Arginine acts as an inhibitor of the biosynthesis of several mycotoxins

• Amino acids have a profound influence on ochratoxin biosynthesis by Penicillium.
• Arginine inhibits the biosynthesis of several mycotoxins under certain conditions.
• Urea, a catabolic metabolite of arginine, also has inhibiting activities.
• Arginine inhibits ochratoxin biosynthesis also under food related conditions.

It is well known that the type and the availability of nitrogen have a great influence on the biosynthesis of certain mycotoxins. Here it is shown that some amino acids have no influence, some others strongly support and a third group inhibits the biosynthesis of ochratoxin (OTA) by Penicillium nordicum even in a complex medium, such as PDA. Arginine (Arg) is one of the strong OTA inhibiting amino acids. It was shown that Arg not only inhibits OTA in Penicillium but also citrinin (CIT) biosynthesis in Penicillium verrucosum, Penicillium expansum and Penicillium citrinum and alternariol (AOH), alternariol monomethylether (AME) and tenuazonic acid (TeA) biosynthesis in Alternaria alternata. The minimal inhibitory concentration of Arg differs depending on the mycotoxin and the species analysed. However, the OTA biosynthesis by P. verrucosum and P. nordicum was most sensitive. Growth, on the other hand, was much less affected by Arg. Urea, a metabolite of Arg catabolism, shows a similar inhibitory activity. In wheat medium containing 50 mM Arg almost no OTA was produced by Penicillium, in contrast to plain wheat medium.