Construction Of The Dammarenediol-Ⅱ Biosynthetic Module And The Adaption Between The Module And Saccharomyces Cerevisiae

The roots of Panax ginseng is valued for its ginsenosides that has strongpharmacological properties of protecting cardiovascular and liver, antineoplastic,antifatigue, immuno-modulatory and anti-ageing. Panax ginseng roots have been rareChinese herbal medicine for thousands of years. The production of ginsenosides isnow mainly dependent on plant cultivating, plant tissue and cell culturing,bioconversion. Studies of these production modes have achieved great progresses, butthe productivity is far away from the market demand. Over the years, the successes ofsynthetic biology in microbial production of plant terpenoids provide reliablereferences for ginsenosides producing in microbes.Saccharomyces cerevisiae has been an outstanding cell factory for its safety andsimple culturing, clear genetic background and mature genetic manipulation, andlimited secondary metabolism. Natural isoprenoid pathway in Saccharomycescerevisiae provides precursors for terpenoids, as it is Saccharomyces cerevisiae whichwill act as the best chassis cell to construct new pathways of heterogenous planttrepenoids.In this paper, we construct a primary engineered Saccharomyces cerevisiaetransformed with dammarenediol-II synthase (encoded by DS gene) modules.Targeting on enhancing the accumulation of2,3-oxidosqualene as a precursor,rate-limiting genes of Hmg1(encoding HMG-CoA reductase), Erg20(encodingfarnesyl pyrophosphate synthase) and Erg1(encoding squalene epoxidase) wereoverexpressed, and Erg27expression was weakened to establish an effective platformin Saccharomyces cerevisiae for triterpenoids synthesis.The introduction of modules to chassis cell will make great impact on it, evensuppress its growth, and make the biosynthetic pathway do not work. So, furtheradaptions between modules and chassis cell were tried to make higherdammarenediol-II production. Codon optimization of DS for Saccharomycescerevisiae was performed to improve its transcriptional level; A module of Erg1fromCandida albicans was established to regulate squalene epoxidase expression atprotein level; Fusion proteins of dammarenediol-II synthase and squalene epoxidase were work out to maximum the transformation of2,3-oxidosqualene todammarenediol-II.The isoprenoid pathway in saccharomyces cerevisiae produces many keymetabolites for its growth, complex but precise regulation is demanded to balance itsneeds.so the transformation of this pathway will be comparatively hard. Here weestablished a platform in saccharomyces cerevisiae for triterpenoids production; theconstruction of dammarenediol-II producing saccharomyces cerevisiae and theadaption between modulers and chassis cell provide foundation for the developmentof dammarenediol-II high-producing saccharomyces cerevisiae.