The BioSurf project: a biocatalytic approach to the synthesis of bio-based surfactants through the valorization of dairy industry waste

Emerged in recent decades as eco-friendly alternatives to petroleum-derived surfactants, Sugar Fatty Acid Esters (SFAEs) match excellent emulsifying, stabilizing and detergency properties with remarkable benefits over their ionic conventional counterparts (e.g. non-toxicity, skin-compatibility, tastelessness, odorlessness, full biodegradability and environmental harmlessness) [1]. In the framework of a strive to fulfil the principles of circular economy, the BioSurf project aims at accomplishing an integrated platform for the sustainable production of bio-based surfactants from renewable agricultural resources [2], at the same time circumventing the major downsides of currently established industrial syntheses of SFAEs, e.g. complex products and by-products mixtures arising from harsh reaction conditions (hazardous solvents, high temperatures, strong and poorly selective acid or base catalysts) [3]. The merging of chemical synthetic routes and enzymatic strategies indeed appears to be a promising alternative to simplify both product synthesis and downstream [4]. More in detail, a two-step chemoenzymatic strategy was devised to synthesize a library of SFAEs, starting with glucose/galactose and fatty acids from biomass to obtain the surfactant polar heads and apolar tails, respectively. In the context of the valorisation of waste (by-)products (e.g. cheese whey permeate (CWP) and oil wastes), the two sugars are obtainable by enzymatic hydrolysis of lactose, the main component of cheese whey permeate. To overcome the strikingly different solubilities of the two main components, the sugars were converted into isomeric mixtures of α-/β-alkyl glycosides by Fischer glycosylation with naturally occurring alcohols, prior to esterification in molten fatty acid. Cheap, safe and recyclable catalysts were employed in both steps (Amberlyst® 15 and Novozym® 435 (CalB)) in a highly sustainable and easily scalable system. 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 was evaluated (interfacial tension features, W/O emulsification capability and W/O stability over time) [5]. 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/). [1] a) H. M. El-Laithy et al., Eur. J. Pharm. Biopharm. 2011, 77, 43; b) N.S. Neta et al., Crit. Rev. Food Sci. Nutr. 2015, 55, 595. [2] https://www.biosurfproject.it/ [3] N. R. Khan et al., Process Biochem. 2015, 50, 1793-1806. [4] 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. [5] a) S. Sangiorgio et al., Colloids Interface Sci. Commun. 2022, 48, 100630; b) R. Semproli et al., ChemPlusChem. 2023, 88, e202200331.