Nickel sulfide nanoparticles incorporated metal organic framework MIL-101(Fe) immobilized with trypsin as an efficient catalyst and proteolytic digestion application

Trypsin has a wide range of industrial and biological applications. In this study, trypsin was immobilized on NiS NPs@MIL-101(Fe) metal–organic frameworks support to overcome problems associated with stability and reusability of the free enzyme. The structural and morphological characteristics of the synthesized material were confirmed using FT-IR, SEM, XRD, BET, and EDX analysis. The enzyme loading and the specific activity at different initial concentrations of trypsin were measured under optimized conditions, and the obtained results were compared. The proteolytic digestion of bovine serum albumin (BSA) was investigated to assess catalytic efficiency. Experimental parameters, including immobilization time, reusability, and pH, were also optimized. The study revealed that the highest loading efficiency of the material was 77% over a broad pH range. The presence of pores in MOF improved the process of immobilization of the enzyme trypsin. The initial activity of the enzyme was preserved for up to 68% after 30 days. Compared with a free enzyme, the immobilized enzyme displayed good stability and maintained 53% of its initial activity after being reused. The enzyme immobilization on NiS NPs@MIL-101(Fe) MOF support significantly enhances BSA proteolytic activity. The catalytic efficiency of trypsin MIL-101(Fe) MOF per unit mass of material was higher than that of MIL-101(Fe) MOF alone for BSA digestion. The proposed material possesses good proteolytic activity and may be applied in industrial and biotechnological fields.