The Identification and Partial Characterization of a Novel Inducible Extracellular Thermostable Esterase from the Archaeon Sulfolobus shibatae

Extracellular esterases have so far only been reported in eubacteria, here we report the first identification and partial characterisation of a novel inducible extracellular esterase from the thermoacidophilic archaeon Sulfolobus shibatae. This esterase exhibits remarkable stability to both acid and heat. Esterase activity is induced by growth on a range of polyoxyethylenesorbitan (Tween) compounds as sole carbon source. Activity occurs over a wide temperature (25-99°C) and pH (pH4.0-9.0) range and is optimal at 90°C and pH6.0. It exhibits high thermal stability, with a half-life of 20 min at 120°C, and shows a transient thermal activation of 60% at 90°C. The thermal inactivation of function occurs by first order kinetics, and after 120 min incubation at 120°C 50% of activity still remains, It is able to hydrolyse mono- and diglycerides, but is unable to hydrolyse the triglycerides olive oil and triolein, which is indicative of an esterase and not a lipase.