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 (0-4.5M 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 30min), prolonged half-life (32h compared to 18h), higher storage stability (∼71% activity compared to ∼40% after 50days 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 51.14μM/min) and Kcat (from 365s(-1) to 520s(-1)) after immobilization. The superior catalytic properties of immobilized EstH suggest its great potential in biotechnology and industrial processes.