Efficient Production of δ-Guaiene, an Aroma Sesquiterpene Compound Accumulated in Agarwood, by Mevalonate Pathway-Engineered Escherichia coli Cells

Mevalonate pathway for isoprenoid biosynthesis was constructed in Escherichia coli cells by the transformation with a gene cluster isolated from Streptomyces sp., and farnesyl diphosphate synthase and δ-guaiene synthase genes were coexpressed in this strain. This transformant was capable of liberating an appreciable amount of δ-guaiene, an aroma sesquiterpene compound accumulated in agarwood, and its concentration was elevated to more than 30 μg/ml culture by the incubation with mevalonolactone as an isoprene precursor in a nutrient-enriched Terrific broth. Coexpression of type 1 isopentenyl diphosphate isomerase plus acetoacetyl-CoA ligase genes also enhanced δ-guaiene production, and the concentration of the compound was approximately 38 - 42 μg/ml culture in the presence of mevalonolactone or lithium acetoacetate. These results clearly indicate that mevalonate pathway-engineered E. coli cells showed an appreciable δ-guaiene producing activity in the en- riched medium in the presence of appropriate isoprene precursors.

Enzymatic synthesis of myricetin 3-O-galactoside through a whole-cell biocatalyst

Objective:Myricetin 3-O-galactoside is an active compound with pharmaceutical potential.The insufficient supply of this compound becomes a bottleneck in the druggability study of myricetin 3-Ogalactoside.Thus,it is necessary to develop a biosynthetic process for myricetin 3-O-galactoside through metabolic engineering.Methods:Two genes OcSUS1 and OcUGE1 encoding sucrose synthase and UDP-glucose 4-epimerase were introduced into BL21(DE3)to reconstruct a UDP-D-galactose(UDP-Gal)biosynthetic pathway in Escherichia coli.The resultant chassis strain was able to produce UDP-Gal.Subsequently,a flavonol 3-O-galactosyltransferase DkFGT gene was transformed into the chassis strain producing UDP-Gal.An artificial pathway for myricetin 3-O-galactoside biosynthesis was thus constructed in E.coli.Results:The obtained engineered strain was demonstrated to be capable of producing myricetin 3-Ogalactoside,reaching 29.7 mg/L.Conclusion:Biosynthesis of myricetin 3-O-galactoside through engineered E.coli could be achieved.This result lays the foundation for the large-scale preparation of myricetin 3-O-galactoside.