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

Abstract Fatty acid esters of fumonisins, namely oleoyl- and linoleoyl esters of fumonisin B 1 (EFB 1 OA and EFB 1 LA, respectively), are modified forms of fumonisins whose 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 mechanism of 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, together with 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 FB 1 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 FB 1 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 FB 1 into fatty acid esters was also shown as strain-related. Results, thus, strongly support the hypothesis that fatty acid esters of FB 1 are produced by the fungus itself at a late stage of growth, or at a certain point of FB 1 accumulation in the medium, using fatty acids from the substrate.