Effects of volatile compounds produced by plants on fungal growth and the production of mycotoxins

Fungal contamination of food is one of the most important food safety concerns, however effective techniques to prevent fungal contamination and/or control fungal growth in foods have not yet been established. Some endogenous volatile compounds in plants have antibacterial and/or antifungal activities. For example, when some plants are damaged, they release aliphatic aldehydes with six or nine carbons to protect themselves from microbial infection. Patulin is the major mycotoxin that contaminates apples and apple juice worldwide, and it is regulated in many countries. Patulin has been shown to be immunotoxic and neurotoxic by animal experiments. Many species of Penicillium and Aspergillus produce patulin, but P. expansum is the most typical species responsible for patulin contamination in apples. We attempted to assess the effects of aliphatic aldehydes on P. expansum . Aliphatic aldehydes composed of 3–6 carbons bearing an E double bond at the α -position completely inhibited the fungal growth and suppressed colony formation from spores at relatively low concentrations. On the basis of the structure-activity relationship, the antifungal activity of the compounds is probably attributable to the interaction of the aldehyde group with biological macromolecules. On the other hand, aliphatic aldehydes with 8–10 carbons stimulated patulin production by P. expansum . The results of a reverse transcription-quantitative polymerase chain reaction analysis suggested that the stimulation was partially due to enhanced transcription of some patulin biosynthetic genes. The effects of volatiles of apple on patulin production by P. expansum were also studied. Some volatile compounds, that is, 2-mehtylbutanoic acid and ethyl 2-methylbutanoate, were found to stimulate patulin production. These findings will contribute to the development of new techniques to prevent and control fungal and mycotoxin contamination of foods.