Abstract

Many proteases have been isolated and characterized from thermophilic microorganisms with the expectation that these enzymes would have higher intrinsic stability than mesophilic proteases. This expectation is based on the fact that there is a positive correlation between the growth temperature of the microorganisms and its enzyme stability (Cowan et al., 1985). In addition, the properties which allow thermostables enzymes to withstand high temperatures also confer resistance to other factors such as, detergents and denaturing agents, thereby offering great potential advantages for a range of biotechnological processes (Adams et al., 1995). The most detailed studies have been on Thermolysin, a metalloprotease isolated from B. thermoproteolyticus (Endo, 1962). It is the only thermophilic protease currently used on an industrial scale. Recently, the search for more thermostable proteases has been focused on hyperthermophilic archaea. Most of the proteases isolated correspond to intracellular serine enzymes. However, although proteases from hyperthermophiles are certainly more stables, 100°C appears to be the upper limit for long enzyme half lives.