Characterization of enzymatically prepared sugar medium-chain fatty acid monoesters.

Sugar medium-chain fatty acid esters are a new type of biodegradable, non-toxic, non-irritant and non-ionic surfactant with proven antimicrobial activity. Various sugar medium-chain fatty monoesters were prepared enzymatically using Lipozyme TLIM in organic solvent. Properties such as surface tension, antimicrobial activity, and ability to foam, emulsify and stabilize emulsions at room temperature were evaluated to conduct systematic studies on the structure-function relationships of these compounds. Results showed that all monoesters displayed good surface activity properties. In particular, sucrose monolaurate was the most excellent surfactant among 12 monoesters. Sugar monoesters containing C8 to C12 alkyl chains showed a broad spectrum of increasing antimicrobial activity. All tested monoesters were more effective against Staphylococcus aureus (Gram-positive bacterium) than Escherichia coli O157:H7 (Gram-negative bacterium). Methyl α-d-glycoside monoesters were the most effective, whereas raffinose monoesters possessed poor antimicrobial activity. Generally, the length of fatty acid chain (hydrophobic group) and sugar groups (hydrophilic group) for sugar medium-chain fatty acid monoesters both affected the surface properties and antimicrobial activities.