Production of hesperetin from naringenin in an engineered Escherichia coli consortium

Hesperetin, a methoxylated flavanone, has numerous biological activities. Access to this compound is currently restricted by its low abundance in plants, which limits its practical applicability. To provide an alternative, eco-friendly production source, we developed a biosynthetic pathway of hesperetin in an engineered Escherichia coli consortium, which was fed with naringenin as a precursor and demonstrated good hesperetin production. The biosynthetic pathway was divided into two modules. The first recombinant host harbored the pathway genes from two different species: a flavonoid 3'-hydroxylase (F3'H) gene from Gentiana triflora and a cytochrome P450 reductase (CPR) gene from Arabidopsis thaliana. The second strain heterologously expressed a gene encoding a flavonoid 4'-O-methyltransferase (MpOMT) from Mentha × piperita, which was N-terminally fused to a Sumo tag. A construct expressing a 29 aa N-terminally truncated F3'H and CPR was the most effective combination for the conversion of naringenin. The strain expressing the Sumo-tagged MpOMT protein exhibited an increase in the final hesperetin titer, reaching 5.9 mg/L. Simultaneous overexpression of metK (coding for the endogenous S-adenosyl-l-methionine [SAM] synthase) further improved the hesperetin titer by 25.1%. Finally, the designed E. coli consortium harboring the two modules efficiently converted naringenin to hesperetin (37.1 mg/L). This work reports the construction of a multi-step in vivo cascade biocatalyst for the biotransformation of naringenin to hesperetin. It also illustrates the potential of the E. coli consortium system for producing other O-methylated flavonoids.