Development of a thermo-stable and recyclable magnetic nanobiocatalyst for bioprocessing of fruit processing residues and D-allulose synthesis.

The aim of the study was to covalently immobilize Smt3-D-psicose 3-epimerase onto functionalized iron oxide magnetic nanoparticles. After immobilization, K of the immobilized enzyme increased, however, V was nearly the same as that of its free form, indicating that immobilization has no detrimental effects on its catalytic output. The covalent immobilization caused a reduction in the deactivation rate constant (k) values leading to 4-5 fold enhancement in its half-life at 50-65°C, indicating significant thermal stability of the iron-enzyme nanobioconjugate. The immobilized enzyme showed excellent storage stability by losing only 20% activity even after 60days of storage at 4°C. The immobilized enzyme retained up to 90% of its initial activity even after 10 consecutive cycles of catalyzing D-fructose epimerization reactions. Thus, after immobilization the enzyme exhibited remarkable improvements in thermal tolerance, storage stability and recycling efficiency, useful for development of industrially exploitable process for D-allulose production.