Carbon distribution and redirection of metabolism in Paecilomyces fumosoroseus during solid-state and liquid fermentations

Dipicolinic acid (DPA) and oxalic acid (OXA) are insecticidal metabolites produced by the entomopathogenic fungus Paecilomyces fumosoroseus. A chemically defined medium was used to investigate the influence of the culture system on the carbon distribution in the fermentation products and the adaptative response to zinc limitation. In solid-state fermentation, carbon was mainly employed for biomass production, while in submerged fermentation, it was significantly directed to synthesis of DPA, OXA and other compounds, especially under zinc limitation. In solid-state fermentation, OXA and DPA were growth-associated products, while in submerged fermentation at low zinc levels, OXA and DPA were partially-growth-associated, perhaps because the metabolism was redirected when zinc became limiting. Entomopathogenic fungal action can be enhanced by the use of insecticidal metabolites, since our results show that biomass and metabolites production vary according to the culture system, this fact should be considered to choose the most appropriate spore production system.