Optimization of the precursor supply for an enhanced FK506 production in .

Tacrolimus (FK506) is a macrolide widely used as immunosuppressant to prevent transplant rejection. Synthetic production of FK506 is not efficient and costly, whereas the biosynthesis of FK506 is complex and the level produced by the wild type strain, , is very low. We therefore engineered FK506 biosynthesis and the supply of the precursor L-lysine to generate strains with improved FK506 yield.