The interaction between Lactobacillus exopolysaccharide and soy protein during the fermentation process: Aggregation characteristics and binding kinetics.

In order to elucidate the molecular mechanism of the interaction between the exopolysaccharides (EPS) of Lactobacillus casei (CEPS) and soy protein isolate (SPI) during fermentation, an acidified CEPS-SPI composite systems were constructed to analyze the aggregation characteristics and binding kinetics. The results indicated that the interaction between CEPS and SPI was regulated by both CEPS concentration and pH. CEPS increased the pH at which soluble complex formation begins (pHφ1), decreased the pH at which maximum soluble complex formation occurs (pHmax). The minimum solubility and the zero value of the zeta potential shifted towards lower pH. During acidification, the forces between the complexes change dynamically and are divided into three phases: the early phase (pH 7.0-6.5, van der Waals forces and hydrogen bonding), the intermediate phase (pH 6.5-5.5, hydrophobic and electrostatic interactions), and the late phase (pH 5.0-4.5, electrostatic interactions). This study provided a theoretical basis for EPS to regulate the functional properties of proteins during fermentation and offered valuable theoretical support for developing high-end fermented soy products.