Evaluation of Immobilisation Matrices for Phytase: Evaluation of Ionotropically Gelled Matrices

Phytase immobilisation offers significant potential advantages for enhancing enzyme stability, reusability, and applicability in food and beverage systems. However, the choice of carrier materials and immobilisation strategy critically influences catalytic performance, particularly when substrate interactions or matrix components inhibit activity. Various immobilisation systems for phytase were evaluated with the aim of maintaining catalytic efficiency while minimising adverse interactions with phytic acid. Initial approaches employed chitosan-tripolyphosphate (TPP) and chitosan-iron crosslinked beads. Calcium alginate systems were also investigated as a mild entrapment technique. To overcome observed limitations, κ-carrageenan beads were developed using potassium-ion-induced gelation. Immobilisation yield and efficiency, as well as catalytic activity were assessed across all systems. Chitosan-based systems demonstrated good structural stability but suffered from electrostatic interactions with phytic acid and metal-substrate complexation, negatively affecting enzyme activity. Calcium alginate systems reduced these effects but still exhibited residual Calcium induced phytate complexation, limiting substrate accessibility and decreasing specific activity to 9 – 10 PPU/mg enzyme, compared to 73 PPU/mg for the calcium-free enzyme. In contrast, κ-carrageenan beads showed improved performance. The system achieved an immobilisation efficiency of 42 %, particularly at lower enzyme loading (0.05 mg/mL). Furthermore, κ-carrageenan enabled linear and sustained phosphate release over hydrolysis time without evidence of saturation or substrate-product diffusion limitations. The absence of interfering ions such as calcium and iron contributed to improved catalytic behaviour. Therefore, κ-carrageenan presented as a promising immobilisation matrix for phytase, enabling sustained catalytic activity while avoiding inhibitory interactions observed in other systems. This approach supports efficient phytic acid degradation and has strong potential for application in food and beverage processing.