Ginsenosides, the major bioactive components of Panax ginseng, are regarded as promising high-value pharmaceutical compounds. In ginseng, ginsenosides are produced from their precursor protopanaxadiol. Recently, an artificial biosynthetic pathway of protopanaxadiol was built in Saccharomyces cerevisiae by introducing a P. ginseng dammarenediol-II synthase, a P. ginseng cytochrome P450-type protopanaxadiol synthase (PPDS), and a Arabidopsis thaliana NADPH-cytochrome P450 reductase (ATR1). In this engineered yeast strain, however, the low metabolic flux through PPDS resulted in a low productivity of protopanaxadiol. Moreover, health of the yeast cells was significantly affected by reactive oxygen species released by the pool coupling between PPDS and ATR1. To overcome the obstacles in protopanaxadiol production, PPDS was modified through transmembrane domain truncation and self-sufficient PPDS-ATR1 fusion construction in this study. The fusion enzymes conferred approximately 4.5-fold increase in catalytic activity, and 71.1% increase in protopanaxadiol production compared with PPDS and ATR1 co-expression. Our in vivo experiment indicated that the engineered yeast carrying fusion protein effectively converted 96.8% of dammarenediol-II into protopanaxadiol. Protopanaxadiol production in a 5 L bioreactor in fed-batch fermentation reached 1436.6 mg/L. Our study not only improved protopanaxadiol production in yeast, but also provided a generic method to improve activities of plant cytochrome P450 monooxygenases. This method is promising to be applied to other P450 systems in yeast. Biotechnol. Bioeng. 2016;113: 1787-1795. © 2016 Wiley Periodicals, Inc.

Ethanol is a more reduced substrate than sugars. Here, 13C‐metabolic flux analysis (MFA) revealed that ethanol catabolism could supply sufficient acetyl‐CoA and reducing equivalent for PPD biosynthesis. Then, we described modular engineering strategy to optimize a multigene pathway for protopanaxadiol (PPD) production from ethanol in Saccharomyces cerevisiae. PPD biosynthesis was divided into four modules: mevalonate (MVA) pathway module, triterpene biosynthesis module, sterol biosynthesis module, and acetyl‐CoA formation module. Combinatorially overexpressing every gene in MVA pathway and optimizing metabolic balance in triterpene biosynthesis module led to significantly enhanced PPD production (42.34 mg/L/OD600). In sterol biosynthesis module, fine‐tuning lanosterol synthase gene (ERG7) expression using TetR–TetO gene regulation system enabled further production improvement (51.26 mg/L/OD600). Furthermore, increasing cytoplasmic acetyl‐CoA supply by overexpressing a Salmonella ACS (acetyl‐CoA synthetase gene) mutant ACSseL641P improved PPD production to 66.55 mg/L/OD600. In 5 L bioreactor, PPD production of the best‐performing strain WLT‐MVA5 reached 8.09 g/L, which has been the highest titer of plant triterpene produced in yeast. © 2018 American Institute of Chemical Engineers AIChE J, 65: 866–874, 2019

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Ursolic acid and oleanolic acid are pentacyclic triterpenoid compounds with a variety of biological activities. A mixture of ursolic acid and oleanolic acid has higher antitumor activity than the individual acids. We have developed a simultaneous biosynthesis pathway for different proportions of ursolic acid and oleanolic acid in Saccharomyces cerevisiae. The ScLCZ08 strain produced 175.15 mg/L of the ursolic acid precursor α‐amyrin, the highest amount reported. Ursolic and oleanolic acid titers and proportions were optimized using Medicago truncatula amyrin C‐28 oxidase and Arabidopsis thaliana cytochrome P450 reductase. Using glucose and ethanol fed‐batch fermentation strategies, the final ursolic acid and oleanolic acid titers were 123.27 and 155.58 mg/L, respectively, demonstrating 4.77‐fold and 4.95‐fold higher production than the parent strain. The ScLCZ11 strain displayed the highest ursolic acid production obtained via microbial fermentation in fed‐batch culture to date. © 2018 American Institute of Chemical Engineers AIChE J, 64: 3794–3802, 2018

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Shengli Oilfield, located in Northeast China, is one of the largest and oldest oilfields in China. The field production peaked in 1991 and the overall water cut has reached 95 % in 2012. The decline in production and the increasing demand for fossil energy have motivated the Shengli Oilfield Company (SLOF) to seek feasible enhanced oil recovery methods. Since 1992, more than 60 units at Shengli field have received injection of polymer or a combination of polymer and low-concentration surfactants. Partially hydrolyzed polyacrylamide and petroleum sulfonate were chosen for most polymer flood projects. Field cases demonstrated that polymer flood and surfactant-polymer flood could effectively increase oil rate, decrease water cut and improve oil recovery. This paper reviews several unique field trials at Shengli Oilfield. The earlier polymer flood projects targeted relatively ideal reservoirs with low temperature and low water salinity. However the undergoing polymer flood projects and future projects have to face very challenging reservoir conditions. Loss of polymer viscosity and reservoir heterogeneity affect the success of polymer flood projects. Future research at SLOF will focus on developing more tolerant polymers and improving the flow of polymer in reservoirs.