Synthesis of bio-based surfactants from renewable raw materials: a sustainable chemoenzymatic approach

Over the past decades, multiple concerns about surfactants derived from petroleum precursors have increased the demand for more environmentally friendly alternatives. In this context, Sugar fatty Acid Esters (SFAEs) have emerged as a promising class of non-ionic surfactants matching excellent emulsifying, stabilizing and detergency properties with striking advantages over their conventional counterparts (e.g. they are odorless, tasteless, skin-compatible, non-toxic, fully biodegradable and non-harmful to the environment).1 Nonetheless, currently established industrial syntheses of SFAEs require harsh reaction conditions, usually resulting in complex mixtures of isomers and by-products.2 Enzymatic strategies represent therefore a potential alternative to circumvent these drawbacks.3 Following the principles of green chemistry and circular economy, a library of SFAEs were prepared by a two-step chemoenzymatic strategy, starting from fatty acids and glucose/galactose (Figure 1). Both sugars can be obtained by enzymatic hydrolysis of lactose, the main components of cheese whey permeate (CWP) as renewable agricultural biomass. Owing to the strikingly different solubilites of fatty acids and sugars, the latter were converted into mixtures of their alkyl glycosides (α- and β-D-glucosides/galactosides) by glycosylation with naturally occurring alcohols prior to the esterification step. Cheap, safe and recyclable catalysts were employed in both reactions (Amberlyst® 15 and Novozym® 435 (CalB), respectively). The influence of the sugar polar head (glucose vs galactose), the tail chain length (C12 vs C16 vs C18) and the ring size (pyranosides vs furanosides) on the physico-chemical properties of the synthesized tensides (interfacial tension features, W/O emulsification capability and W/O stability over time) was evaluated.4 Figure 1. Chemoenzymatic synthesis of SFAEs from CWP and fatty acids. Acknowledgments This work was financially supported by Cariplo Foundation (Italy) (call: “Circular Economy for a sustainable future 2020”, project BioSurf, ID 2020-1094, https://www.biosurfproject.it/). M.S.R. is supported by the project NODES which has received funding from the MUR – M4C2 1.5 of PNRR with grant agreement no. ECS00000036. References 1. a) H. M. El-Laithy et al., Eur. J. Pharm. Biopharm. 2011, 77, 43-55; b) N.S. Neta et al., Crit. Rev. Food Sci. Nutr. 2015, 55, 595-610. 2. N. R. Khan et al., Process Biochem. 2015, 50, 1793-1806. 3. a) R. Hausmann et al., Biosurfactants for the Biobased Economy, Springer Nature Switzerland AG, Cham, 2022; b) J. W. Agger et al., Curr. Opin. Biotechnol. 2022, 78, 102842. 4. a) S. Sangiorgio et al., Colloids Interface Sci. Commun. 2022, 48, 100630; b) R. Semproli et al., ChemPlusChem. 2023, 88, e202200331.