Ecophysiology of Penicillium expansum and patulin production in synthetic and olive-based media

Abstract

The olive and its derivatives, in particular olive oil, represent one of the most significant agricultural products in the Mediterranean basin. Storage under inadequate conditions poses serious problems concerning fungal contamination, with consequent defects and potential mycotoxin production in olives and olive oils. Penicillium expansum represents one of the most significant postharvest pathogens in several fruits, including olives. Not only it causes blue mold but also is one of the most relevant patulin (PAT) producing species of the genus Penicillium. The aim of this research was to evaluate the ecophysiological conditions governing growth and PAT production by P. expansum strains previously isolated from Tunisian olives. For this purpose, four P. expansum isolates were tested in a synthetic medium (Czapek Yeast Autolysate, CYA) and in olive-based medium (OM) for their ability to grow and produce PAT under different temperatures (4 ºC, 15°ºC and 25°ºC) for 10 and 20 days. The mycotoxin was analysed by HPLC-UV. Results showed that all isolates were able to grow on tested media at different temperatures. Different PAT production profiles were found, showing that at 25 ºC P. expansum isolates were able to produce PAT on CYA and OM medium. At 15 ºC the production of PAT was only detected on CYA medium, while no PAT production was detected at 4 ºC for the two media.Acknowledgments: The authors are grateful to the Foundation for Science and Technology (FCT, Portugal)