Influence of Major Environmental Parameters on Patulin Production by Penicillium expansum OM1 and Its Growth on Apple Puree Agar Media

Patulin is a mycotoxin produced mainly by <i>Penicillium expansum</i> on apples. <i>P. expansum</i> is a fruit pathogen that can cause apple soft rot. However, much is unknown about the characteristics of <i>P. expansum</i> and influence of major environmental parameters on its patulin production and growth on apple puree agar media (APAM). In this study, we evaluated the influence of pH, temperature, and relative humidity (RH) on patulin production by <i>P. expansum</i> OM1 and its growth (colony diameter and mycelial dry weight) on APAM after isolation and identification of the patulin-producing fungal strain from an apple. The fungal isolate produced the largest quantity of patulin on APAM under 15 °C, pH 4.0, and RH 98%, while it had the highest growth rates on the same media under 25 °C, pH 4.0-6.0, and RH 98%. Our data demonstrated that three important physicochemical factors (pH, temperature, and RH) substantially influenced the patulin production by the fungal species and its growth on APAM. Moreover, our results revealed that patulin was not detected on APAM at 5 °C after 7 days of incubation and that a trace amount of patulin was produced by the fungal strain along with its slow growth on the same media at 5 °C after 14 days. It suggests that patulin contamination by <i>P. expansum</i> on apples could be controlled during postharvest storage below 5 °C. These findings could provide fundamental knowledge for development of efficient strategies to prevent the occurrence of apples contaminated with patulin produced by <i>P. expansum</i> on them during postharvest storage.