Simultaneous purification and immobilization of d-hydantoinase on the immobilized metal affinity membrane via coordination bonds

This study constructs the immobilized metal affinity membrane (IMAM) via coupling of epichlorohydrin, iminodiacetic acid, and nickel ion on the regenerated cellulose membrane. The d-hydantoin-hydrolyzing enzyme (DHTase) harboring a poly-His tagged residue was used as a model protein immobilized on the prepared IMAM. Various immobilization conditions were examined based on the yield of N-carbamoyl-d-p-hydroxyphenylglycine in batch reactions. The immobilization conditions were studied and the optimal conditions are as follows. By employing an IMAM with nickel ion of 155.5 ± 5 μmol/disc immersed in 0.1 M Tris–HCl buffer pH 8 (with 0.8 M sodium chloride) and immobilized time of 14 h, a DHTase activity of 4.2 ± 0.3 U/disc was obtained. The immobilized DHTase membrane can achieve a larger pH and thermal tolerant range than that of free enzyme. Meanwhile, the stability test showed that 99% of enzyme activity could be retained after being repeated 15-times. The storage test also displayed 99% enzyme preservation after 7 weeks of storage.