Optimization of a green method for extracting lipids from the red yeast Rhodotorula mucilaginosa: Partial characterization of oil and biomass

This study aimed to optimize a greener extraction protocol for carotenoid-rich microbial oil from R. mucilaginosa , employing less hazardous solvents, and to characterize the lipid fraction, integral, and residual biomass. A Plackett-Burman design was applied to screening process variables, followed by optimization using a Response Surface Methodology. The optimized and validated method, based on an ethyl acetate solvent system yielded 26.0% lipids recovery, and achieved a score of 0.62 in the GREEnness metric, indicating a more sustainable process. The microbial oil obtained had a high-quality profile, composed of 75% monounsaturated fatty acids (MUFAs) and polyunsaturated fatty acids (PUFAs). Its physicochemical characterization revealed an average molecular weight for triacylglycerols of 902.55 g/mol, iodine index of 74.00 g I₂/100 g, saponification index of 185.60 mg KOH/g, free acidity of 8.42%, peroxide index of 2.61 mEq O₂/kg, and a ¹H NMR-determined olefinic-to-aliphatic proton ratio of 2.43. The total carotenoid content in the oil fraction was estimated in 48.80 µg/g. The integral biomass contained 26.3% lipids, 16.0% proteins, and 55.8% carbohydrates. The residual biomass content was 67.8% carbohydrate and 10.3% protein. This study demonstrates an efficient and less toxic extraction strategy, contributing to the development of a more sustainable and economically viable R. mucilaginosa biorefinery platform. • Rhodotorula mucilaginosa CCT 7688 produced carotenoid-rich oil. • The microbial oil was rich in MUFAs and PUFAs, with nutritional potential. • The residual biomass had a high protein content. • A solvent mixture of acetic acid, ethanol, and ethyl acetate recovery 26.0% lipids. • Process optimization via Plackett-Burman and CCRD improved green extraction.