Determination of Patulin Producing Activity and Radiation Sensitivity of Fungi Isolated from Korean Apples

국내산 사과에서 분리한 곰팡이의 패툴린 생성능 및 방사선 감수성 평가

Patulin is a mycotoxin produced by a variety of molds, especially within genera Penicillium, Aspergillus and Byssochlamys growing on various fruits. In this study, patulin producing activities and the effects of a gamma irradiation on the control and/or sterilization of fungal strains isolated from Korean apples, Malus pumila var. dulcissima, were evaluated. Nine fungal strains; five strains of genus Penicillium and one strains of genus Glomerella, Giberella, Alternaria and Galactomyces were isolated and identified by the similarity analysis based on the nucleotide sequence of the ITS5-5.8S-ITS4 region. Among the isolated strains, four Penicillium strains and a Glomerella showed patulin producing activities. The maximal patulin-producing activity of P. griseofulvum ATCC 46037, a standard strain of patulin-producing fungi, was 1,211.5 ppm in a 5-GYEP broth medium, while those of the isolated fungi reached to 27.4~134.2 ppm. Patulin-producing levels were dependent on the carbon sources and maximal production of the patulin by P. griseofulvum, P. crustosum, I-3, I-6, I-7 and I-8 was observed in a broth media containing glycerol, fructose, glycerol, glucose, lactose and fructose, respectively. The D₁₀-values of the conidia of tested strains in an aqueous suspension were calculated in the range of 0.25~0.64 kGy. In conclusion, although the patulin producing activities of the isolated fungi were significantly lower than those of standard strains, it cannot deny the possibility of an patulin contamination of the Korean apples. Therefore, gamma ray irradiation (1.0 kGy) after harvest of apples could be applied to prevent the growth of a patulin producing molds for a safe distribution.