Efficient Extraction and Recovery of Astaxanthin from Bacterial Sources Using Fatty Acids

Abstract

Natural astaxanthin is heavily preferred over synthetic alternatives for both food and pharmaceutical applications due to its superior bioactivity. However, conventional recovery methods rely on toxic volatile organic solvents (VOCs) and energy-intensive thermal distillation. This study presents an integrated, nonthermal biorefining strategy for Paracoccus carotinifaciens using short- and medium-chain food-grade fatty acids. The proposed “one-pot” process utilizes the pH-controlled dissociation of these solvents to simultaneously extract and recover the ketocarotenoids in a single vessel. Propanoic acid achieved the highest relative initial extraction efficiency (∼100%), outperforming acetic (88%) and butanoic (83%) acids. Subsequent alkaline phase-shifting triggered a thermodynamic “dissolution-to-precipitation” switch, yielding quantitative recovery (>98%) of carotenoids from propanoic, butanoic, and hexanoic acid solutions. High-performance liquid chromatography suggested the preliminary structural preservation of a highly enriched fraction of astaxanthin, adonirubin, and canthaxanthin relative to the starting bacterial biomass. Furthermore, a conceptual proof of principle of solvent recovery was demonstrated with hexanoic acid, achieving 80% bulk solvent recovery strictly via phase separation. This methodology completely eliminates VOCs and inherently bypasses thermal degradation, offering a highly sustainable, scalable route for industrial microbial pigment production.