Abstract
Huperzine A (HupA) is a plant alkaloid that is of great interest as a therapeutic candidate for the treatment of Alzheimer's disease. However, the current production of HupA from plants in large quantity is unsustainable because the plant resource is scarce and the content of HupA in plants is extremely low. Surprisingly, this compound was recently found to be produced by various endophytic fungi, which are much more controllable than the plants due to simpler genetics and ease of manipulation. However, it might be due to the innate properties of endophytic symbiosis, that production of this chemical in large quantity from endophytes has not yet been put into practice. Endophytic Colletotrichum gloeosporioides ES026 was previously isolated from a HupA producing plant and the fungi also proved to produce HupA. In this study, various fermentation conditions were tried to optimize the production of HupA from C. gloeosporioides ES026. Optimization of these parameters resulted in a 25.58% increase in HupA yield. Potato extracts supplemented with glucose or sucrose but not maltose facilitated HupA producing from the fungi. A final concentration of 0.5-2% ethanol stimulated the growth of fungi while methanol with the same treatment slightly inhibited the growth. However, both methanol and ethanol greatly increased the HupA production with the highest yield of HupA (51.89% increment) coming from ethanol treatment. Further analysis showed that both ethanol and methanol were strong inducers of HupA production, while ethanol was partially used as a carbon source during fermentation. It was noticed that the color of that ethanol treated mycelia gradually became dark while methanol treated ones stayed grey during fermentation. The present study sheds light on the importance of optimizing the fermentation process, which, combined with effective inducers, maximizes production of chemicals of important economic interest from endophytic fungi.