Detergents enzymes

Several new detergent enzymes have emerged on the market (Table 1). Truly alkaline proteases, introduced in 1974 and 1982, were fermented on strains of Bacillus lentus firmus. These enzymes have a pH optimum between 9 and 11, and have taken important market shares from Alcalase. 

In 1989, two enzymes based on genetic engineering techniques were introduced, ie, a cloned alkaline protease (IBIS) and a protein engineered Subtihsin Novo (Genencor, California). Lipase and ceUulase types of detergent enzymes have also begun to appear. 

A given enzyme may be assayed by its action on soluble substrates under chemical and physical conditions different from those encountered in a real-life wash. Such experiments indicate the enzyme s performance with respect to pH and temperature variations, or in conjunction with other soluble substances, etc. The analytical data thus obtained are not necessarily representative of the wash performance of the enzyme, and real wash trials are necessary to evaluate wash performance of detergent enzymes. 

The effectiveness of proteolytic, amylolytic, and lipolytic detergent enzymes is based on enzymatic hydrolysis of peptide, glucosidic, or ester linkages. The mainstay of the market has been the protease types. 

Sarlo, K., et al., Respiratory allergenicity of detergent enzymes in the guinea pig intratracheal test association with sensitization of occupationally exposed individuals, Fundam. Appl. Toxicol., 39, 44, 1997. 

Robinson, M.K., et al., Use of the mouse intranasal test (MINT) to determine the allergenic potency of detergent enzymes comparison to the guinea pig intratracheal (GPIT) test, Toxicol. Set, 43, 39, 1998. 

Detergent enzymes, 10 273—286 cleaning effects of, 10 275 functions of, 10 274—275 performance evaluation of, 10 276—278 Detergent fragrances, 18 362 Detergent industry... 

A. Crutzen and M. Douglass, Detergent Enzymes A Challenge, in G. Broze, (ed.), Handbook of Detergents, Marcel Dekker, New York, 1999. 

As mentioned in part 2.1.3 hydrolytic enzymes are the most frequently used enzymes in organic chemistry. There are several reasons for this. Firstly, they are easy to ttse because they do not need cofactors like the oxidoreductases. Secondly, there are a large amormt of hydrolytic enzymes available because of their industrial interest. For instance detergent enzymes comprise proteases, celltrlases, amylases and lipases. Even if hydrolytic enzymes catalyse a chemically simple reaction, many important featirres of catalysis are still contained such as chemo-, regio- and stereoselectivity and specificity. 

Since the mid-60s, the use of enzymes in detergents has been the largest of all enzyme applications. Over half of all detergents presently available contain enzymes, in particular proteases, amylases, lipases and ceUulases. Besides improved washing efficiency, the use of enzymes allows lower temperatures and shorter wash periods (of agitation) to be employed, often after a preliminary period of soaking. Further in this chapter (section 3.3) the detergent enzymes are worked out in more detail. 

Starch, fats and proteins cause ugly stains in textile. However, imder the influence of the right enzymes these disappear as snow for the sun. Already for decades detergent manufacturers tried to further refine the concept of enzymatic stain removal. Currently enzyme engineers and biotechnologists work together to develop more ideal detergent enzymes. 

Until the end of the sixties enzyme products such as the detergent proteases were just powder products. Today very few powdered-enzyme products remain. All detergent enzyme products from the larger enzyme suppliers arc either hquid formulations or granulated and further protected by coatings. Today formulation techniques really have become a science with MAC-values in production facilities of 10-100 nanogram/m air. It is further recommended that the use of such safe enzyme products shall be planned such that the liquid enzyme product is not spilled and allowed to diy and aerosol formation shall be prevented. With these simple rules in mind, industrial enzymes arc very safe. 

The oxidative stability of subtilisin has been extensively studied and improved stability has been engineered. In subtilisin BPN two methionines, MET " and MET are especially susceptible to oxidation. To prevent the negative influenee eaused by the formation of methioiune sulfoxide the MET can be substituted with ALA, SER or LEU, without loosing more than 12-53% of the activity. One such mutant MET222. ALA is currently in use as a commercial detergent enzyme Durazyme (Riisgard, 1990). 

In many applications several quite different technical criteria must be successfully fulfilled before the product will work , and even then cost and scale-up and commercial criteria must be met. A good example is detergent enzymes where scientists had to discover proteases that would be active and stable under conditions of high pH and temperature and in the presence of oxidising and surface active agents. The same criteria exists for lipases for use in detergents. However, suitable lipases proved rather more difficult to find than the B. subtilis proteases that are used... 

Detergent enzyme performance is often reported in the form of such dose-response curves. The performance increases dramatically at the beginning, but reaches a maximum levd at higher enzyme concentrations. The extent to which the enzyme is able to remove stains from the fabric depends on the detergent system, temperature, pH, washing time, wash load, etc. Enzyme wash performance varies between liquid and powder detergents and with the composition of the soiling (Fig. 6). 

The stimulatory effect of nonionic detergents on the sialyltransferase reactions may reflect an interaction of the hydrophobic environments of the active sites with the detergents, possibly by the insertion of the latter into the lipid bilayer surrounding the enzymes or by the formation of detergent-enzyme complexes, thus inducing more active enzyme conformations (51,52,53). The effect of nonionic detergents may be similar to the previously reported effects of phosphatidyl ethanolamine (34), CDP-choline and lysolecithin (54,55), phospho-diglycerol and cardiolipid (56). 

Enzymes used in laundary detergents are almost all produced using Bacillus enzymes, most commonly Bacillus subtilis or Bacillus licheniformis, which all secrete the detergent enzymes into the fermentation broth. The market is highly concentrated two producers cover more than 50% of the market share worldwide Novozymes (Bagsvaerd, Denmark) and Genencor (Palto Alto/CA, USA). Table 6.2. lists several commercial products with their functions. 

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