Abstract
Ginseng (Panax ginseng) and its bioactive components, ginsenosides, are popular medicinal herbal products, exhibiting various pharmacological effects. Despite their advocated use for medication, the long cultivation periods of ginseng roots and their low ginsenoside content prevent mass production of this compound. Yeast Saccharomyces cerevisiae was engineered for production of protopanaxadiol (PPD), a type of aglycone characterizing ginsenoside. PPD-producing yeast cell factory was further engineered by obtaining a balance between enzyme expressions and altering cofactor availability. Different combinations of promoters (PGPD, PCCW12, and PADH2) were utilized to construct the PPD biosynthetic pathway. Rerouting the redox metabolism to improve NADPH availability in the engineered S. cerevisiae also increased PPD production. Combining these approaches resulted in more than an 11-fold increase in PPD titer over the initially constructed strain. The series of metabolic engineering strategies of this study provides a feasible approach for the microbial production of PPD and development of microbial platforms producing other industrially-relevant terpenoids.
Highlights
Ginseng (Panax ginseng) is one of the most widely used medicinal herbs in Asia, Europe, and North America to alleviate fatigue, enhance immunity, and improve physical performance
We show that a series of metabolic engineering strategies that alter cofactor availability and redirect metabolic flux toward the synthetic ginsenoside pathway results in increased PPD production in S. cerevisiae
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Summary
Ginseng (Panax ginseng) is one of the most widely used medicinal herbs in Asia, Europe, and North America to alleviate fatigue, enhance immunity, and improve physical performance. Cultivation of ginseng requires extensive effort, since its growth is reliant upon optimizing many environmental factors, such as soil, shade, climate, pathogens, and pests[7]. Microorganisms, such as Escherichia coli and Saccharomyces cerevisiae, provide alternative and attractive ways of producing diverse natural chemicals from renewable resources. The synthetic pathway for ginsenoside production in S. cerevisiae encompasses many of the challenges associated with engineering metabolic pathways to improve production titers, through enhancing the activity of related enzymes and increasing availability of precursors and relevant cofactors, while preventing severe growth inhibition. Further optimization through the application of metabolic engineering strategies and synthetic biology tools is required to enable mass production of ginsenosides at a reduced price and broader application for clinical trials and the food supplement industry
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