Method for Identifying Heat-Resistant Fungi of the Genus Neosartorya

Abstract

Species of the genus Neosartorya are heat-resistant fungi that cause the spoilage of heat-processed acidic foods due to the formation of heat-resistant ascospores, and they produce mycotoxins, such as fumitremorgins and gliotoxin. Their anamorphs are phylogenetically and morphologically very close to Aspergillus fumigatus, which has never been reported as a spoilage agent in heat-processed food products. Therefore it is important to discriminate between the species of Neosartorya and A. fumigatus in the food industry. In the present study, we examined β-tubulin and calmodulin genes to identify Neosartorya and A. fumigatus at the species level and found a region for specifically detecting these species. We succeeded in developing the PCR method of differentiating and identifying Neosartorya and A. fumigatus using specific primer sets. Moreover, we developed specific primer sets to identify Neosartorya species, N. fischeri, N. glabra, N. hiratsukae, N. pseudofischeri, and N. spinosa–complex, which are important in food spoilage; these fungi vary in heat resistance and productivity of mycotoxins, depending on the species. PCR using these primer sets did not detect other fungi involved in food spoilage and environmental contamination. These identification methods are rapid and simple with extremely high specificity.