Dextran-Mediated Macromolecular Crowding Drives the Formation of Multiphase Complex Coacervates from Soy Glycinin and Gum Arabic

Macromolecular crowders pose great impact on coacervation but that on the protein–polysaccharide complex coacervation has yet been investigated. In this study, dextran (Dex) was used as a crowder to investigate its influence on the complex coacervation of soy glycinin (SG) and gum arabic (GA). Due to the excluded volume effect of Dex, coacervate yield significantly increased. Intriguingly, under the crowded environment, multiphase coacervates occurred which was dependent on both the Dex concentration and pH. In multiphase coacervates, SG was concentrated in the inner phase while GA was evenly distributed and Dex was mostly excluded. Fluorescence recovery after photo bleaching showed that the outer phase which was originated from the dilute phase upon adding Dex was significantly more fluid than the inner phase. This contributed to the improved redispersibility of the multiphase coacervates. Collision experiments using optical tweezers showed a faster coalescence rate and shorter relaxation time for multiphase coacervates. The multiphase structure formation appeared to be correlated with the pH-dependent dissociation of SG, suggesting a possible role of different oligomeric species in phase partitioning. This study will advance the physicochemical understanding of protein–polysaccharide coacervation and enable the design of coacervates with tunable internal architecture. Such multiphase coacervates can be further exploited to fabricate multilayered microcapsule structure and hold promise as membraneless organelles for artificial cell construction.