Engineering metazoan fatty acid synthase to control chain length applied in yeast.

Metazoan fatty acid (FA) synthases (mFASs) facilitate the de novo synthesis of C16- and C18-FAs through iterative extensions within the FA cycle and hydrolytic release. Here we re-engineer mFAS to fine-tune the interplay between FA extension and FA hydrolytic release for the targeted production of short- and medium-chain fatty acids. Single amino acid exchanges in the ketosynthase domain can redirect FA product profiles from predominantly C8 (G113W) to C8/C10 (G113F) and C12/C14 (G113M). Integration of a thioreductase domain enables the production of medium-chain fatty aldehydes and alcohols. We apply our approach for controlling chain length in FA biosynthesis to the microbial production of C10- and C12-FAs, translate it into a yeast cell factory and achieve C10/C12-FAs titers of 674 mg l−1 and 67% purity of total free FAs. Our work demonstrates a modular platform for programmable FA synthesis and paves the way toward sustainable bioproduction of valuable oleochemicals. The authors report on engineering metazoan fatty acid synthase variants with tunable selectivity to obtain short- and medium-chain fatty acids, alcohols and aldehydes. Pairing these optimized enzymes with a yeast strain designed for efficient β-oxidation yields high production levels of medium-chain fatty acids.