Engineering and characterization of a novel low temperature active and thermo stable esterase from marine Enterobacter cloacae.

Esterases are one of the most important industrial enzymes. Here, a novel estA was cloned from Enterobacter sp. and characterized. The sequence alignment results showed that it was a novel esterase. The purified EstA had a molecular weight of 26 KDa with an optimum temperature and pH of 40 °C and 9.0. EstA retained >70% activity between 0 °C and 20 °C, indicating it was a low temperature active enzyme. EstA exhibited low activity after incubation at 45 °C for 120 min or 50 °C for 30 min. In the presence of organic solvents, detergents and different concentrations of NaCl, EstA retained high activity. In order to improve thermal stability, a mutant A92D with better thermal stability than EstA was obtained by random mutation. ESTA92D showed high activity at 45 °C for 120 min and maintained 85% of the original activity at 50 °C for 30 min, approximately a 3.4-fold increase over EstA. Homology modeling analysis showed that the improved thermostability of ESTA92D was attributed to hydrophilic Asp rather than hydrophobic Ala, leading to an increase of the interaction and solubility as well as the surrounding area. The improved thermostability of low-temperature-active EstA suggests its immense applications in industrial applications.