Biochemical Engineering Fundamentals Part 1 - Bailey J., Ollis D. 1989

Applications of Enzyme-Catalyzed Reactions
Applications of Hydrolytic Enzymes
Enzyme Mixtures, Pectic Enzymes, and Other Applications of Enzymes

Instead of individual Enzymes, it is often more convenient or practical to use their mixtures. The Components of the mixture may belong to the same type (a- and ß-amylases or Trypsin and Chymotrypsin) or to different enzyme classes (such as pancreatic extracts, which are a mixture of trypsin, lipase, and amylase). For instance, using specific mixtures of various amylases can increase the yield of saccharified starch, which serves as a raw material for alcohol production via Alcoholic Fermentation, whereas an amylase mixture with a lower ß-amylase content, which reduces the viscosity of starch solutions without significant saccharification, is more appropriately used, for example, in textile desizing. Animal pancreatic extracts contain a mixture of digestive enzymes capable of performing many Functions of the human pancreatic juice enzyme complex. At least one preparation produced in the USA on an industrial scale as a detergent additive contains a mixture of bacterial proteases and amylases; this preparation has been reported to be more effective than proteases alone in removing certain types of stains.

Oxidation of galactose to galacturonic acid followed by polycondensation leads to The formation of polygalacturonic acids. The latter are the main structural element of A number of natural Materials of plant origin called Pectins. In pectins, carboxyl groups are often esterified to carbomethoxyl groups. The enzyme pectin methylesterase (pectinesterase, hydrolyzing pectase) hydrolyzes carbomethoxyl groups, while polygalacturonases (pectinases, pectolases) cleave glycosidic bonds in pectins. Fruits serve as the Main sources of the first type of enzymes, whereas the second type is obtained mainly from Fungi.

Pectic enzymes are most widely used in two sectors of the food industry: juice production and winemaking. Primary Processing of fruits and vegetables yields highly viscous juices, which is perfectly acceptable for tomato and citrus juices but often undesirable for apple and other juices. Through controlled partial Hydrolysis of pectins, it is possible to obtain a product with the required fluidity, yet sufficiently viscous to prevent the precipitation of insoluble solids. In apple juice production, more extensive pectin hydrolysis is applied, which facilitates subsequent filtration to ensure the desired clarity of the juice. If the juices are intended for use in The production of jellied products, they are treated only with pectinesterase. The resulting polygalacturonic acids are then gelled using Calcium Ions.

Another important area of application for pectic enzymes is winemaking. Adding a mixture of pectic enzymes to crushed grapes increases juice yield, enhances the extraction of coloring matter from the skins, and accelerates filtration and pressing processes. Treatment of already fermented grape juice with pectic enzymes also yields positive results, accelerating the Separation of wine from Yeast and sediment, and improving its clarity and stability (primarily by reducing the concentration of suspended Proteins in the finished wine). Thus, in both areas of application, pectic enzymes primarily help achieve the desired viscosity and filterability of intermediates, which has a positive impact on process economics and the appearance of the finished product.

Class="center">Table 4.6. Promising or developing Applications of Hydrolases

In the future, pectic enzymes may also find application in the treatment of softwood. Freshly felled wood of such species, for example Norway spruce, is resistant to impregnation with chemical preservatives. As it turns out, pretreatment with pectic enzymes improves wood permeability, thereby increasing the efficiency of chemical impregnation.

Other hydrolytic enzymes are also used on a limited scale; furthermore, promising new processes utilizing hydrolases are currently under development (Table 4.6).