Lipase‐Catalyzed Synthesis and Physicochemical Characterization of Oleoyl Monoethanolamide From Oleic Acid

This study reports the enzymatic synthesis of oleoyl monoethanolamide from oleic acid and ethanolamine using lipase as a biocatalyst, followed by optimization and comprehensive physicochemical characterization. The highest conversion of 89.22% was achieved at 60°C, 8 h reaction time, a 2.5:1 ethanolamine‐to‐oleic acid molar ratio, and 10% (w/w) enzyme concentration. Structural confirmation was conducted using FTIR, which revealed the disappearance of the carboxylic acid CO band and the emergence of amide I and amide II signals. Further evidence from 1 H‐NMR and 13 C‐NMR indicated the loss of carboxyl proton signals, the appearance of amide NH resonances, and a shift in carbonyl carbon from 180.34 ppm (acid) to 176.08 ppm (amide), confirming successful amidation. Physicochemical evaluation demonstrated a substantial reduction in acid value from 196.91 to 21.61 mg KOH/g and saponification value of 14.13 mg KOH/g, indicating efficient conversion of oleic acid. The product presents a calculated HLB of 6.9, suggesting lipophilic characteristics suitable for water‐in‐oil emulsification. Interfacial tension decreased from 11.04 to 4.23–4.30 mN/m at higher surfactant concentrations, with a critical micelle concentration (CMC) of approximately 0.35%. These results highlight the potential of enzymatically synthesized oleoyl monoethanolamide as an effective bio‐based nonionic surfactant.