Sugar-based surfactants: chemoenzymatic synthesis and interfacial properties evaluation

Sugar Fatty Acid Esters (SFAEs) are a family of non-ionic surfactants widely used as emulsifiers in many market sectors (i.e. food and cosmetic industry). These tensides are becoming of great interest because, among other features, they are fully biodegradable and can be produced from renewable resources,[1] such as cheese whey permeate (the main waste stream of the dairy industry). The current industrial synthesis requires harsh reaction conditions which result, in most cases, in complex mixtures. An alternative and more sustainable approach deserves to be investigated. Indeed, SFAEs can be produced through a solvent-free esterification reaction between a modified sugar and a molten fatty acid, catalyzed by a lipase.[2] Lactose, the main component of whey permeate, was used as the starting material to synthesize butyl-β-D-galactopyranoside through a transglycosylation reaction catalyzed by the immobilized β-galactosidase from Aspergillus oryzae in a ternary system composed of n-BuOH/acetone/McIlvane buffer 50 mM pH 4.5 (50/30/20).[3] Glucose, the by-product of the transglycosylation reaction, was converted into isomeric mixtures of glucosides by reaction with a number of naturally occurring alcohols in the presence of Amberlyst® 15. Resulting glucosides were submitted to a Novozyme® 435-catalyzed esterification with lauric, palmitic, and stearic acid in a solvent-free system, thus affording a set of SFAEs. Moreover, the sunflower oil/water interfacial tension (IFT) values by varying the amount of the 6-O-lauryl, 6-O-palmitoyl and 6-O-stearyl-1-O-butyl glucosides were measured by a Gibertini tensiometer exploiting the Du Noüy ring method. All the surfactants allowed the IFT reduction from 26 mN m-1 (sunflower oil/water interface) to a value around 3 mN m-1, corroborating the actual surface properties of the tested sugar-based molecules.[4] This abstract reports the preliminary results of the BioSurf project funded by Cariplo Foundation (Italy): “Circular Economy for a sustainable future – Call 2020”, ID 2020–1094, 06/01/2021-11/30/2023. References [1] N.S. Neta, J.A. Texteira, L.R. Rodrigues, Crit. Rev. Food Sci. Nutr., 2015, 55, 595-610. [2] N. Sarmah, D. Revathi, G. Sheelu, K. Yamuna, Rani, S. Sridhar, V. Mehtab, C. Sumana, Biotechnol. Prog., 2018, 34, 5-28. [3] D. Ahumada, F. Arenas, F. Martinez-Gòmez, C. Guerrero, A. Illanes, C. Vera, Front. Bioeng. Biotechnol., 2020, 8, 859. [4] L. Bai, W. Xiang, S. Huan, O.J. Rojas, Biomacromolecules, 2018, 19, 5, 1674-168