Enzyme preparations are widely used in food, and this article will detail the roles of different enzyme preparations in food.
Esterases:
Esterases facilitate the hydrolysis of esters into acid and alcohol in aqueous solution. They differ from lipases in that they primarily hydrolyze short-chain acylglycerols rather than long-chain ones. Esterases are widely used in the food and alcoholic beverage industries to modify oil and fat in fruit juices and produce fragrances and flavors. Feruloyl esterases, an important group of esterase enzymes, break the ester bond between ferulic acid and different polysaccharides in plant cell walls. They are also essential for waste management due to their ability to hydrolyze lignocellulosic biomass. Cheng and colleagues identified a protease-resistant feruloyl esterase that can release ferulic acid from wheat straw, which has commercial potential due to its pH and thermal stability. In cheese production, the fruity flavors are derived from different methyl or ethyl esters of short-chain fatty acids, and bacterial production of these esters has been reported. Feruloyl esterase is also crucial in the biosynthesis of ferulic acid, the precursor for vanillin, an aroma compound commonly used in food and beverages. Microbial production of feruloyl esterase has been reported by several researchers.
Cellulases:
Cellulases are enzymes that break down polymeric cellulose by hydrolyzing β-1,4 linkages to release glucose units. There are three major classes of cellulases: endo-(1,4)-β-d-glucanase, exo-(1,4)-β-d-glucanase, and β-glucosidases. Cellulases belong to the glycosyde hydrolase (GH) family and use acid-base catalysis to cleave glycoside bonds in cellulose. Endoglucanases cleave β-1,4-bonds in the amorphous region of cellulose, while exoglucanases act on reducing or non-reducing ends of the cellulose polymer to liberate cellobiose. β-Glucosidases catalyze the final step in cellulose breakdown by cleaving non-reducing terminal β-d-glucosyl residues and removing β-d-glucose.
Cellulases are produced by a large diversity of microorganisms during their growth on cellulosic materials. They are mainly sourced from bacteria and fungi, and are widely used in various industries such as textile, paper, detergent, and food production. Cellulases are utilized in the juice industry to improve the extraction methods, clarification, and stabilization of juices, as well as to reduce the viscosity of nectar and puree from fruits such as apricot, mango, plum, papaya, pear, and peach. They are also used for the extraction of flavonoids from flowers and seeds, and for the extraction of phenolic compounds from grape pomace. β-Glucosidases, in combination with pectinase, alter the structure, flavor, and aroma of fruits and vegetables, and are reported to reduce bitterness of citrus fruit while improving aroma and taste. Cellulases are also used in combination with other enzymes for efficient olive oil and wine extraction, where they improve maceration, color development, must clarification, and overall wine stability and quality.
Lipoxygenases:
Lipoxygenases, or LOX, are enzymes involved in the dioxygenation of polyunsaturated fatty acids in lipids that contain a cis-1,4-pentadiene. They consist of a single polypeptide chain that is further assembled into an N-terminal domain and a catalytic β-barrel domain. LOX enzymes are non-heme iron-containing enzymes. The LOX-catalyzed reaction produces different precursors for the production of various volatile and aroma-producing chemical substances in plants. LOXs are used in the food industry for aroma generation and in bread making. The most studied lipoxygenase enzyme is soya bean LOX. Bacterial LOXs exhibit different specificities towards fatty acids. LOX from Nostoc sp. oxygenates at a specific site in linoleic acid, but the LOX from Anabaena sp. exhibits variable specificity.
LOXs are mainly applied in dough due to their ability to bleach the flour pigment carotenoid by co-oxidation of the pigment with fatty acids. Lipoxygenases are also employed to improve dough’s tolerance to mixing and different handling properties. This effect is due to the oxidation of the thiol group in gluten, which may lead to the redistribution of different disulphide bonds, tyrosine cross-linking, and subsequent strengthening of the gluten. This also leads to an improvement in dough rheology. Recently, Patel et al. purified lipoxygenase from Lasiodiplodia theobromae by different chromatography techniques and fully characterized the enzyme.
Xylanases:
Xylanases are enzymes produced by microorganisms to break down xylans, a major component of hemicellulose. There are three main types of xylanases – endoxylanases, exoxylanases, and β-xylosidases – which work together to break down the xylan backbone in hemicellulose. Endoxylanases cleave the β-1,4 bonds of the xylan backbone, exoxylanases hydrolyse β-1,4 bonds from the non-reducing ends to release xylooligosaccharides, and β-xylosidases cleave xylobiose and xylooligosaccharides to release xylose. Xylanases typically contain a catalytic module for performing their major functions and some may also have a carbohydrate binding module for binding to substrates. The two major catalytic modules of hemicellulases are glycoside hydrolases and carbohydrate esterases.
