Supercritical carbon dioxide extraction of astaxanthin from Corynebacterium glutamicum

Astaxanthin, a red carotenoid with potent antioxidant properties, holds significant value in the feed, cosmetics, and nutraceutical industries. While traditionally sourced from microalgae, Corynebacterium glutamicum, a well-established industrial microorganism, has been engineered to serve as an efficient host for astaxanthin production. As astaxanthin integrates into the cellular membrane, effective extraction methods are essential to access this valuable compound. In this study, a sustainable batch extraction process using supercritical carbon dioxide (scCO₂) as a green solvent was developed. The effects of cosolvent concentration (0-9% (w/w)), temperature (50-75 °C), and pressure (450-650 bar) were investigated with regard to the extraction yield. An optimized extraction was achieved with 9% (w/w) ethanol as a cosolvent, at 68 °C and 550 bar, allowing the extraction of 67.5 ± 3.7% of the cellular astaxanthin within 0.5 h. Prolonging the extraction time further increased the recovery to 93.3%, which is comparable to processes that have been established for the extraction of astaxanthin from microalgae and yeast. This approach provides a scalable and environmentally friendly solution for industrial astaxanthin recovery.