Deep eutectic solvents as an emerging platform for microbial carotenoids extraction: State of the art, prospects, and challenges

Microbial carotenoids are promising alternatives to synthetic ones in food, cosmetics, nutraceuticals, and pharmaceuticals, offering antioxidant, anti-aging, and anti-cancer benefits. However, the conventional extraction methods commonly used for carotenoids often rely on petrochemical solvents, raising environmental and health concerns. In this context, deep eutectic solvents (DESs) have emerged as sustainable alternatives due to their low toxicity, cost-effectiveness, ease of preparation, biodegradability, recyclability, and excellent compatibility. This review discusses the history, classification, toxicity, and biodegradability of DESs, along with recent advances in microbial carotenoid recovery, focusing on pretreatment, extraction, and underlying mechanisms, followed by the discussions on sustainability assessment and current technological challenges. While DES-based processes show significant potential within green chemistry, their feasibility for large-scale, commercial applications remains to be validated. By providing a critical overview, this study aims to guide further research and development in eco-friendly downstream processing of microbial carotenoids, bridging the gap between scientific investigation and industrial practice.