Xylanases are produced by microbes such as actinomycetes, bacteria, and fungi. Streptomyces sp., Bacillus sp., and Pseudomonas sp. are major actinomycete and bacterial species producing xylanase, while Aspergillus sp., Fusarium sp., and Penicillium sp. are major fungal species producing xylanase. Fungal xylanases have higher activity than bacteria or yeast. The pH range for effective xylanase activity is broader in bacteria and actinomycetes (pH 5.0-9.0), while fungi have high content and extracellular release of the enzyme.
Xylanases are widely used in the bread making industry along with other enzymes to improve the rheological properties of dough through enzymatic hydrolysis of non-starch polysaccharides. Xylanase increases the specific bread volume, improves the quality of bread, and delays crumb formation. Xylanase is also used in biscuit production to improve texture, tastiness, and palatability. In the juice production industry, xylanase improves extraction, clarification, and stabilization when used in combination with other enzymes. Xylanase is also used in beer making to hydrolyse the cellular wall of barley, which reduces the muddy appearance and viscosity of the beer by releasing arabinoxylans and lower oligosaccharides.
Pectinases:
Pectinases are enzymes that break down glycosidic bonds in pectic polymers. These enzymes can be categorized into polygalacturonases, pectin esterases, pectin lyase, and pectate lyase, and can be produced from natural or recombinant microbes. Pectinases can act on smooth or hairy regions of pectin and can be classified as acidic or alkaline, endopectinases or exopectinases based on pH and mode of action.
Pectinases have various industrial applications such as in paper bleaching, food industry, and remediation. Addition of pectinase to juices results in clearer appearance and better filterability compared to enzyme-depleted counterparts. Pectinases can also reduce turbidity and haze generation in naturally derived fruit juices, and improve their color and flavor. The use of biogenic enzymes such as pectinases in juice production can be almost nine times more effective than mechanical maceration in removing haze and increasing viscosity.
Glucose oxidase:
Glucose oxidase is an oxidoreductase enzyme (EC 1.1.3.4) belonging to a large family of enzymes. It was discovered in 1928 by Müller and is a flavoprotein that can convert glucose to gluconic acid in the presence of dissolved oxygen. The enzyme catalyzes the oxidation of β-d-glucose to gluconolactone and the reduction of molecular oxygen to hydrogen peroxide. Gluconolactone is then hydrolyzed to gluconic acid. The enzyme is homodimeric, consisting of two similar polypeptide chains that are covalently linked by disulfide bonds and each contains one non-covalently bound flavin adenine dinucleotide (FAD) molecule at the active site region. Glucose oxidase can be produced by various microorganisms, but Aspergillus niger and Penicillium glaucum are commonly used for its production.
Glucose oxidase has a wide range of industrial applications in pharmaceuticals, food, and biofuel cells. Its use in the baking industry is increasing because of its oxidizing effects that make dough stronger. In the food industry, it enhances the flavor, aroma, and stability of food products by removing glucose and oxygen from diabetic drinks and egg white. Glucose oxidase improves the color, texture, flavor, and shelf life of food products and prevents them from rotting. It is also used in food packaging to increase storage life by removing oxygen.
Laccases:
Laccases are a group of oxidases that belong to the largest subgroup of multicopper enzymes. They are commonly known as blue oxidases and are used to study their potential to oxidize phenolic compounds. These enzymes have a wide range of applications in various industrial sectors, including chemical synthesis, biobleaching of paper pulp, bioremediation, biosensing, wine stabilization, and textile finishing. The specificity of laccases for substrates depends on the type of microbial source producing the enzyme.
Laccases catalyze the oxidation of a wide range of compounds, such as phenolics, aromatic amines, and ascorbate. The mechanism of catalytic activity of laccase is described in various reports. Laccases are secreted extracellularly by several fungi as a product of their secondary metabolism during fermentation, but their production is limited to a few fungal species. Well-known producers of laccases belong to Deuteromycetes, Ascomycetes, and Basidiomycetes.
Laccase is used in various industrial applications, including the modification of the color appearance of food and beverage industries and wine stabilization. It is also used in the cork stopper manufacturing industry. Laccases have been applied to avoid haze formation in the brewing industry, and they are used for oxygen removal in the final step of beer production to prolong the storage life of beer. Additionally, laccase is used in baking to enhance the stability, strength, and machinability of bread batter.