Tailored natural deep eutectic solvents for isolation of astaxanthin from Paracoccus carotinifaciens and one-pot synthesis of functional ingredients for biotechnological applications.

The development of sustainable and multifunctional extraction systems is essential for advancing natural health products derived from microbial sources. Here, menthol-based Natural Deep Eutectic Solvents (NADES) were evaluated for the extraction and formulation of astaxanthin-rich extracts (ARE) from Paracoccus carotinifaciens. Binary mixtures of DL-menthol with carboxylic acids or alcohols were designed to act simultaneously as eco-friendly solvents and bioactive formulation components. COSMO-SAC predictions indicated DL-menthol and acetic acid as the most suitable pair, which was confirmed experimentally with extraction yields of approximately 1.5 mg/mL. Storage stability studies showed that low temperature and dark conditions effectively preserved ARE, while heat and light accelerated degradation. A one-pot bioprocess was established to integrate extraction, selective acetic acid recovery, and direct formulation, enabling the production of a mint-flavored chewable antioxidant supplement. In vitro digestion assays revealed decreased ARE stability during the intestinal phase, indicating the need for further formulation optimization. Overall, menthol-based NADES present a sustainable and multifunctional platform for carotenoid extraction and ingredient development, supporting the replacement of conventional organic solvents in natural product bioprocessing.