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Combinatorial metabolic engineering of Saccharomyces cerevisiae for improved production of 7-dehydrocholesterol

Engineering Microbiology 2023年第4期3卷 29-37页

作者： Yuehao Gu Shuhui Chen Xue Jiao Qi Bian Lidan Ye Hongwei Yu Key Laboratory of Biomass Chemical Engineering(Education Ministry) College of Chemical and Biological EngineeringZhejiang UniversityHangzhou 310058China Institute of Bioengineering College of Chemical and Biological EngineeringZhejiang UniversityHangzhou 310058China

7-Dehydrocholesterol(7-DHC),a key pharmaceutical intermediate in the production of vitamin D3,has a wide range of applications.To explore fermentative synthesis of 7-DHC,a 7-DHC-producing Saccharomyces cerevisiae strain was constructed by blocking the competitive pathway,eliminating rate-limiting steps,altering global reg-ulation,and pathway compartmentalization.After blocking the competitive pathway by disrupting ERG5 and ERG6 and introducing DHCR24 from Gallus gallus,S.cerevisiae produced 139.72 mg/L(17.04 mg/g dry cell weight,hereafter abbreviated as DCW)7-DHC.Subsequent alteration of global regulation by deleting ROX1 and overexpressing UPC2-1 increased 7-DHC production to 217.68 mg/L(37.56 mg/g DCW).To remove the accu-mulated squalene,the post-squalene pathway was strengthened by co-overexpression of PGAL1-driven ERG11 and PGAL10-driven ERG1,which improved 7-DHC titer and yield to 281.73 mg/L and 46.78 mg/g DCW,respectively,and reduced squalene content by 90.12%.We surmised that the sterol precursors in the plasma membrane and peroxisomes may not be accessible to the pathway enzymes,thus we re-localized DHCR24p and Erg2p-GGGGS-Erg3p to the plasma membrane and peroxisomes,boosting 7-DHC production to 357.53 mg/L(63.12 mg/g DCW).Iron supplementation further increased 7-DHC production to 370.68 mg/L in shake flasks and 1.56 g/L in fed-batch fermentation.This study demonstrates the power of global regulation and subcellular relocalization of key enzymes to improve 7-DHC synthesis in yeast.

关键词： 7-Dehydrocholesterol Saccharomyces cerevisiae Metabolic engineering global regulation Pathway re-localization

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Paradox of international maritime organization's carbon intensity indicator

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Communications in Transportation Research 2021年第1期1卷 26-30页

作者： Shuaian Wang Harilaos N.Psaraftis Jingwen Qi Department of Logistics and Maritime Studies The Hong Kong Polytechnic UniversityHong Kong Special Administrative Region Department of Technology Management and EconomicsTechnical University of DenmarkDenmark

The 76th session of the Marine Environment Committee(MEPC 76)of the International Maritime Organization adopted several mandatory measures in June 2021 to reduce carbon emissions from ships.One of the measures is the carbon intensity indicator(CII),which is the carbon emissions per unit transport work for each ship.Several options of CIIs are available and none of them is chosen to be applied yet.We prove that,at least in theory,requiring the attained annual CII of a ship to be less than a reference value,no matter which CII option is applied,may increase its carbon emissions.Therefore,more elaborate models,combined with real data,should be developed to analyze the effectiveness of each CII option and possibly to design a new CII.

关键词： Maritime transportation Carbon dioxide emission International maritime organization(IMO) global regulation

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