Phenotypic Characterization of Wild-Type and Food-Associated Aspergillus

Aspergillus is a genus of filamentous fungi comprising approximately 250 unique species found in a variety of niches within human food environments, ranging from beneficial fermentation to detrimental mycotoxin production. The genus is wide ranging and amenable to growth on various carbon sources, finding niches within many ecosystems in critical biodeterioration roles. Aspergillus oryzae and Aspergillus flavus exhibit strong genetic similarity up to 99.5% yet diverge remarkably in their phenotypic expression. This thesis explores the phenotypic markers of closely related dyads of food-associated and wild Aspergillus species, focusing on enzymatic activities, growth patterns and organoleptic quality characteristics. In evaluating these characteristics, distinct phenotypic profiles emerged. Aspergillus oryzae strains exhibit significant alpha-amylase activity, indicative of adaptation to starch-rich environments such as those found in sake production. Aspergillus flavus displays weak enzymatic activity but strong growth across substrates. While there is broad overlap in the volatolome of both Aspergillus species, A. oryzae exhibits significantly more variety and greater quantity of unique volatile organic compounds, many of which can engender favorable sensory characteristics to fermented foods. These phenotypic specializations underscore the adaptive responses of Aspergillus species to human foodways. Moreover, the findings suggest potential implications for industrial applications and offer insights into the adaptation of fungal species into unique human food environments.