Physicochemical Properties of Thermoreversible Glucan Aggregates Synthesized by Amylosucrase from <i>Deinococcus geothermalis</i>

Developing tunable temperature-responsive carriers for hydrophobic bioactives remains challenging. Amylosucrase (ASase, E.C. 2.4.1.4) efficiently catalyzes the synthesis of α-1,4-glucans using sucrose as the sole substrate. This study synthesized thermoreversible soluble short-chain glucan aggregates (tsSCGAs) at varying sucrose concentrations (100-900 mM) and investigated their physicochemical properties. Notably, sucrose concentration effectively controlled both structure and functionality: higher concentrations decreased the number-average degree of polymerization and molecular weight, favoring shorter glucan chain formation. Morphological analyses revealed that tsSCGAs synthesized at 100 and 300 mM formed small spherical particles with B-type crystallinity, whereas those at 500-900 mM formed larger amorphous microparticles. Thermoreversible solubility behavior was observed in tsSCGAs synthesized at 100-500 mM, with differential scanning calorimetry showing distinct endothermic and exothermic transitions. β-Carotene was successfully encapsulated within tsSCGAs, confirmed via Raman spectroscopy. These tunable properties enable tsSCGAs to serve as novel temperature-responsive carriers, offering controlled release of hydrophobic bioactives.