Astin C production by the endophytic fungus Cyanodermella asteris in planktonic and immobilized culture conditions

The fungal endophyte Cyanodermella asteris was recently isolated from the medicinal plant Aster tataricus. This fungus produces astin C, a cyclic pentapeptide with anticancer and anti-inflammatory properties. The production of this secondary metabolite was compared in immobilized and planktonic conditions. For immobilized cultures, a stainless steel packing immersed in the culture broth was used as a support. In these conditions, the fungus exclusively grew on the packing, which provides a considerable advantage for astin C recovery and purification. C. asteris metabolism was different according to the culture conditions in terms of substrate consumption rate, cell-growth, and astin C production. Immobilized-cell cultures yielded a 30% increase of astin C production associate to a 39% increase in biomass. The inoculum type as spores rather than hyphae, and a pre-inoculation washing procedure with sodium hydroxide, turned out to be beneficial both for astin C production and fungus development onto the support. Finally, influence of culture parameters such as pH and medium composition, on astin C production was evaluated. With optimized culture conditions, astin C yield was further improved reaching a five times higher final specific yield compared to the value reported with astin C extraction from Aster tataricus (0.89 and 0.16 mg/g respectively).