Efficient production of cembratriene-ol in Escherichia coli via systematic optimization

Screening of ent-copalyl diphosphate synthase and metabolic engineering to achieve de novo biosynthesis of ent-copalol in Saccharomyces cerevisiae

The diterpene ent-copalol is an important precursor to the synthesis of andrographolide and is found only in green chiretta (Andrographis paniculata). De novo biosynthesis of ent-copalol has not been reported, because the catalytic activity of ent-copalyl diphosphate synthase (CPS) is very low in microorganisms. In order to achieve the biosynthesis of ent-copalol, Saccharomyces cerevisiae was selected as the chassis strain, because its endogenous mevalonate pathway and dephosphorylases could provide natural promotion for the synthesis of ent-copalol. The strain capable of synthesizing diterpene geranylgeranyl pyrophosphate was constructed by strengthening the mevalonate pathway genes and weakening the competing pathway. Five full-length ApCPSs were screened by transcriptome sequencing of A. paniculata and ApCPS2 had the best activity and produced ent-CPP exclusively. The peak area of ent-copalol was increased after the ApCPS2 saturation mutation and its configuration was determined by NMR and ESI-MS detection. By appropriately optimizing acetyl-CoA supply and fusion-expressing key enzymes, 35.6 mg/L ent-copalol was generated. In this study, de novo biosynthesis and identification of ent-copalol were achieved and the highest titer ever reported. It provides a platform strain for the further pathway analysis of andrographolide and derivatives and provides a reference for the synthesis of other pharmaceutical intermediates.

Biosynthetic pathway redesign in non-conventional yeast for enhanced production of cembratriene-ol

Cembratriene-ol (CBT-ol), a plant-derived macrocyclic diterpene with notable insecticidal activity, has attracted considerable attention with respect to the development of sustainable and green biopesticides. Currently, CBT-ol production is limited by an inefficient and costly plant extraction strategy. Herein, CBT-ol production was enhanced by redesigning the CBT-ol biosynthetic pathway in Candida tropicalis, with subsequent truncation of CBT-ol synthase further increasing CBT-ol production. Moreover, bottlenecks in the CBT-ol biosynthetic pathway were eliminated by adjusting the gene dosage of the rate-limiting enzymes. Ultimately, the resulting strain C. tropicalis CPPt-03D produced 129.17 mg/L CBT-ol in shaking flasks (a 144-fold increase relative to that of the initial strain C01-CD) with CBT-ol production reaching 1,425.76 mg/L in a 5-L bioreactor, representing the highest CBT-ol titer reported to date. These findings provide a green process and promising platform for the industrial production of CBT-ol and lays the foundation for organic farming.

Boosting production of cembratriene-ol in Saccharomyces cerevisiae via systematic optimization

Cembratriene-ol is a good biodegradable biopesticide ingredient with future potential applications in the field of sustainable agriculture. Cembratriene-ol is a monocyclic diterpenoid compound that is synthesized only in the trichome gland of Nicotiana plants. In this study, geranylgeranyl diphosphate synthase gene ggpps from Taxus canadensis and cbts*Δp were heterologously expressed in Saccharomyces cerevisiae W303-1A to successfully synthesize cembratriene-ol. The titer of cembratriene-ol was increased by 1.84-fold compared to the control by overexpressing the S. cerevisiae bifunctional (2E,6E)-farnesyl diphosphate synthase genes ERG20 and cbts*Δp under one promoter PGAP . The titer of cembratriene-ol in the engineered S. cerevisiae BY4741 was increased by 1.39-fold compared to the engineered S. cerevisiae W303-1A. The titer of cembratriene-ol in the engineered S. cerevisiae BY4741 was increased by 2.22-fold compared to the control by overexpressing ERG20 and cbts*Δp, respectively, using two promoters PGAP . Cembratriene-ol was found to be successfully synthesized via the integrated expression of cbts*Δp, ggpps and ERG20 on the genome of S. cerevisiae BY4741. The titer of cembratriene-ol in S. cerevisiae S25 was further increased by 1.80-fold compared to the control via dynamic control of the squalene synthase gene ERG9. Overexpression of the genes cbts*Δp and ggpps using pY26-GPD-TEF in S. cerevisiae S25 with their integration expression increased the titer of cembratriene-ol by 26.1-fold compared to S. cerevisiae S25. The titer of cembratriene-ol was significantly enhanced by mitochondrial compartmentalized expression of cbts*Δp and ggpps, which was 76.3-fold higher than that of the initial strain constructed. It was indicated that the systematic optimization has great potential in facilitating high-level production of cembratriene-ol production in S. cerevisiae.