High-efficient and reversible capture of protein by oxidized and carboxymethylated starch nanocrystals: Understanding interaction mechanism and regulating complexation

Layer-by-layer assembly systems for functional proteins and polypeptides are gaining interest in food nutrition due to their health benefits. However, understanding the interactions between core-template materials and proteins remains challenging. This study investigated the complexation between oxidized and carboxymethylated starch nanocrystals (OSNC and CSNC) and lysozyme (LYS). Optimal complexation was achieved at pH 6 without ionic strength, and with a higher degree of modification. At LYS concentrations of 0.5 mg/mg and 0.25 mg/mg, OSNC and CSNC achieved maximum binding capacities of 0.417 mg/mg and 0.178 mg/mg, respectively. Micromorphologies showed LYS was primarily bound to the nano-lamellar surface of OSNC and CSNC. Although electrostatic interactions were predominant, hydrophobic interactions also contributed to CSNC-LYS complexation. LYS was nearly fully released (0.419 mg/mg for OSNC-LYS and 0.178 mg/mg for CSNC-LYS) with minimal impact on its structure and bioactivity. These findings provide a foundation for stabilizing proteins and polypeptides in functional foods.