Lipase-catalyzed Synthesis Of Fatty Acid Esters In Organic Solvent And Their Antimicrobial Properties

Fatty acid esters are surfactants with fatty acids act as a hydrophobic group. They are widely used in the food, cosmetic, detergent and pharmaceutical industry because of their strong emulsifying capacity, nontoxicity and biodegradability. In addition, fatty acid esters also possess lubricating, deterging, foaming, anti-ageing, anti-crystallizing and anti-microbial property. They are recommended food additives by FAO and WHO.In the present study, reaction conditions for lipase catalyzed synthesis of sugar laurate esters and glycerol fatty acid esters were optimized, then purification of these monoesters and the measurement of their antibacterial property were carried out accordingly.Firstly, batch synthesis of lauroyl N-acetylamino glucose was optimized by studying the factors influencing the reaction including the organic solvent used, the reaction temperature and time, molar ratio of fatty acid and glucose, the amount of lipase and molecular sieve used etc. Results showed the optimized synthesis conditions in a mixed tert-butanol and DMF (7:3) solvent were as follows: the molar ratio of lauric acid to N-acetylamino glucose, 3:1; the amount of molecular sieve used, 70 g/L; the amount of lipase used, 20g/L; the shaking speed of the water bath, 150r/min; the reaction temperature, 60℃; the reaction time,48h.The conversion ratio of the lauroyl N-acetylamino glucose monoester reached 76.9% under this optimized condition.Furthermore, a series of carbohydrate laurate esters including glucose monolaurate, fructose monolaurate, N-acetylamino glucose monolaurate, sucrose monolaurate and mannose monolaurate, and glycerol fatty acid esters including glycerol monocarprate, glycerol monolaurate and glycerol monomyristate were synthesized in the mixed tert-butanol and DMF(7:3) solvent catalyzed by lipase Novozym435. The reaction products of the monoesters were identified by LC/MS and HPLC. The eluting conditions of the different sugar esters and glycerol fatty acids esters were tested and optimized. After purification, the purity of the monoesters were analyzed by HPLC-ELSD and LC-MS.The inhibition ability of the five purified sugar laurate monoesters against bacteria, yeast and mold were investigated at different concentrations. And the minimum inhibitory concentration (MIC) of all fatty acid monoesters against bacteria, yeast and mold were tested. The influences of concentration, pH, different hydrophobic groups and hydrophilic group on the antimicrobial ability of fatty acids esters were studied.