Enzymes bleach-resistant

The industrial use of rDNA technology includes the production of bleach-resistant enzymes that are used in laundry detergents to degrade... 

Genencor International, Inc. received a patent for a process to make bleach-resistant protease enzymes to use in detergents. 

Some examples of hydrolases are listed in Table 7.3 according to the industrial sector in which they are used. Most of these hydrolases operate in the hydrolytic mode, since only a few processes are currently known that make use of the synthetic power of hydrolases. Increasingly, however, these enzymes are being tailored by genetic tools such as random or site-directed mutagenesis and overexpression to lower the operational costs of the biocatalyst and to obtain enzymes of high purity, as well as to meet specific customer requirements such as stability, substrate specificity, and optimal pH and temperature of operation. A typical example is the protease subtilisin from Bacillus subtilus, which was made bleach-resistant by replacing one bleach-sensitive amino acid (cysteine) by the chemically inert alanine [12]. 

Genetic engineering led to creating bleach-stable enzymes by replacing the sensitive methionine with an oxidation-resistant amino acid (discussed in Sec. IV.B). 

In contrast to cellulose, which is crystalline, strong, and resistant to hydrolysis, hemicellulose has a random, amorphous structure with little strength. It is easily hydrolyzed by dilute acid or base, but nature provides an arsenal of hemicellulase enzymes for its hydrolysis. Hemicellulases are commercially important because they open the structure of wood for easier bleaching and thus support the introduction of ECF or TCF methods. Many different pentoses are usually present in hemicellulose. Xylose, however, is always the predominating sugar. The pentoses are also present in rings (not shown) that can be five- or six-membered. 

Previously, we determined that the only known mode of action that is selective for grasses/monocots is acetyl CoA carboxylase inhibition.6 This enzyme is the first of two enzymes involved in de novo fatty acid biosynthesis. This mode of action prevents the synthesis of many essential wax compounds. In order to screen our compounds for this mode of action, we used resistant oat (Avena sp.) seeds. The emodin analogues caused dose-dependent bleaching (Fig. 1.7) and a severe decrease in germination for both resistant and nonresistant grasses. 

Enzymes have improved over the years so that food stains on clothes, and unmentionable stains on undergarments, now present no problem. In the late 1980s, enzymes were engineered that could resist the action of the peroxide bleach and by 2000 it was possible to have a mix of all kinds of enzymes in the same detergent. Because enzymes are themselves protein molecules, a protease enzyme could in theory attack other enzymes and digest them as well, so special varieties have been developed to overcome this. Today, enzyme demand is... 

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