Directly covalent immobilization of Candida antarctica lipase B on oxidized aspen powder by introducing poly‑lysines: An economical approach to improve enzyme performance.

In our previous study, we could achieve high soluble expression of Candida antarctica lipase B (CalB) in E. coli by fusion poly‑amino acid tags on CalB (pCalB). Herein, we are surprised to find that pCalB can be easily and directly covalent binding on a simply oxidized aspen powder (OAP) by the aid of poly‑lysine tags. Under the optimal conditions, 72.9 ± 3.6% of the total protein could be immobilized, and the activity recovery of immobilized pCalB (pCalB-OAP) was 98.9 ± 3.8%. The analysis of scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR) indicated that OAP was a suitable carrier for enzyme immobilization. The immobilized pCalB-OAP could exhibit excellent thermal stabilities, and it retained a residual activity of 58.4 ± 2.8% at 55 °C, whereas only 21.2 ± 2.2% of its initial activity for free pCalB was observed. And it could also display a nice tolerance for the changes of pH environment, compared with that of free pCalB. The results that pCalB-OAP could retained 73.6 ± 2.9% of their initial activity in (R, S)-NEMPAME hydrolysis after the tenth cycles, suggested that pCalB-OAP could be effectively recycled. The immobilization strategies established here were simple and inexpensive.