Strain Engineering and Fermentation Process Development toward Supplying Semi-Synthetic Artemisinin. A Key Component of Antimalarial Combination Therapies

Malaria threatens 350-500 million lives every year, with over 1 million deaths, primarily children under the age of five. Artemisinin based Combination Therapies (ACT's) are recommended by World Health Organization for the treatment of uncomplicated malaria. Although currently more costly than traditional drug treatments, ACT's are preferred since P. falciparum resistance has been observed relative to almost all currently used antimalarials except for artemisinin and its deriviatives. Currently the only source of artemisinin is extraction from the plant Artemisia annua. Consequently, the supply of artemisinin for ACT's can be variable, due to a long planting cycles and climate-dependent yields. By cloning the genes from the A. annua artemisinin biosynthetic pathway into Escherichia coli and Saccharomyces cerevisiae, we have developed a process to produce semi-synthetic artemisinin through fermentation and chemical conversion. The biosynthetic pathways were constructed for two artemisinin precursors, amorpha-4,11-diene and artemisinic acid. Strain and process improvements increased production of amorpha-4,11-diene in E. coli to 25 g/L in small scale bioreactors. Artemisinic acid processes at the lab scale were developed for both organisms with titers > 1 g/L.This alternative artemisinin production option, if commercial scale production can be achieved, may be a good way to supplement the plant-derived supply since fermentation processes have a shorter cycle time, can be scaled to meet demand, and result in consistent quality.