De novo biosynthesis of myricetin， kaempferol and quercetin in Streptomyces albus and Streptomyces coelicolor.

Flavonols are a flavonoid subfamily widely distributed in plants， including several ones of great importance in human and animal diet (apple， tomato， broccoli， onion， beans， tea). These polyphenolic nutraceuticals exert potent antimicrobial (membrane potential disruptors)， antioxidant (free-radical scavengers)， pharmacokinetic (CYP450 modulators)， anti-inflammatory (lipoxygenase inhibitors)， antiangiogenic (VEGF inhibitors) and antitumor (cyclin inhibitors) activities. Biotechnological production of these nutraceuticals， for example via heterologous biosynthesis in industrial actinomycetes， is favored since in plants these polyphenols appear as inactive glycosylated derivatives， in low concentrations or as part of complex mixtures with other polyphenolic compounds. In this work， we describe the de novo biosynthesis of three important flavonols， myricetin， kaempferol and quercetin， in the industrially relevant actinomycetes Streptomyces coelicolor and S. albus. De novo biosynthesis of kaempferol， myricetin and quercetin in actinomycetes has not been described before.