GENERAL MICROBIOLOGY - T.P. Pyrog - 2004

8. FUNGI

8.7. BIOLOGICALLY ACTIVE SUBSTANCES OF FUNGI

8.7.1. Enzymes

Enzymes are proteinaceous substances capable of catalyzing various Reactions Involving the transformation of matter and energy. They play a critically important role in the vital activity of organisms by mediating METABOLISM, as well as assimilation and dissimilation processes. Furthermore, not only within living organisms but also in a purified state under specific conditions, enzymes catalyze various transformations that are of great significance across numerous fields of Structure/182.html">Practical Application.

Amylases. These are enzymes that hydrolyze starch. Starch consists of amylose (20-30 %) and amylopectin (70-80 %). Amylose is an α-1,4-glucan featuring a linear structure. Amylopectin consists of short (20 residues) chains of α-1,4-glucan, which are interconnected by α-1,6-bonds (branching points).

A complex of starch-degrading enzymes is well known.

α-Amylase hydrolyzes α-1,4-bonds to yield maltose and dextrins. Producers include Aspergillus awamori, Aspergillus niger, Aspergillus amylolyticus, Rhizopus delemar, and others. Purified enzyme preparations have been obtained from these species.

Glucoamylase cleaves individual glucose units from the non-reducing ends of α-1,4-glucoside bonds, producing glucose and occasionally Oligosaccharides. Purified preparations have been obtained from Aspergillus niger, Aspergillus awamori, and Aspergillus oryzae.

α-Glucosidase (maltase) hydrolyzes the disaccharide maltose.

Dextrinase (which breaks down dextrins) has been most thoroughly studied in Fungi of the genera Aspergillus and Rhizopus.

It should be noted that the entire group of amylases has been most extensively studied precisely in these fungi. This is due to the fact that these organisms have long been utilized in practice—for instance, in Japan, for The production of alcoholic beverages and rice- and soy-based products. Amylase is widely used in baking, the production of glucose via enzymatic starch Hydrolysis, medicine, and the textile industry.

Cellulases. These are enzymes that hydrolyze Cellulose. Cellulose is the most abundant organic substance in nature and is a polymer of β-1,4-glucose. The decomposition of cellulose is carried out by a complex of cellulolytic enzymes:

1) exocellulases, which hydrolyze insoluble cellulosic substrates with random Cleavage of β-1,4-bonds within the cellulose molecule;

2) endocellulases, which hydrolyze soluble cellulosic substrates with the cleavage of β-1,4-bonds anywhere along the polymer chain;

3) β-glucosidases and cellobiases, which hydrolyze cellobiose and other β-glucosides;

4) β-glucosyltransferases.

The cellulase of Trichoderma koningii is produced via surface cultivation of the fungus on moistened and acidified wheat bran. The cellulase of Trichoderma viride is produced through submerged cultivation on a medium containing cellulose, glucose, and lactose. To enhance enzyme synthesis, Inducers such as cellulose derivatives are added to the medium.

Active producers of cellulases include Aspergillus terreus, Aspergillus oryzae, Trichothecium roseum, and others.

Cellulases are used in industry to hydrolyze plant raw Materials for Processing aimed at obtaining starch, fats, oils, and other products. They can also be applied in medicine and veterinary science to treat certain forms of dystrophy, and in the food industry to treat rice, grains, and beans in order to accelerate their cooking time.

Xylanases and glucanases. Xylanases hydrolyze xylans (β-1,3- and β-1,4-polymers of xylose). Producers include species of the genus Aspergillus, as well as Fusarium avenaceum. Glucanases hydrolyze glucans and Polysaccharides with mixed bonding types. The β-glucanases of Aspergillus niger, Penicillium funiculosum, and other fungi have been studied in detail.

Pectinases. These enzymes hydrolyze pectic substances (acidic Heteropolysaccharides in which methoxylated galacturonic acid residues are linked by α-1,4-glycosidic bonds). Pectic substances are found in higher plants (berries, fruits, ROOT vegetables). The hydrolysis of pectic substances involves the following enzymes: protopectinase (which converts insoluble protopectin into soluble pectin), pectinesterase (which hydrolyzes the methoxyl groups of soluble pectin), and polygalacturonase (which hydrolyzes the α-1,4-glycosidic bonds of pectic acid down to free galacturonic acids). Pectinases have been studied in Botrytis cinerea, Aspergillus niger, Aspergillus oryzae, Fusarium oxysporum, Rhizopus stolonifer, and others.

Pectinases find their widest application in the production of juices and fruit beverages.

Proteases. These enzymes hydrolyze Proteins and Polypeptides. There are two main groups of Proteolytic Enzymes: proteinases (which catalyze the Breakdown of Proteins into Peptides) and peptidases (which hydrolyze peptides into Amino Acids). Producers of proteases include Representatives of the genera Aspergillus, Mucor, Rhizopus, and Penicillium. Fungal proteases can be acidic (optimal pH 2.5-3.0), neutral, or alkaline (optimal pH 8-11).

Fungal proteases are used to obtain casein hydrolysates, for leather softening, in the baking industry for the production of specialized flour products through the partial hydrolysis of gluten (the flour protein), and in the food industry for tenderizing meat products and processing waste from the meat and fish industries.

Glucose oxidase and catalase. Glucose oxidase catalyzes The oxidation of glucose by molecular oxygen to produce gluconic acid and hydrogen peroxide. The enzyme was obtained from Penicillium vitale. It exhibits antibacterial activity against Gram-positive and Gram-negative Bacteria. The Mechanism of the antibacterial activity of glucose oxidase is due to the action of hydrogen peroxide formed during glucose oxidation. In its native form, the sterile enzyme preparation called "Microcid" is widely used in medicine for the Treatment of purulent infections. Glucose oxidase is also used as a reagent for determining glucose content using the glucose oxidase method (including the determination of Blood glucose levels).