lower gas phase concentrations of volatile organic compounds.