Identification and Characterization of Fungi Isolated from a Cheese Cave in the Eastern United States

Abstract

Fungal spores are ubiquitous in indoor air, with the diversity of species geographically variable. Species present depend upon outdoor sources, physical conditions of the built environment, and human use of the built environment. Cheese is a microbial product produced through inoculation of milk with specific fungal and bacterial cultures. Indigenous fungi can also impact cheese flavor and quality. While there are studies investigating the microbiome of cheese and starter cultures, there are not many studies investigating the airborne fungal community in cheese caves. This study investigated the viable airborne fungi present in a man-made cheese cave in the Eastern United States. Fungi were captured passively on both general culture media and milk-based media using the open plate method. Thirty-one isolates were identified to genus by sequence of the nuclear ribosomal internal transcribed spacer (ITS) region. Most of the isolates were cheese-associated taxa: Penicillium (26 isolates) and Scopulariopsis (1 isolate). The only other taxon identified was Cladosporium (4 isolates), which is commonly isolated in surveys of both indoor and outdoor air and has been isolated from cheese. The airborne Penicillium-Fasciculata isolates captured from the cheese cave exhibit growth traits (conidiation, increased growth on malt extract media, and loss of casein hydrolysis) more similar to wild Penicillium fungi than the domesticated commercial cheese strain Penicillium candidum.