Getting the most out of cheese whey: An integrated biotechnological platform for the synthesis of bio-based surfactants

Cheese whey (CW) is the main waste stream of dairy industry accounting for ~200 million tons worldwide with ~40 million tons being produced in the European Union. [1] After protein recovery, the resulting cheese whey permeate (CWP) contains mainly lactose, thus providing a pool of carbohydrates (lactose, glucose and galactose) that can be upcycled for the synthesis of fine and commodity chemicals In this project, an integrated bioprocess was set-up for the synthesis of Sugar Fatty Acid Esters (SFAE) which are valuable non-ionic surfactants. [2] CWP was used both as the feedstock for enzymatic biotransformations and for growing oleaginous yeasts to produce the galactose-based “head” and the lipid “tail” of SFAE, respectively (Figure). As a proof-of-concept, 1-butyl β-D-galactopyranoside was synthesized by reacting commercial lactose (1 mmol) with 1-BuOH through a transglycosylation reaction catalyzed by the covalently immobilized β-galactosidase from Aspergillus oryzae in a ternary system composed of alcohol/acetone/McIlvane buffer pH 4.3 (50/30/20). Subsequently, 1-butyl β-D-galactopyranoside was submitted to the esterification step with commercial palmitic acid in a solvent-free system at 80 °C by using Novozym 435 as the biocatalyst, affording pure n-butyl 6-O-palmitoyl-β-D-galactopyranoside. Interfacial features and emulsifying properties of the synthesized SFAE were evaluated. This sugar ester showed promising interfacial features and was able to stabilize water-in-oil emulsions up to 48 h. [3] At this point, we moved to the use of the crude CWP as substrate. On the one hand, CWP was submitted directly to the transglycosylation reaction in 1-BuOH, giving 1-butyl β-D-galactopyranoside in a yield comparable to that of the reference process (40%). On the other hand, microbial lipids were produced by growing oleaginous yeasts on CWP and mango syrup obtaining cells with a 45% lipid content. Microbial lipids were extracted and their composition both in terms of lipid species and fatty acid profile was assessed by GC-MS. Triglycerides are the most abundant lipids (77%) containing almost 50% saturated fatty acids (palmitic and stearic acids) and mostly oleic acid as the unsaturated component. [4] The esterification of 1-butyl β-D-galactopyranoside with the microbial lipids is currently in progress. Acknowledgements This work was financially supported by Cariplo Foundation (Italy) (call: “Circular Economy for a sustainable future 2020”, project BioSurf, ID 2020-1094). 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. [1] F.J. Barba, Foods 2021, 10, 564. [2] B. Pérez, S. Anankanbil, Z. Guo, in Fatty Acids: Chemistry, Synthesis and Applications, 2017, Chp. 10, 329-354. [3] R. Semproli, M.S. Robescu, S. Sangiorgio, E. Pargoletti, T. Bavaro, M. Rabuffetti, G. Cappelletti, G. Speranza, D. Ubiali, ChemPlusChem 2023, 88, e202200331. [4] S. Donzella, A. Fumagalli, S. Arioli, L. Pellegrino, P. D’Incecco, F. Molinari, G. Speranza, D. Ubiali, M.S. Robescu, C. Compagno, Fermentation 2022, 8, 341.