Interactions between Soybean Trypsin Inhibitor and Chitosan in an Aqueous Solution

Area of Science:

• Biopolymer interactions
• Supramolecular chemistry
• Food science

Background:

• Protein-polysaccharide complexes offer potential for encapsulating bioactive compounds.
• Understanding these interactions is crucial for developing stable colloid-based products.
• Soybean trypsin inhibitor (STI) and chitosan (CS) are key biopolymers with potential applications.

Purpose of the Study:

• To investigate the interaction between STI and CS in aqueous solutions.
• To determine the influence of pH and CS concentration on complex formation.
• To evaluate the protective effect of STI-CS complexes on STI stability.

Main Methods:

• Analysis of state diagrams, turbidity, and zeta potential.
• Spectroscopic techniques (CD spectra) to assess structural changes.
• Microstructural analysis and simulated gastric digestion experiments.

Main Results:

• STI and CS form soluble/insoluble complexes via hydrophobic (pH 4.0) or electrostatic (pH 6.0) interactions.
• STI secondary structure remained largely unchanged with same-charge CS, slightly altered with opposite-charge CS.
• STI-CS complexes demonstrated a protective effect on STI during simulated gastric digestion.

Conclusions:

• Chitosan concentration and pH significantly affect STI-CS complex formation and properties.
• Non-covalently bonded STI-CS complexes enhance protein stability.
• These findings provide a theoretical basis for using CS-STI supramolecular structures as carrier substances.