Oleoyl and linoleoyl esters of fumonisin B1 are differently produced by Fusarium verticillioides on maize and rice based media

Fatty acid esters of fumonisins, namely oleoyl- and linoleoyl esters of fumonisin B1 (EFB1OA and EFB1LA, respectively), aremodified forms of fumonisinswhose formation and occurrence have been reported so far in naturally infected maize and in artificially inoculated rice. There is a lack of knowledge about the mechanismof formation, mainly in relation to the role played by the substrate. Therefore, in this work we studied the dynamics of accumulation of the toxin and its esters, togetherwith their precursor, in maize and rice based media inoculated with different strains of F. verticillioides and incubated at 25 °C for 7–45 days. The production pattern of FB1 and its modified forms was significantly influenced by growth media, reaching a higher concentration in cornmeal compared to rice based medium. Similarly, cornmeal was more supportive for the conversion of FB1 by considering the esterification rate, with a prevalence of linoleoyl esters compared to oleoyl esters resembling the OA/LA rate in both media. The conversion of FB1 into fatty acid esters was also shown as strain-related. Results, thus, strongly support the hypothesis that fatty acid esters of FB1 are produced by the fungus itself at a late stage of growth, or at a certain point of FB1 accumulation in themedium, using fatty acids fromthe substrate.