Detection of Fungal Contamination on Museum Books Stored under Controlled Environmental Conditions: A Discrepancy Between Culture-Based and Metagenomic Analysis Approaches

Mold contamination in library and museum collections poses risks to both cultural heritage and human health. This study examined fungal flora on books stored under controlled environmental conditions (temperature <20 °C, relative humidity <50%) in The University Museum, The University of Tokyo. Both culture-dependent methods and DNA-based metabarcoding targeting the internal transcribed spacer 2 region were used. DNA analysis revealed that Aspergillus halophilicus accounted for over 90% of the sequences from six books. In contrast, culture-based methods using standard media (e.g., PDA, DG18, M40Y) primarily isolated species such as Aspergillus, Penicillium, and Cladosporium, but not A. halophilicus. However, cultivation on CzA supplemented with 70% sucrose at lower temperatures enabled successful isolation of A. halophilicus from one sample. The strain was identified based on morphological features and β-tubulin gene analysis. These findings demonstrate a notable discrepancy between molecular and culture-based results, underscoring the limitations of conventional media for detecting xerophilic fungi in dry environments. The study suggests that desiccation-tolerant species like A. halophilicus can thrive even under strict storage controls and may evade standard integrated pest management (IPM) protocols. To better assess fungal risks in preservation settings, combining improved media with DNA-based methods is essential.