On January 15,Cell Discovery The journal published online the research group of zhouzhihua, Key Laboratory of synthetic biology, Institute of plant physiology and ecology, Center for excellence and innovation in molecular plant science, Chinese Academy of Sciences, entitledSynthesizing ginsenoside Rh2 in Saccharomyces cerevisiae cell factory at high-efficiency Research paper.
Ginsenosides are the main active ingredients in ginseng, a traditional precious medicinal material in China, and rareGinsenoside Rh2It has been widely reported that it can promote tumor apoptosis and inhibit tumor cell proliferation, invasion and metastasis, and help improve immunity. It is expected to become an auxiliary drug for cancer prevention and treatment. However, due to the extremely low content of ginsenoside Rh2 (less than 0.01% of the dry weight of ginseng roots), the current commercial ginsenoside Rh2 mainly extracts total saponins from ginseng plants, and further converts other protopanaxadiol saponins in the total saponins into ginsenoside Rh2 by chemical or biological deglycosylation. This method relies on the cultivation of ginseng plants (ginseng plants have a long cultivation cycle, are prone to pests, and have continuous cropping obstacles). The downstream separation process is complex, resulting in the high price of ginsenoside Rh2, which greatly limits its development and application. Moreover, obtaining trace ginsenoside Rh2 from ginseng resources will also cause waste of resources.
The application of synthetic biology technology has realized the de novo synthesis of a variety of rare active natural products by microbial fermentation. In the previous work (Wang et al Metab. Eng. 2015) the research group completed the functional identification of the key ugtpg45 element of the rare ginsenoside Rh2 synthesis pathway, and completely analyzed the synthesis pathway of rare ginsenoside Rh2. On this basis, the research group constructed the first generation Saccharomyces cerevisiae cell factory for de novo synthesis of Rh2 by monosaccharide fermentation. However, due to the low synthesis efficiency of protopanaxadiol (PPD) precursor and the poor adaptability of UGT components to the chassis, the synthesis efficiency of Rh2 is very low (16.9 mg / L).
In order to further improve the efficiency of Rh2 synthesis, aiming at the problems existing in the first generation cell factory, this study first redesigned and constructed the second generation PPD chassis cells, systematically enhanced the MVA pathway and optimized the expression of cytochrome P450,protopanaxadiolThe yield of 10L fermentor increased by more than 7.5 timesprotopanaxadiolThe yield reached 11.0g/l. Based on this new chassis, the study also made a further research onprotopanaxadiol. Finally, by integrating the above transformation strategies, the output of Rh2 was increased by more than 10 times, and the output of 10L fermentation tank reached 2.2g/l. This shows that compared with the traditional preparation process, the new process of de novo synthesis of Rh2 from glucose has obvious cost advantages.
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Progress in efficient synthesis of rare ginsenoside Rh2 by Saccharomyces cerevisiae cell factory