Optimization of Lipase Activity in Aspergillus niger C2J6 Whole Cells Using Choline Chloride Ethylene Glycol Deep Eutectic Solvent

Deep eutectic solvents (DES), recognized as tunable green solvents, show significant potential for enhancing enzyme activity in biocatalytic applications. This study investigated the effect of choline chloride–ethylene glycol DES on the lipase activity of Aspergillus niger C2J6 whole cells, employing a self-isolated endophytic strain. By varying the molar ratio (1:2–1:4) and water content (0–80%), the highest lipase activity (142.31%) was observed at a 1:1.55 molar ratio with 46% water content. Mathematical models were developed to connect DES composition with key properties, including surface tension, conductivity, density, viscosity, refractive index, polarity, and water activity. Statistical analysis revealed that among the physicochemical properties of DES, polarity exhibited the most significant impact on enzymatic activity, followed by viscosity, surface tension, and conductivity. This study provides valuable insights for designing optimized DES systems to improve biocatalytic efficiency and precision.