Valorization of dairy waste stream : chemoenzymatic synthesis of bio-based emulsifiers

Sugar fatty acid esters (SFAEs) are a class of non-ionic surfactants characterized by excellent interfacial tension reduction capability, low toxicity, and biodegradability. These properties make SFAEs extremely promising for cosmetic and food applications as emulsifiers, alongside to the fact that they can be obtained from renewable sources, thus answering the need for evermore sustainable and circular chemistry.1 Herein, cheese whey permeate (CWP), the main waste stream of dairy industry, was used as starting material to produce bio-based surfactants. Specifically, CWP was enzymatically hydrolysed into a mixture of glucose and galactose which was then submitted to a two-step chemoenzymatic synthetic protocol.2 The first step (Fischer glycosylation) was not straightforward since several parameter influenced both yield and isomeric ratio. Therefore, the reaction conditions were optimized by means of a chemometric study. In the second step an enzymatic esterification reaction was conducted to obtain an isomeric mixture of n-butyl 6-O-palmitoyl-D-glycosides and its surfactancy was deeply investigated in terms of static/dynamic interfacial tension and water-in-sunflower oil (W/O) emulsion stabilization capacity over time. Computational studies were conducted on isolated couples of anomers, namely pyranosides- and furanosides-based compounds, to study the role of the ring size on the final emulsifying properties of the isomeric mixture.