Enzymes find use as functional ingredients in detergents and contribute to cleaning of laundry and dishes in an efficient, environmentally mild, and energy-saving manner. Proteases, lipases, amylases are the major class of detergent enzymes, each provides specific benefits for application in laundry and automatic dishwashing. Proteases are the first to be used extensively in laundry detergents, which not only raise the level of cleaning, but also provide environmental benefits. Lipases and amylases are joined proteases in improving detergent efficacy, especially for household laundering at lower temperatures and, in industrial cleaning operations, at lower pH levels. Cellulases contribute to overall fabric care by rejuvenating or maintaining the new appearance of washed garments.
Detergent mechanism based on enzymes
From an enzyme point of view, detergents on the international market contain principal ingredients that operate by almost identical detergency mechanisms. Soil and stains are removed by mechanical action assisted by surfactants, builders, and enzymes. Alkaline proteases, amylases, or lipases in heavyduty detergents hydrolyze and solubilize substrate soil attached to fabrics or hard surfaces. Cellulases clean by hydrolysis of glycosidic bonds which removes particulate soils attached to cotton microfibers. Key effects of cellulases are to soften and improve the color brightness of worn textile surfaces. Surfactants lower the surface tension at interfaces and enhance the repulsive force between the original soil, enzymatically degraded soil, and the fabric. Builders act to chelate, precipitate or ion-exchange calcium and magnesium salts, to provide alkalinity, to prevent soil redeposition, to provide buffering capacity, and to inhibit corrosion.
Proteases
Proteases are the most widely used enzymes. In laundry detergents, protein stains such as grass, blood, egg, and human sweat are removed through proteolysis. In ADD, proteases secure the removal of proteinaceous food films, which are a particular problem with glassware and cutlery. Serine proteases are the most important group for detergent applications. Proteases catalyze the hydrolytic cleavage of the peptide chain. The most important parameters for the hydrolysis reaction are surface-available substrate S, E/S, pH, reaction time, and temperature. Together with the specificity and properties of the enzyme itself, these parameters are responsible for the course of reaction on a given protein stain.
Amylases
Native starch is only slowly degraded by α-amylases. Gelatinization and swelling are needed to make the starch susceptible to enzymatic breakdown. For most foods, various degrees of gelatinization result from cooking. Therefore, in detergents for laundry and automatic dishwashing, amylases facilitate the removal of starch-containing stains, e.g., pasta, potato, gravy, chocolate, and baby food. Amylases also prevent swollen starch from adhering to the surface of laundry and dishes that may otherwise act as a glue for particulate soiling. Complexes or reaction products between protein, starch, and/or fat are usually found in prepared foods. In such cases, enzyme synergy effects make it possible to remove soil even more efficiently than with single enzyme systems.
Cellulases
Cellulases cleave β-1,4-glucosidic bonds in cellulose and operate directly on the natural cotton fibers or cotton/flax blends and on the cellulose portion in synthetic fibers. Cellulases are applied in detergents to make cotton fabrics regain and maintain clear colors, a smooth surface, and softness. Cellulases provide these effects by shaving off the fuzz and pills of cotton fibrils that are generated on the fabric by normal wear and washing. Cellulases are unique in providing these effects.
Lipases
Because of their strong hydrophobicity, fats and oils are difficult to remove from laundry at low temperatures. Lipases hydrolyze triglyceride to more hydrophilic mono- and diglycerides, free fatty acids, and glycerol. These hydrolysis products are all soluble in alkaline conditions. In laundering, the effects of lipases are seen only after several wash cycles.
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