Coacervation-assisted self-assembly of short-chain glucans for the fabrication of hierarchically porous starch microparticles

Here, we present a simple, sustainable, and efficient strategy for synthesizing porous starch microspheres (PSMP) with hierarchical porosity. This approach exploits the directed self-assembly of debranched waxy maize starch, specifically short-chain glucans (SCGs), facilitated by the existence of chitosan. The debranching enzyme, pullulanase, plays an integral role in initiating coacervation with chitosan through electrostatic interactions beyond its primary function in starch hydrolysis, thereby creating nucleation sites for SCG assembly. The coacervation process undergoes sequential phases of structural transformation and eventual dissipation, culminating in the creation of a highly porous starch framework. The hierarchical porosity of the resulting starch microparticles is further optimized, enabling precise control over their structural and functional properties. Specifically, the Brunauer–Emmett–Teller (BET) surface area was significantly enhanced from 1.68 to 19.63 m²/g, and the total pore volume increased from 0.005 to 0.15 cm³/g (p < 0.01 for both). In addition, the PSMPs exhibited an 82 % higher dye adsorption capacity (from 108 to 198 mg/g) and maintained a high resistant starch content (~70 %) after in vitro digestion. By utilizing enzyme-driven coacervation as an integrated step, this approach fundamentally simplifies the fabrication process while enabling the production of highly functional, eco-friendly porous materials.