Highly efficient and solvent-free biocatalytic synthesis of castor oil-based surfactants via by Eversa® Transform 2.0: Reaction dynamics and product characterization

Monoglycerides and diglycerides are high value-added sustainable bio-surfactants. However, their synthesis is limited due to the high energy consumption of chemical catalysts and mass transfer limitation of the immobilized enzymes. To circumvent these bottlenecks, a highly efficient, solvent-free strategy was established for the biocatalytic synthesis of bio-based surfactants through the glycerolysis of castor oil using liquid lipases. Results showed that Eversa® Transform 2.0 was the best biocatalyst. Under the optimal conditions (29 °C, 99 min, 1:6 oil-to-glycerol ratio), 42.30 ± 2.11% MAG yield and 49.84 ± 0.58% DAG yield were achieved. An activation energy 31.24 kJ/mol and a K m value of 0.701 were obtained via kinetic analysis. Furthermore, a two-stage molecular distillation was engineered to successfully fractionate the crude mixture into customized products: a DAG-enriched surfactant (DSP, containing 49.90 ± 1.00% DAGs and 42.30 ± 2.10% MAGs) and a high-purity MAG-enriched surfactant (MSP, containing 91.30 ± 1.70% MAGs and 4.90 ± 1.30% DAGs). Finally, molecular docking confirmed that the ET 2.0 lipase constructed a multidimensional hydrophobic network primarily via the key amino acid residues (e.g., Leu206, Trp89, and Phe113). Triricinolein is stably bound by this hydrophobic configuration, which precisely positions the target ester bond near the catalytic center to promote efficient cleavage and biocatalysis.