No abstract

The fusarium mycotoxin zearalenone was transformed in cell suspension cultures of Zea mays giving α- and β-zearalenol and the β-D-glu cos ides of zearalenone and α- and β-zearalenol. The structure of zearalenone-4-β-D-glucopyranoside was determined by liquid - chromatography-mass spectrometry and specific hydrolysis with β-glucosidase. α- and β-zearalenol and their glucosides were identified by co chromatography using tic and HPLC and glucosidase - treatment Up to 50% of the mycotoxin added was bound to a non extractable or "bound" residue fraction. After treating this residue by a sequential cell wall fractionation procedure, zearalenone was found to be bound mainly to starch, hemicellulose, and lignin fractions.

To raise the yields for the production of 14C-labelled zearalenone in Fusarium cultures the influence of growth conditions and known effectors or precursors of toxin biosynthesis was studied. Benzoic acid and 2,4-dihydroxybenzoic acid used as precursors decreased toxin formation; in the presence of different pesticides such as 2,4-dichlorophenoxyacetic acid, however, toxin production increased up to 140%. The known pathway of zearalenone biosynthesis could be confirmed from the relative extents of 13C-incorporation into the zearalenone molecule by incubating Fusarium 9raminearum DSM 4529 with D-(+)-[1-~3C]glucose as carbon source. When grown in the presence of D-[U-14C]glucose or [2-~4C]malonic acid the strain produced [14C]zearalenone with specific activities of 0.07 and 0.09 ~tCi/mg, the ~4C-incorporation rates being 0.34% and 0.48%, respectively.