Optimization of microalgae lipid extraction for sustainable omega-3 production: Integrating microwave-assisted cell disruption, wet biomass processing, and ethanol as a green solvent

Abstract

Microalgae-derived lipids offer a sustainable alternative to conventional omega-3 sources, yet industrial-scale production remains constrained by energy-intensive downstream processing and reliance on toxic solvents. This study systematically optimised three critical downstream steps: cell disruption, biomass drying, and lipid extraction, for four microalgae species cultivated in Sri Lanka: Chlorella vulgaris, Nannochloropsis oculata, Chaetoceros calcitrans, and Thalassiosira pseudonana. Three cell disruption methods (microwave, autoclave, and osmotic shock) were compared, followed by evaluation of wet versus oven-dried biomass and assessment of ethanol as a green solvent alternative to the conventional Bligh & Dyer method. Microwave-assisted disruption yielded the highest lipid recovery across all species (10.3–22.5% DW), significantly outperforming autoclave treatment (p < 0.05). Lipid yields from wet and dry biomass were not significantly different (p > 0.05) for any species, indicating that the energy-intensive drying step can be eliminated without compromising yield. Ethanol extraction yielded lower total lipid recovery (55.3–83.5% relative to Bligh & Dyer) but selectively enriched polyunsaturated fatty acids, with total unsaturated fatty acid content reaching 74.4% in T. pseudonana. Nannochloropsis oculata exhibited the highest lipid content (22.5% DW) and a favourable fatty acid profile, making it the most promising candidate for omega-3 production. These findings demonstrate that combining microwave-assisted disruption with wet biomass processing and ethanol extraction offers a cost-effective, energy-efficient, and food-safe protocol for microalgae lipid recovery, with strong potential for industrial adoption in tropical developing nations.