CHARACTERISTICS OF A NEW LIPASE FROM A Thermus sp BACTERIUM

Abstract

Thirty strains of the genus Thermus, isolated from hot sprins in Portugal, were screened for the secrection of lipases. In the end, the strain LFF1 received our attention for further characterization. We report here some kinetic properties of the crude extracellular extract when used in a reversed micellar system of AOT in isooctane for the hydrolysis of triolein. In common with other lipases, this extract showed maxima at pH 7 and temperatures in the range 40-50 °C, but significant residual activities were also observed at higher (up to 80 °C) and lower (downto -3.5 °C) temperatures. The hydrolysis oftriolein in the micellar system followed an apparent Michaelis- Menten kinetic mechanism with K,,(app)=7.1%(v/v) and V_.„(app)=55.5 mole/(ml.h.mg protein). The specific activity of the extract decreased continuously with increasing concentrations of protein encapsulated in the reversed micelles. The aqueousextract lost less than 9% of its activity when stored at 4 °C for almost 3 months.