Sustainable synthesis of biosurfactants from renewable resources

SFAEs (Sugar-Fatty Acid Esters) are a class of non-ionic surfactants characterized by excellent surface and interfacial tension reduction capability, low toxicity and biodegradability. Depending on their carbon chain length and the nature of the sugar head group, SFAEs can cover a wide range of hydrophilic-lipophilic balance (HLB) values, which result in tunable surfactant properties. Moreover, SFAEs can be obtained from renewable resources (i.e. industrial waste and biomass) by enzymatic and/or chemoenzymatic approaches, thus answering the need for sustainable and circular chemistry [1]. In this context, a small library of SFAEs were prepared by the lipase-catalyzed esterification of isomeric mixtures of alkyl glycosides (namely α-/β-d-glucosides and α-/β-d-galactosides) with molten fatty acids (lauric, palmitic and stearic acid), using CalB (Novozym® 435) as biocatalyst in an easily scalable solvent-free system. Conversion of glucose and galactose into alkyl glycosides before the esterification reaction played a key role in circumventing the striking different solubility of the two reagents. The physico-chemical properties of the synthesized tensides (interfacial tension features, W/O emulsification capability and W/O stability over time) were then finely investigated [2]. References [1] a) I.J.A. Baker et al., J. Surfactant Deterg. 3 (2000) 1-11; b) H.M. El-Laithy et al., Eur. J. Pharm. Biopharm. 77 (2011) 43-55; c) N.S. Neta et al., Crit. Rev. Food Sci. Nutr. 55 (2015) 595-610. [2] a) S. Sangiorgio et al., Colloids Interface Sci. Commun. 48 (2022) 100630; b) R. Semproli et al., ChemPlusChem 88 (2023) e202200331.