Influence of media and temperature on gliotoxin production in Aspergillus fumigatus strains.

Gliotoxin is a secondary metabolite of the epipolythiodioxopiperazine family with biologically active internal disulfide bridge. It is produced by many fungal species, including Aspergillus fumigatus and A. terreus. A. fumigatus, which produces gliotoxin and more than twenty other secondary metabolites, is the leading cause of invasive aspergillosis. Gliotoxin production in situ influence the development of aspergillosis. This study investigated the in vitro production of gliotoxin in nine A. fumigatus isolates from the upper respiratory tract of immunocompromised patients. The effects of media composition and incubation temperature were studied. Gliotoxin was extracted from biomass and its concentration was semi-quantitatively analysed using thin-layer chromatography. Gliotoxin production was higher in the yeast-extract liquid medium (YES) than in the synthetic Czapek-Dox liquid medium (CZA). Incubation at 37 degrees C resulted in higher gliotoxin production than at 25 degrees C, probably because higher temperatures favour expansive growth of the mycelium. Gliotoxin could be detected after three days of incubation at concentrations 4.06 mg mL(-1) (in YES at 37 degrees C) and 1.07 mg mL(-1) (in CZA at 25 degrees C). YES broth as a medium containing 4% sucrose and 2% of yeast extract is a very rich substrate for the production of gliotoxin in vitro.