Enzymatic synthesis and characterization of galactosyl monoesters

• An efficient synthesis of glucosyl fatty acid-amino acid esters is reported.
• Good surface activity performances are proved.
• Chemical stability is reflected in solution of weak acid, weak base or neutrality.
• The micellization is spontaneous through entropy-driven process.

Enzyme-catalyzed synthesis of several fatty acyl-amino acid esters based on d-galactose, as well as their chemical evaluation, was performed. These novel galactosyl fatty acyl-amino acid monoesters were synthesized by utilizing lipase from lipozyme TL IM in tert-butanol with d-galactose and fatty acyl-amino acids as starting materials. The products were characterized by 1H NMR, 13C NMR and MS analysis. In addition, their primary physical properties, such as hydrophilic-lipophilic balance (HLB), critical micellar concentration (CMC), solubility in water, maximum surface excess (Γmax), and minimal surface tension (Amin) were measured. The experimental results showed that their CMC values are between 5 and 0.4 mM. The HLB values of galactosyl esters 15–17 indicate that they are useful as oil-in-water emulsions or detergents, whereas 18–22 can be employed as water-in-oil emulsifiers or wetting agents.

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