Metabolic engineering of Escherichia coli with electron channelling for the production of natural products

The biosynthesis of natural products often requires eukaryotic cytochrome P450s (P450s) in combination with P450 reductase, in physical proximity, to perform electron-transfer reactions. Unfortunately, functional expression of eukaryotic P450s in bacteria remains generally difficult. Here we report an electron channelling strategy based on the application of Photorhabdus luminescens CipB scaffold protein, which allows efficient electron transfer between P450s and reductases by bringing these enzymes in close proximity. The general applicability of this electron channelling strategy is proved by developing recombinant Escherichia coli strains producing lutein, (+)-nootkatone, apigenin and l-3,4-dihydroxyphenylalanine (l-DOPA), each of which requires P450s in its biosynthetic pathway. The production titres are then further enhanced by increasing the haem pathway flux or by optimization of the culture conditions. Remarkably, the final lutein strain produced 218.0 mg l−1 of lutein with a productivity of 5.01 mg l−1 h−1 in fed-batch fermentation under optimized culture conditions.