SWAINSONINE PRODUCTION BY METARHIZIUM-ANISOPLIAE DETERMINED BY MEANS OF AN ENZYMATIC ASSAY

An enzymatic assay for the indolizidine alkaloid swainsonine in culture supernatants of Metarhizium anisopliae is described. The assay relies on the potent and specific inhibition of jack bean cc-mannosidase by low concentrations of this metabolite. A calibration curve was obtained by plotting the ratio of enzyme activities in the absence and presence of swainsonine against swainsonine concentration. The assay was suitable for concentrations of swainsonine up to 0.5 mu g ml(-1). Production of swainsonine by fermenter cultures of M. anisopliae in Czapek-Dox medium was followed using this assay procedure. The onset of swainsonine production under oxygen limitation followed a drop in pH of the culture. Addition of the biosynthetic precursor L-lysine to the medium stimulated swainsonine production approximately four-fold.