EVALUATION OF DIFFERENT SOLID-LIQUID EXTRACTION OF β-CAROTENE PRODUCED BY Rhodotorula glutinis

The production and extraction of β-carotene from microbial sources like the yeast Rhodotorula glutinis have gained significant interest due to its possible applications in food, pharmaceuticals, and cosmetics. However, these compounds are produced intracellularly, and their recovery from microbial biomass represents a critical step in the process. Generally, Solid-liquid extraction (SLE) is used as the first step of recovery and optimizing the solvent system can enhance yield and efficiency. This study aimed to compare two SLE methods for β-carotene extraction from R. glutinis cultivated in a synthetic medium. The medium consisted of KH₂PO₄ (0.52 g/L), MgSO₄·7H₂O (0.52 g/L), NH₄NO₃ (4 g/L), malt extract (7.93 g/L), glucose (10 g/L), and Tween 80 (1.71% v/v). Cultivation was carried out in 500-mL Erlenmeyer flasks with a 50 mL working volume under conditions of pH 5, 30 °C, 300 rpm agitation, and 96 h incubation. SLE was performed at a standardized solid-liquid ratio (SLR) of 0.025 g/mL using two procedures: (a) a conventional solvent system involving dimethyl sulfoxide (DMSO), acetone, and recovery in hexane, and (b) an alternative method using acetone with vortex-assisted glass bead disruption followed by recovery in ethanol. β-carotene concentration was quantified using calibration curves specific to each recovery solvent. Results demonstrated that the DMSO/acetone/hexane system achieved a significantly higher β-carotene yield (688.10 ± 15.17 µg/L) compared to the acetone/ethanol method (592.29 ± 7.93 µg/L), representing a 16.8% increase in recovery efficiency. The superior performance of the DMSO-based system may be attributed to its enhanced cell membrane disruption capability, facilitating better carotenoid release, whereas mechanical disruption with glass beads proved less effective. These findings highlight the critical role of solvent selection in SLE, with DMSO proving more efficient than physical methods for β-carotene extraction from R. glutinis, however less sustainable. The study underscores the importance of optimizing extraction protocols to maximize pigment recovery, with potential implications for industrial-scale processes. Further research could explore alternative solvents or combined disruption techniques to improve cost-effectiveness and sustainability while maintaining high extraction yields.