Improving the environmental compatibility of enzymatic synthesis of sugar-based surfactants using green reaction media

Abstract

The enzymatic synthesis of sugar-based surfactants is often performed in non-conventional media that do not meet any longer the current environmental acceptability, especially for biodegradability and cytotoxicity. In this work, we propose innovative sustainable routes by replacing the current reference organic solvent, 2-methyl-2-butanol (2M2B) by either 2-methyltetrahydrofuran (MeTHF), an agrosolvent, or 2-methyltetrahydrofuran-3-one (MeTHF-3-one), a food-grade ingredient used as solvent. These two neoteric solvents were thus evaluated as reaction media via a lipase-catalyzed esterification of glucose by lauric acid and revealed a novel matter of interest. The regioselectivity of the reaction was mainly directed toward the primary alcohol of glucose maintaining the end-product obtained in 2M2B: D-glucose-6-O-laurate. The PLS-Surface Response Design evidenced enzymatic performances in ester production of 48% in MeTHF and 79% in MeTHF-3-one. The latter solvent resulted not only in better yields compared to 2M2B, but also in an increased enzymatic stability, allowing better reuse of the catalyst. MeTHF-3-one has been shown to be readily biodegradable according to OECD standards. Herein, this solvent has been substantiated for the first time as a green medium in an efficient, selective and sustainable enzymatic synthesis of sugar esters.