Growth inhibitory properties of lactose fatty acid esters.

Sugar esters are biodegradable, nonionic surfactants which have microbial inhibitory properties. The influence of the fatty acid chain length on the microbial inhibitory properties of lactose esters was investigated in this study. Specifically, lactose monooctanoate (LMO), lactose monodecanoate (LMD), lactose monolaurate (LML) and lactose monomyristate (LMM) were synthesized and dissolved in both dimethyl sulfoxide (DMSO) and ethanol. Minimum inhibitory concentrations (MIC) and minimum bactericidal concentrations (MBC) were determined in growth media. LML was the most effective ester, exhibiting MIC values of <0.05 to <5 mg/ml for each Gram-positive bacteria tested (, , , , , and ) and MBC values of <3 to <5 mg/ml for , , , and . LMD showed MIC and MBC values of <1 to <5 mg/ml for , , , , and , with greater inhibition when dissolved in ethanol. LMM showed MIC and MBC values of <1 to <5 mg/ml for , , and . LMO was the least effective showing a MBC value of <5 mg/ml for only , though MIC values for and were observed when dissolved in DMSO. and were the most susceptible to the lactose esters tested, while and were the most resilient and no esters were effective on . This research showed that lactose esters esterified with decanoic and lauric acids exhibited greater microbial inhibitory properties than lactose esters of octanoate and myristate against Gram-positive bacteria.