Enzyme immobilization with plant-based polysaccharides through complex coacervation

Plant-based polysaccharides (PSs) were used to immobilize phytase in a coacervate system. Molecular docking predicted the intermolecular interactions and conformations between the phytase and the polysaccharide and correlated them to the activity recovery of phytase in the coacervate complex. PSs with two different functional groups, sulfate (iota (IC), lambda (LC), and kappa (KC) carrageenan) and carboxylate (low methoxyl pectin (LMP) and sodium alginate (SA)) were investigated. The optimized conditions for coacervation and activity recovery were pH 4 with a phytase-to-polysaccharide volume ratio of 12:1. Zeta potential measurements, FTIR spectroscopy, and molecular docking confirmed that electrostatic interactions and hydrogen bonding were the main driving forces for coacervate formation. Coacervate complexes of phytase formed with LMP, SA, or KC showed a high activity retention after immobilization, with approximately 30% yield of complex and 75% immobilization efficiency of the phytase. The lower enzyme activity retention observed for IC and LC complexes is attributed to these PSs binding to the enzyme's active site. Overall, this work contributes to the body of knowledge about intermolecular interactions between phytase and polysaccharides and can serve as a guide to formulating stable, functional ingredients for a plant-based diet.