Aspergillus niger is a fictional microbiology-themed character in Moyashimon, representing a species of black mold used in fermentation and industrial processes. In the series, this character appears as one of the anthropomorphized microorganisms that the protagonist can see and communicate with. Aspergillus niger helps illustrate the show’s educational focus on fermentation, microbes, and food science, while also adding personality and humor to the cast of tiny, talking organisms.