Improved Production of Arachidonic Acid by Combined Pathway Engineering and Synthetic Enzyme Fusion in Yarrowia lipolytica

Arachidonic acid (ARA, C20:4) is a typical ω-6 polyunsaturated fatty acid with special functions. Using Yarrowia lipolytica as an unconventional chassis, we previously showed the performance of the Î"-6 pathway in ARA production. However, a significant increase in the Î"-9 pathway has rarely been reported. Herein, the Î"-9 pathway from Isochrysis galbana was constructed via pathway engineering, allowing us to synthesize ARA at 91.5 mg L^-1. To further improve the ARA titer, novel enzyme fusions of Î"-9 elongase and Î"-8 desaturase were redesigned in special combinations containing different linkers. Finally, with the integrated pathway engineering and synthetic enzyme fusion, a 29% increase in the ARA titer, up to 118.1 mg/L, was achieved using the reconstructed strain RH-4 that harbors the rigid linker (GGGGS). The results show that the combined pathway and protein engineering can significantly facilitate applications of Y. lipolytica.