Systematic optimization of the yeast cell factory for sustainable and high efficiency production of bioactive...

Ginsenoside Compound K (CK) has been recognized as a major functional component that is absorbed into the systemic circulation after oral administration of ginseng. CK demonstrates diverse bioactivities. A phase I clinical study indicated that CK was a potential candidate for arthritis therapy. However, a phase II clinical study was suspended because of the high cost associated with the present CK manufacturing approach, which is based on the traditional planting-extracting-biotransforming process. We previously elucidated the complete CK biosynthetic pathway and realized for the first time de novo biosynthesis of CK from glucose by engineered yeast. However, CK production was not sufficient for industrial application. Here, we systematically engineered Saccharomyces cerevisiae to achieve high titer production of CK from glucose using a previously constructed protopanaxadiol (PPD)-producing chassis, optimizing UGTPg1 expression, improving UDP-glucose biosynthesis, and tuning down UDP-glucose consumption. Our final engineered yeast strain produced CK with a titer of 5.74 g/L in fed-batch fermentation, which represents the highest CK production in microbes reported to date. Once scaled-up, this high titer de novo microbial biosynthesis platform will enable a robust and stable supply of CK, thus facilitating study and medical application of CK.