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.