Stability of Industrial Enzymes

Abstract

Abstract Industrial enzymes are nowadays widely used in a great variety of applications. An important property of an industrial enzyme is its stability, defined as its ability to retain activity under various conditions. This stability aspect relates to the entire life cycle of the enzyme which comprises production (fermentation, downstream processing and formulation), distribution (transport and storage) and the final application. In general, more stable enzymes can be obtained in several ways: screening for more stable ones (thermophiles, extremophiles), chemical modification, protein engineering, immobilization or by using stabilising additives. For industrial enzymes, the use of additives and protein engineering have found wide application. Altough the latter technique is relatively young, already a few mutant enzymes have entered the market for industrial enzymes. We have been able by using protein engineering to improve the stability of several industrial enzymes. The storage stability of a detergent protease (Maxacal ® ) in bleach containing high duty powder detergents was improved considerably by mutating a methionine in the active site (position 216). A few oxidation stable mutants revealed the same specific wash performance as the wild type enzyme which made these therefore suitable as second generation product. The operational half life of immobilized glucose isomerase (Maxazyme GI-immob ® ) could be increased 2–3 fold by mutating a lysine in the subunit interface (position 253) into an arginine. This mutation is supposed to prevent the enzyme from dissocation after glycation of the said lysine by glucose which is present in the process. The specific activity of the mutant Lys253Arg was the same as that for the wild type enzyme. Random mutagenesis yielded thermostable mutants of α-amylase from Bacillus licheniformis (Maxamyl ® ), used in the liquefaction of starch. Since no 3D-structure of the enzyme is available, the effect of the observed mutations (e.g. His133Tyr) could not be rationalized. Also in this case, the specific activity of the mutant was the same as for wild type enzyme.