FROM DAIRY WASTE TO BIO-BASED SURFACTANTS: ENZYMATIC SYNTHESIS OF n-BUTYL 6-O-ACYL-GALACTOSIDES

Cheese whey permeate (CWP), a lactose-rich aqueous byproduct of dairy industry, can be exploited as feedstock for the synthesis of fine and commodity chemicals. In the BioSurf project, an integrated bioprocess was set-up for the synthesis of Sugar Fatty Acid Esters (SFAE), valuable non-ionic surfactants.[1] CWP was used both for enzymatic biotransformations and for growing oleaginous yeasts to produce the galactose-based “head” and the lipid “tail” of SFAE, respectively. Upon the proof-of-concept with commercial lactose,[1] CWP was used to synthesize 1-butyl β-D-galactopyranoside (1) through a transglycosylation reaction catalyzed by the immobilized β-galactosidase from Aspergillus oryzae in a ternary system (buffer/1-BuOH/acetone) at 30 °C (yield: 45%). At the same time, microbial lipids were produced by growing oleaginous yeasts on CWP (cell lipid content: 45%).[2] Microbial lipids were submitted to acid-catalyzed extraction and in situ transesterification giving fatty acid ethyl esters (FAEE, 2a-e, yield: 80%). 1-Butyl β-D-galactopyranoside (1) and FAEE (2a-e) were reacted by a solvent-free transesterification catalyzed by the immobilized lipase from Thermomyces lanuginosus affording a mixture of n-butyl 6-O-acyl-galactosides (3a-e, yield: 40%). The products, characterized by NMR, will be tested for their surfactant properties.