Cloning, expression, purification and characterization of a thermo- and surfactant-stable protease from Thermomonospora curvata

Abstract

Protease is widely used in various industrial applications to hydrolyze the peptide bonds in protein molecules. The appropriate biochemical characteristics of the proteases for the industry, especially thermostability of the enzyme, are the key requirement for the potential applications. Therefore, we identified, expressed, purified and characterized the recombinant protease from thermophilic bacteria, Thermomonospora curvata (Tcsp). We identified the putative gene of serine protease from the genome of T. curvata. Tcsp which without signal peptide was expressed and purified from E. coli as a soluble form. Here, we report that Tcsp worked efficiently at 70 °C and pH 10. The Km for azocasein was 0.94 mg/ml, and Vmax was 605.04 unit/mg. We also show the thermal stability of Tcsp after heat treatment at various temperatures indicating that Tcsp is a thermostable protease. To elucidate whether Tcsp is still active after the pre-incubation with surfactants at high temperature, Tcsp was pre-incubated in the presence of nonionic, cationic, anionic and amphionic surfactants at high temperature to give insight into the applications in the detergent industry. Tcsp shows significant residual activity after the pre-incubation with surfactants at high temperature, especially after the pre-incubation with nonionic surfactants. The key point of this study is that the first protease gene from T. curvata was intracellularly expressed in E. coli and the protease was purified with time-saving strategies. The potential biochemical characteristics of Tcsp are shown for future industrial applications.