The process of adding carbohydrates to proteins, called glycosylation, is the most universal and structurally diverse form of posttranslational modification, it being shared by the vast majority of organisms all the way to humans themselves. This process is important for cells in a lot of ways, be it protein stability, secretion or localization. In fungi, glycobiology has been investigated for two main reasons: first, using fungi as model organisms, and second, trying to engineer them into expression systems for recombinant proteins. For the human pathogen Aspergillus fumigatus, an opportunistic, saprophytic fungus that has continuously been gaining importance as a disease agent over the past decades, the possible significance of protein glycosylation for its virulence is another factor that warrants more research. .The glycobiology of A. fumigatus has been one focus of research in the lab of Professor Cheng Jin for a lot of years, and major advances have been made identifying key enzymes and characterizing their molecular function. This work aims to further this knowledge, by overexpressing five central glycosylation enzymes in an attempt to functionally characterize these enzymes from a novel point of view. This genetic approach especially allows for an investigation of the possible interplay of different glycosylation components, as several enzymes can be overexpressed simultaneously, thus making a deeper understanding of the complexity of this system possible. Eventually, the results of this work might not only shed a brighter light on the role of protein glycosylation during the A. fumigatus infection process, but they may also provide cues for the improvement of biotechnologically relevant Aspergilli strains.