Study of the interactions between trypsin and soybean lecithin as a basis for developing antibiofilm microcapsules

This study is part of a project that aims to develop antimicrobial microcapsules containing emulsions stabilized by soy lecithin (SL) and a proteolytic enzyme, trypsin. The formation of complexes obtained from the interactions between SL and trypsin at different SL/trypsin ratios (0-0.8) at pH 3.5 was studied. The results showed that small-sized soluble complexes (about 10 μm) formed at SL/trypsin ratios below 0.12, while larger-sized insoluble complexes emerged at ratios between 0.12 and 0.25. As the SL/trypsin ratio increased further, the complexes dissociated. These results were confirmed by particle size distribution, zeta potential, and turbidity analysis. Fluorescence quenching and isothermal titration calorimetry demonstrated that the interactions between trypsin and low concentrations of SL were a spontaneous exothermic reaction driven by entropy and were mainly electrostatic, which shifted toward hydrophobic interactions as SL concentration increased. Molecular docking validated the dominance of hydrophobic and electrostatic interactions, with contribution of hydrogen bonding. This study provides valuable insights into the SL-trypsin complexation mechanism, laying the groundwork for designing stable antibacterial and antibiofilm microcapsules for food, medical, and biotechnology applications.