Metabolic Engineering of Yarrowia lipolytica for Efficient De Novo Synthesis of Astaxanthin Glucosides via Enhanced UDP-Glucose Supply
Astaxanthin is a high-value carotenoid used in nutrition, cosmetics, pharmaceuticals, and biotechnology, but its poor water dispersibility and oxidative stability limit its formulation. Here, we engineered yeast Yarrowia lipolytica for the efficient production of glycosylated astaxanthin. Introducing zeaxanthin glucosyltransferase CrtX from Pantoea ananatis into an astaxanthin-producing strain enabled the synthesis of astaxanthin glucosides, confirmed by HR-ESI-MS, 1H NMR, and 2D NMR. Engineering UDP-glucose metabolism by reducing competing pathways and enhancing UDP-glucose biosynthesis improved the astaxanthin glucoside production. The best strategy comprised inactivation of the glycogen synthase gene GSY1 combined with multicopy integration of PGM1 (phosphoglucomutase) and UGP1 (UDP-glucose pyrophosphorylase), achieving 17.6 mg/L of astaxanthin monoglucoside and 25.1 mg/L of diglucoside in test-tube cultures. Fed-batch fermentation with glucose yielded 141.6 mg/L of astaxanthin monoglucoside. When corn syrup was used as a low-cost, sustainable carbon source, the production shifted toward astaxanthin diglucoside, reaching 134.3 mg/L. These results represent the highest glycosylated astaxanthin titers reported to date.