Isosorbide dinitrate bioconversion by Beauveria strains: implication of glutathione transferase levels

Summary The level of glutathione S-transferase (GSH0ST) activity was determined in growing cultures and in washed resting cells of Beauveria strains with and without addition of isosorbide dinitrate (ISDN), by following the reaction with o-dinitrobenzene (o-DNB). The level of GSH-ST varied according to the pH changes of the medium and decreased during culture. The enzymatic activity measured with o-DNB did not correlate with ISDN bioconversion carried out either with B. sulfurescens or B. tenella. Immediately after starting incubation of the resting cells with ISDN, the level of GSH-ST activity initially increased, but declined afterwards, whereas the bioconversion process continued and reached 500 mg/l isosorbide 5-mononitrate. When 1-chloro-2,4-dinitrobenzene was used as a substrate for the evaluation of GSH-ST activity using B. tenella, a conjugation product having a UV absorption at 410 nm was formed.