Fig. 1

Functional identification of two key enzymes of F3H and FLS in kaempferol biosynthetic pathway. a The biosynthetic pathway from naringenin to kaempferol. Naringenin is converted into dihydrokaempferol with flavanone 3β-hydroxylase (F3H), and dihydrokaempferol is converted into kaempferol via flavonol synthase (FLS). b HPLC analysis of the product in whole cell catalysis with overexpression of F3H and FLS in yeast. Chromatogram data were collected at 335 nm. Peak 1, (+)-dihydrokaempferol; peak 2, kaempferol; peak 3, (2S)-naringenin. (2S)-naringenin was the substrate and was detected in the wild type W3-Y22. c LC–MS analysis of dihydrokaempferol produced by W3-AtF3H in whole cell catalysis. d LC–MS analysis of kaempferol produced by W3-MdFLS in whole cell catalysis. e Production of kaempferol and dihydrokaempferol of recombinant yeast strain expressing FLS from five plant species. Recombinant yeast strain expressing AtF3H and FLS from different species were fermented. Data are shown as average in triplicate assays. Error bar shows standard division. Different superscript letter indicates significant difference in Tukey analysis (α = 0.05)