Immobilization of a novel cold active esterase onto Fe3O4∼cellulose nano-composite enhances catalytic properties

A novel esterase, EstH was cloned, purified and characterized from the marine bacterium Zunongwangia sp. The purified EstH showed optimum activity at 30 °C and pH 8.5 with ∼50% of original activity at 0 °C. EstH was stable in high salt conditions (0-4.5 M NaCl). To improve the characteristics and explore the possibilities for application, a new immobilization matrix, Fe3O4∼cellulose nano-composite, was prepared and was characterized by Fourier Transform Infrared Spectroscopy (FTIR) and Scanning Electron Microscope (SEM). Interestingly the optimal temperature of immobilized EstH elevated to 35 °C. Compared to its free form, immobilized EstH showed better temperature stability (48.5% compared to 22.40% at 50 °C after 30 min), prolonged half-life (32 h compared to 18 h), higher storage stability (∼71% activity compared to ∼40% after 50 days of storage), improved pH tolerance (∼73% activity at pH 4 and 10), and, more importantly, reusability (∼50% activity after 8 repetitive cycles of usage). Enzyme kinetics showed an increase in the Vmax (from 35.76 to 51.14 μM/min) and Kcat (from 365 s−1 to 520 s−1) after immobilization. The superior catalytic properties of immobilized EstH suggest its great potential in biotechnology and industrial processes.