Zearalenone [6-(10-hydroxy-6-oxo-trans-1-undecenyl)-β-resorcylic acid lactone] is biosynthesized by Fusarium roseum by head-to-tail condensation of acetate units via the acetate-malonyl-CoA (polyketide) pathway. Incorporation and distribution of 1-[14C]acetate into zearalenone was demonstrated by degradation of the molecule into the aromatic ring, CO2, oxalic, succinic and glutaric acids. Incorporation and distribution of 1-[13C]acetate and 1,2-[13C]acetate was demonstrated by 13C-NMR and confirmed the conclusion reached by 14C-incorporation studies. CO2 is rapidly fixed by cultures of F. roseum, presumably by phosphoenolpyruvate carboxykinase and pyruvate carboxylase and incorporated into zearalenone. The wild-type isolates of F. roseum normally produce optimum amounts of zearalenone on a solid medium such as rice and at lower temperatures (10–14 C), although mutants are available that produce copious amounts in liquid medium. Some wild-type isolates also produce zearalenone optimally at 20–25 C.
1Scientific Journal Series Paper No. 10,960, Minnesota Agricultural Experiment Station. This research was supported in part by a U.S. Public Health Service Research Grant 2RO1-FD-00035.