Fig. 6.

Construction of the combined pathway and its use for hydroxytyrosol biosynthesis. a The designed combined pathway. The dashed arrows indicate the steps lacking in highly efficient enzymes; b OD₄₀₀ of the periodate assay of HpaBC mutants selected after two rounds of positive screening with tyrosol and tyramine as substrates individually; WT, wild-type; c Time courses of product and intermediate production of the combined pathway; d Hydroxytyrosol productions under different substrate-feeding strategies. Feeding method A: fed with 15 mM tyrosine when inoculation; Feeding method B: fed with 7.5 mM tyrosine at 0 and 12 h after inoculation; Feeding method C: fed with 5 mM tyrosine at 0, 12, and 24 h after inoculation. The data are shown in b, c and d are from three replicate experiments and are expressed as the mean ± SD. Source data of b–d are provided in the Excel format Source Data file