Enzymatic Selective Synthesis Of Monolauroyl Maltose

Sugar fatty acid esters have been widely used in foods, medicines and cosmetics by taking advantage of their particular properties, including nontoxic, biodegradable and great interficial properties. Sugar mono- and di- esters have obviously different physicochemical characterization and functional properties, so how to control the reaction condition to synthesize the production needed was a focus, difficulty and common problem. After the products focusing on maltose and lauric acid were purified and identified as monolauroyl maltose and dilauroyl maltose, the way to selective synthesis monolauroyl maltose was discussed, and the main parameters that need to be considered were ascertained. Water solubility, interficial properties, the thermal behaviour, rheology properties, anti-aging property and antimicrobial activity of monolauroyl maltose were studied and compared with other sugar esters. The main conclusion of this study included:Silica gel column chromatography with mobile phase of chloroform-methanol (4:1, v/v) for maltose ester at 18 ml/h was applied. The condensed products catalyzed by Nov 435 were analyzed by IR, MS ,1H NMR and 13C NMR, and then identified to be 6'-O-lauroylmaltose and 6,6'-di-O-lauroylmaltose.For monolauroyl maltose, the highest conversion of 93 % and concentration of 23.35 mmol/l were obtained in acetone when the condensation was carried out at 50℃for 72 hours with 20 g/l of lipase, 25 mmol/l of maltose, 75 mmol/l lauric acid and 60 g/l of 3 A molecular sieves in a batch reactor. Temperature was the major factor affecting the concentration of monolauroyl maltose, while maltose concentration was the major factor affecting the conversion of monolauroyl maltose. The conversion of monolauroyl maltose was obviously higher compared with monolauroyl sucrose at condition discribed above. The conversion of maltose monoesters was decreased when the fatty acid chain length increased. The activation energy of monolauroyl maltose enzymatic synthesis by Nov 435 was 23.07 kJ/mol.Monolauroyl maltose could be selectively synthesized in a continuous stirred tank reactor (CSTR). The highest concentration of monolauroyl maltose at 28 mmol/l in acetone was obtained when maltose was added at 4 g/d and the molar ratio of lauric acid to maltose was fixed at 4:1 at a flow rate of 0.15 ml/min effluent without supplement of fresh molecular sieve. The average yield of monolauroyl maltose was 10.12 g/l·d during 10 days operation. Several extraction-centrifuging were used to purify the product and recover the lauric acid unreacted, and which made it possible to prepare monolauroyl maltose in large scale. The separating process was as followed: after 25 ml effluent was concentrated, 12.5 ml hexane was added to the precipitation for the first extraction-centrifuging, then 2.5 ml hexane was added for the second and third extraction-centrifuging, the final product was purified to be 94% of monolauroyl maltose with 76 % of retention. HLB values of maltose monoesters and sucrose monoesters, were from 16.1 to 18.2, and could be used for the preparation of nonionic O/W microemulsions.The DSC revealed that the tested sugar esters could be recrystalized, except for monostearoyl sucrose. The recrystallization was a mixture of crystaline and amorphous state, and differred from the initial state. A model nonionic water-in-oil microemulsion system based on sugar monoester/1-butanol/n-hexandecane (1.5:1:1) could bound 16% to 20% with water.Emulsions (paraffin-water) produced by maltose monoesters and sucrose monoesters, water solution of monolauroyl maltose and monolauroyl sucrose were pseudoplastic fluid, while water solution of monomyristroyl maltose, monomyristroyl sucrose monopalmitroyl maltose, monopalmitroyl sucrose, monostearoyl maltose and monostearoyl sucrose were newtonian flow.The RVA and DSC showed that maltose monoesters and sucrose monoesters at 0.09% bulk concentration could improve the hot stability of starch suspension and prolong the starch paste aging during storage. Monolauroyl maltose and monolauroyl sucrose inhibited the growth of Bacillus cereus, B. coagulans, B. subtili, Geobacillus stearothermophilus, Escherichia coli and Staphylococcus aureus at 0.09% bulk concentration.Among the tested maltose monoesters and sucrose monoesters, monolauroyl maltose led to greatest interficial properties and antimicrobial activity, while monostearoyl maltose and monostearoyl sucrose had the greatest anti-aging property.