Food waste valorization using palmified UiO-66 as support for Cyclodextrin glycosyltransferase in cyclodextrin...

For economic and effective enzymatic conversion of abundant starch-containing food waste into cyclodextrin, the development of efficient and stable immobilization support is essential. In this study, UiO-66, a water-stable zirconium-based metal-organic framework (MOFs), was surface-modified using sodium palmitate and employed as a support for CGTase immobilization to convert waste rice into cyclodextrin. The modification aimed to introduce hydrophobicity to the UiO-66 surface, thereby improving conformational structure of the enzyme and enhancing its interaction with the support. Adsorption studies revealed that the modified UiO-66 exhibited approximately 50% higher maximum protein uptake compared to the parent UiO-66, and the adsorption behavior well described by the Langmuir adsorption model. The optimum temperature of the immobilized biocatalyst was 90 °C, higher than the 70 °C observed for the free CGTase, showing improved thermal stability after immobilization. Furthermore, UiO-66-palmitate showed superior catalytic activity in converting untreated waste rice into cyclodextrin in a continuous packed-bed reactor system. Reusability studies revealed that the immobilized biocatalyst retained nearly 75% of its initial activity after repeated use. Overall, this study highlights the potential of surface-modified UiO-66 as a robust biocatalyst for converting food waste into cyclodextrin, and demonstrates a sustainable pathway for valorizing starch-rich waste streams, supporting the circular bioeconomy initiatives adopted by many nations.