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Team of professor Li Chun publishes research result of “Fabrication of α-amyrin with productive engineered saccharomyces cerevisiae” on Synthetic Biology top journal

release date :2018-11-18 08:36:00  |   [ close window ]ViewCount:

    Translator:  News Agency of BIT, Bai Lige

    Editor:  News Agency of BIT

  Terpenoid is the largest family among secondary metabolites of plants, widely distributed in nature. α-Amyrin is a plant-derived pentacyclic triterpenoid, with a lot of important physiological and pharmacological activities. The formation of α-amyrin from (3S)-2,3-oxidosqualene is catalyzed by α-amyrin synthase (α-AS), a member of the oxidosqualene cyclase (OSC) protein family. Since the content of the α-amyrin is extremely low in the plants, separation and purification steps are complicated, commercial development and production are not yet available. The engineered saccharomyces cerevisiae with efficient α-amyrin production pathway could be used as a sustainable solution to produce α-amyrin.

  In order to improve the production of α-amyrin in saccharomyces cerevisiae, researchers characterized two kinds of α– AS, EjAS and MdOSC1 from loquat and apple through rigorous screening and phylogenetic analysis of biological information. The specific activity of the purified EjAS and MdOSC1 were 0.0032 and 0.0293μmol/ min/ mg. EjAS produced α-amyrin and beta perfume resin at 17:3 rate, MdOSC1 produced alpha perfume resin, β-amyrin and lupeol at 86:13:1 rate. The results showed that MdOSC1 has higher specific activity and α-amyrin production rate.

Figure1. The biosynthesis of triterpene

  Before putting MdOSC1 into saccharomyces cerevisiae, researches carried out metabolic engineering transformation of Saccharomyces cerevisiae. α-amyrin’s synthetic precursor (3S) -2,3- oxidation of squalene came from MVA process, overexpression of four key enzymes in the MVA pathway (squalene monooxygenase ERG1, HMG synthase tHMG1, FPP synthase ERG20 and squalene synthase ERG9) increased the supply of (3S) -2,3-oxidized squalene to increase the yield of terpenoids. However, Lanosterol synthase ERG7 from Saccharomyces cerevisiae can catalyze the synthesis of lanosterol and ergosterol using (3S) -2,3-oxidized squalene as substrate, which is the main competitive way to synthetize amyrin. In order to further improve the production of α-amyrin, researches inhibited ERG7 expression by using CRISPR/dCas9 system, the metabolic flow of (3S) -2,3-oxidized squalene to lanosterol was reduced, and the synthetic pathway of α-amyrin was increased.

  According to the research, by introducing α-amyrin synthase MdOSC1 into saccharomyces cerevisiae and increasing the supply of (3S) -2,3-squalene oxide, the researchers were able to produce alpha-aromatic resin alcohol efficiently. The shaking flask yield reached 11.97 (+0.61mg/L), 5.8 times the highest reported yield. This research was published on ACS synthetic biology 2018, 7(10), 2391-2402. The first author of the article is Yu Yuan, doctoral student of School of Chemical Engineering, Tianjin University, under the guidance of professor Li Chun and professor Huo Yixin, co-correspondent author of the article of School of Life Science of BIT.

Figure2. The synthetic pathway of α-amyrin in saccharomyces cerevisiae

  Since its establishment in 2005, iBT-SynBios has focused on stress-resistant biocatalysis and synthetic biology. It has published more than 120 articles in top journals in the field of bioengineering and chemical engineering such as Metab Eng, ACS Synth Biol, Nature Comm, Curr Opin Biotech, AIChE J, J Phys Chem Lett, J Biol Chem, Chem Eng Sci, Chem Eng J, C Nu. Leic Acids Res, Ind Eng Chem Res and Bioresource Technol. They were granted 26 invention patents and 5 provincial and ministerial science and technology awards. The research group focuses on using synthetic biotechnology and enzymatic catalysis technology to innovate traditional microbial fermentation and biotransformation modes. They will continue to carry out research on the construction of natural product synthesis pathways, optimization of pathways, precise regulation and integration of biological processes and provide new ideas and new methods for the realization of green and efficient bio-manufacturing of drugs and bio-based chemicals.

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