Biosynthesis of pectic oligosaccharide-based amphiphiles as novel stabilizers of nanoemulsions by coupling enzymatic depolymerization with alkyl/alkenyl succinylation

Abstract

Pectic oligosaccharides (POS) are gaining increasing recognition as a novel kind of prebiotics. Here, a new multipurpose amphiphilic POS was synthesized by coupling pectinase-mediated depolymerization of citrus pectin with lipase-catalyzed alkyl succinylation. Structural characterization by thin-layer chromatography, size exclusion chromatography, mass spectrometry, Fourier transform infrared spectroscopy, 1H nuclear magnetic resonance, and transmission electron microscopy showed that POS obtained by enzymatic hydrolysis consisted mainly of octamers and hexamers and was subsequently hydrophobically functionalized by reaction with alkylsuccinic anhydrides of various alkyl chain lengths to develop amphiphilic properties. Emulsions stabilized by pectin and alkylsuccinylated POS were assessed by analysis of droplet size distribution, zeta potential, and confocal fluorescence microscopy. The results showed that POS-derived amphiphiles POS-SA12 and POS-SA22 (alkyl C12 and C22) formed stable nanoemulsions with mean particle size of <200 nm and a narrow polydispersity index of <0.20, compared to pectin-based microemulsions (>1100 nm in size and >0.8 polydispersity index). Differences were largely ascribed to the well-balanced hydrophobicity of the introduced alkyl group and the hydrophilicity of the carboxyl groups in the molecular structure of POS-SA12. Our study introduces a green synthetic approach for the production of a novel POS-derived amphiphile with prebiotic and emulsifying properties showing excellent performance in stabilizing oil/water emulsions and other extensive applications.