Factors Influencing Production of Fusaristatin A in Fusarium graminearum.

Fusarium graminearum is a ubiquitous plant pathogen, which is able to produce several bioactive secondary metabolites. Recently, the cyclic lipopeptide fusaristatin A was isolated from this species and the biosynthetic gene cluster identified. Fusaristatin A consists of a C24 reduced polyketide and the three amino acids dehydroalanine, β-aminoisobutyric acid and glutamine and is biosynthesized by a collaboration of a polyketide synthase and a nonribosomal peptide synthetase. To gain insight into the environmental factors, which controls the production of fusaristatin A, we cultivated F. graminearum under various conditions. We developed an LC-MS/MS method to quantify fusaristatin A in F. graminearum extracts. The results showed that yeast extract sucrose (YES) medium was the best medium for fusaristatin A production and that the optimal pH was 7.5 and temperature 25-30 °C. Furthermore, production of fusaristatin A was more than four times higher in stationary cultures than in agitated cultures when F. graminearum was grown in liquid YES medium. The results also showed that fusaristatin A was only present in the mycelium and not in the liquid, which suggests that fusaristatin A is stored intracellulally and not exported to the extracellular environment.