Enhanced d-hydantoinase activity performance via immobilized cobalt ion affinity membrane and its kinetic study

• IMAM with cobalt ion were used to directly immobilize recombinant DHTase as Co-IDM.
• The Vmax value of Co-IDM is 4.42 times higher than that of free DHTase.
• 98% of the residual activity could be retained for 7 repeated uses.
• Little activity loss was found for a 36-day storage test at 4 °C.
• The Co-IDM gave a markedly enhanced specific activity of 51.89 U/mg.

Various immobilized metal ions affinity membranes (IMAMs) were prepared from the regenerated cellulose membrane (RC membrane) and chelated with various metal ions such as Co2+, Ni2+, Cu2+ and Zn2+. The D-hydantoin-hydrolyzing enzyme (DHTase) harboring a poly-His tagged residue was used as a model protein to be immobilized on the prepared IMAMs through the direct metal–protein interaction forces. The adsorption isotherm and the kinetic parameters Vmax, Km,app of DHTase on IMAMs were studied. The cobalt ions chelated IMAM (Co-IMAM) was found to yield the highest specific activity of DHTase. Under the immobilization condition, the cobalt ion chelated amount was 161.4 ± 4.7 μmol/disk with a DHTase activity of 4.1 ± 0.1 U/disk. As compared to the free DHTase, the immobilized DHTase membrane could achieve a broader pH tolerance and higher thermal stability. In addition, 98% of the residual activity could be retained for 7-times repeated use. Only little activity loss was observed within 36-day storage at 4 °C. This is the first report concerning about using cobalt ion as the effective chelated metal ion for simultaneous purification and immobilization operation.