Sugar fatty acid esters (SFAEs) are biocompatible nonionic surfactants with broad applications in food, cosmetic, and pharmaceutical industries. They can be synthesized enzymatically with many advantages over their chemical synthesis. In this study, SFAE synthesis was investigated by using two reactions: (1) transesterification of glucose with fatty acid vinyl esters and (2) esterification of methyl glucoside with fatty acids, catalyzed by Lipozyme TLIM and Novozym 435 respectively. Fourteen ionic liquids (ILs) and 14 deep eutectic solvents (DESs) were screened as solvents, and the bisolvent system composed of 1-hexyl-3-methylimidazolium trifluoromethylsulfonate ([HMIm][TfO]) and 2-methyl-2-butanol (2M2B) was the best for both reactions, yielding optimal productivities (769.6 and 397.5 µmol/h/g, respectively) which are superior to those reported in the literature. Impacts of different reaction conditions were studied for both reactions. Response surface methodology (RSM) was employed to optimize the transesterification reaction. Results also demonstrated that as co-substrate, methyl glucoside yielded higher conversions than glucose, and that conversions increased with an increase in the chain length of the fatty acid moieties. DESs were poor solvents for the above reactions presumably due to their high viscosity and high polarity.

Background: As nonionic surfactants derived from naturally renewable resources, sugar fatty acid esters (SFAEs) have been widely utilized in food, cosmetic, and pharmaceutical industries. Results:In this study, six enzymes were screened as catalyst for synthesis of glucose laurate. Aspergillus oryzae lipase (AOL) and Aspergillus niger lipase (ANL) yielded conversions comparable to the results obtained by commercial enzymes such as Novozyme 435 and Lipozyme TLIM. The productivity obtained by AOL catalysis in anhydrous 2-methyl-2-butanol (2M2B) (38.7 mmol/L/h and 461.0 μmol/h/g) was much higher than the other literature results. Factors affecting the synthetic reaction were investigated, including water content, enzyme amount, substrate concentrations and reaction temperature. The process was greatly improved by applying the Box-Behnken design of response surface methodology (RSM). Solubilities of glucose in 14 different organic solvents were determined, which were found to be closely associated with the polarity of the solvents. Conclusions:Aspergillus oryzae lipase is a promising enzyme capable of efficiently catalyzing the synthesis of sugar fatty acid esters with excellent productivity.

As nonionic surfactants derived from naturally renewable resources such as sugars and fatty acids, sugar fatty acid esters have been widely utilized in food, cosmetic and pharmaceutical industries. Our present study has demonstrated that the inexpensive and halogen-free tetraalkylammonium salts (e.g., [Bu 4 N][Ac], [Et 4 N][Ac] and [Me 4 N][Ac]) can act as dual solvents-catalysts for regioselective acylation to produce glucose laurate. This non-enzymatic synthesis can proceed under mild conditions with high specificity, and the conversions obtained were superior to that when an enzyme catalyst (lipase, EC 3.1.1.3) was added. A higher yield was obtained in the ammonium salt with a longer alkyl chain on the cation, while no product was obtained in [Bu 4 N][HSO 4 ] and [Bu 4 P][Ac]. A reaction mechanism has been proposed, which is supported by phase-transfer catalysis and law of matching water affinity.