Design of a fungal biofilm reactor for the production of Astin, an anticancerous secondary metabolite

Abstract

Plants and endophyte micro-organisms have been used for thousands of years to produce compounds for medicinal purposes. In this work, the optimization of the production of an anticancerous molecule, astin C, by Cyanodermella asteris, an endophyte fungus to the plant Aster tatricus, was studied. Firstly, a detection technique of astin was developed, by combining analysis with HPLC-UV and UPLC-MS. Then, in flasks, two types of fungal growth were studied, planktonic and in a biofilm, as well as the medium concentration and the culture time. The comparison was done on the astin yield mainly, but also on the biomass one. It appears that the planktonic growth had a higher biomass yield while the biofilm growth has a higher astin yield. Furthermore, the higher the medium concentration and the culture time were, the higher the astin and biomass production were. With a pH value of 4, there was no growth while for a value of 5, the growth is smaller than the one observed without a set pH. Medium replacement after a certain amount of time was also tested, but led to a high standard deviation and thus to inconclusive results. Secondly, the reactor experiments allowed to highlight the importance of aeration for the growth and to confirm the capacity of the fungus to produce astin during a biofilm growth on a stainless steel support, but with a lower yield than during a flasks culture. Thirdly, the consumption rate of the main elements of the culture medium was determined.