SUSTAINABLE PRODUCTION AND PHYSICO-CHEMICAL CHARACTERIZATION OF BIOSURFACTANTS FROM RENEWABLE RESOURCES

Cheese whey permeate (CWP) represents the main waste stream of the dairy industry. To produce 10 kg of cheese, around 100 kg of milk are used and roughly 90 kg of cheese whey (CW) are generated as a by-product. CW is still considered a valuable source of milk proteins, which are recovered by ultrafiltration, thus resulting in around 89 kg of CWP, but it contains a high concentration of lactose (up to 45-50 g/L). In the frame of applying a bio-based circular economy approach, this study aims at exploring the use of lactose and its hydrolysis products, glucose and galactose, as cheap and abundant substrates to produce value-added products, like sugar fatty acid esters (SFAEs). SFAEs are non-ionic surfactants that are characterized by excellent surface and interfacial tension reduction capability, low toxicity, and biodegradability. Moreover, the components of SFAEs can derive from natural resources, thus allowing the final product to be labeled as natural and bio-based as well. These features make them extremely promising for industrial applications as emulsifiers in the cosmetic and food sectors. Some SFAEs are currently produced at industrial level and they are available on the market (i.e. sorbitan and ethoxylated sorbitan esters, Span® and Tween®, as well as sucrose esters and alkyl polyglycosides). However, their current synthesis still rely on acid homogeneous catalysis and harsh reaction conditions, which result, in most cases, in complex mixtures of products with different degrees of esterification and different acylation positions, as well as mixtures of undesired by-products, deriving from side reactions, such as sugar dehydration/caramelization. In this thesis, alternative and more sustainable approaches have been described. In particular, enzymatic esterification, acetalization or Fischer glycosylation followed by solvent-free esterification, were investigated as sustainable alternatives to the currently established chemical schemes for the preparation of a small library of performant SFAEs, by exploring the use of challenging substrates, i.e., lactose and CWP. Moreover, the physico-chemical properties, such as interfacial tension features, W/O emulsification capability and the relative stability over time, of the prepared biosurfactants were evaluated to assess their potential application as bio-emulsifiers in the food, pharmaceutical and cosmetic industries.