Molecular Evaluation of Deep Eutectic Solvents for Wet Algae Lipid Extraction and Biofuel Production

Abstract Microalgae represent promising feedstocks for biofuel production, yet cell-wall disruption remains a critical bottleneck for scaling up lipid extraction. This study evaluates four cholinium-based ionic liquids (ILs) and deep eutectic solvents (DESs) as green, energy-efficient pretreatment agents to facilitate the lipid release from Chlorella vulgaris under wet conditions. A geranic acid-based DES (CG 1-2 DES) was identified as the optimal agent, demonstrating direct wet biomass extraction with substantial process energy savings at comparable overall lipid yields. To minimize the energetic costs of biomass drying and reduce CO2 emissions, lipid extraction was evaluated under wet conditions by using a one-pot method for DES recycling. FTIR spectroscopy and mesoscopic molecular dynamics simulations suggested the underlying mechanism: CG 1-2 DES disrupts cell wall lipids while maintaining specific miscibility to phase-separate from the product lipids, with water acting as a key process parameter that weakens hydrogen bonding and lowers mixture viscosity. These insights highlight key operational differences from conventional dry extraction and the previous use of CG 1-2 DES in skin permeation applications. Ultimately, utilizing IL/DES systems for wet extraction offers a sustainable, cost-effective pathway for biofuel processing where integrated experimental and computational screening can further accelerate material optimization.