Liquid-liquid and liquid-solid separation in self-assembled chitosan-alginate and chitosan-pectin complexes

Area of Science:

• Biopolymer science
• Materials science
• Physical chemistry

Background:

• Polyelectrolyte complexation drives liquid-liquid (complex coacervates, CC) or liquid-solid (solid precipitates, SP) phase separations.
• Chitosan (QL), alginate (SA), and pectin (Pec) are widely used polysaccharides in biotechnology.

Purpose of the Study:

• Investigate the impact of pH and ionic strength on chitosan-alginate and chitosan-pectin complexation.
• Characterize the phase behavior and structural transitions of these polyelectrolyte systems.

Main Methods:

• Systematic variation of pH (2-11) and ionic strength (0.05-1.0 M KCl).
• Monitoring of turbidity and structural analysis to identify phase transitions (CC and SP).
• Evaluation of polyelectrolyte properties like ionization degree and molecular characteristics.

Main Results:

• pH and ionic strength significantly influence polyelectrolyte ionization, interactions, and phase behavior.
• Simultaneous CC and SP observed across a range of pH values, with maximum turbidity at pH 5.8.
• QL-Pec favored CC at pH 4.0, while QL-SA maintained both CC and SP structures.
• High ionic strength (1.0 M) reduced QL-Pec interactions via charge screening.

Conclusions:

• Complex coacervates and solid precipitates coexist in both QL-SA and QL-Pec systems.
• Phase transitions are tunable by intrinsic (molecular weight, ionizable groups) and environmental conditions (pH, ionic strength).
• This modulation expands the functional properties and applications of complexed polysaccharides.