The enzymes work by transforming hazardous waste molecules into less toxic ones. This results in less dangerous sludge and makes it easier to pump, process and dewater.
Enzymes are biocatalysts created by microorganisms to cause explicit chemical reactions. They can operate under mild reaction conditions, are able to attack specific pollutants and do not influence other parts of the wastewater.
Oxygenases
Wastewater treatment enzymes help in breaking down and transforming toxic contaminants in the water source. These contaminants can be phenols and dyes, which are harmful to the environment. They can also be proteins, fats, and other chemicals that need to be broken down or transformed to be reused.
Oxygenases are oxidoreductases that bind oxygen to substrates using molecular oxygen and cofactors such as FAD/NADH, flavins, or ferredoxins. They are categorized as dioxygenases and monooxygenases on the basis of the number of oxygen atoms they utilize in the oxidation reaction.
Oxygenases have significant potential as industrially applicable oxidative biocatalysts for diverse chemical transformations including hydroxylation, deacetylation, desaturation, epimerization, and ring-cleavage reactions. For example, 2-oxoglutarate-dependent L-isoleucine dioxygenase (2OGX) enzymes accept free-standing amino acids as substrates and perform a wide range of hydroxylations and dioxygenation reactions. These include hydroxylation of the L-isoleucine into (2S,4S)-5-hydroxyleucine and sulfoxidation of L-methionine.
Peroxidases
Peroxidases are a class of enzymes that catalyze the oxidation of several organic compounds with hydrogen peroxide. They are a group of oxidoreductases with broad substrate specificity, regioselectivity and enantioselectivity. These enzymes are commonly used for treating waste liquids containing dyes, phenols and other toxic materials.
They are produced by plants and other microbes. They are classified as heme or non-heme proteins based on the type of molecule that interacts with peroxide. The heme peroxidases have a hemin-catalytic center, while the non-heme peroxidases have a selenol or reactive thiol.
Heme peroxidases can be found in many plant sources including horseradish (Armoracia rusticana), papaya (Carica papaya), guava (Psidium guajava), banana (Musa paradisiacal) and bare olives (Olea europaea). Other fungi have also been reported to produce non-heme peroxidases such as white rot fungi. These peroxidases have the unique ability to degrade a wide variety of pollutants in wastewater including polychlorinated biphenyls, dioxins, petroleum hydrocarbons and munitions wastes. They convert these chemicals into insoluble molecular pigments which can be easily extracted and disposed of.
Proteases
Proteases break down proteins and their conjugates, such as peptide bonds, into smaller molecules. These small molecules are easily absorbed and metabolized by microbes and plants. They also have the ability to react with other chemicals to form more complex compounds. Microbial proteases are effective in degrading phenolic, aromatic, and inorganic contaminants that are typically difficult to decompose with regular chemical oxidants.
Microbial proteases are able to attack target pollutants with little or no influence on other parts of the wastewater effluent. In addition, they can be used at a specific temperature and pH range, even under gentle reaction conditions.
As a result, they are more useful than regular physicochemical treatment methods. In fact, they have been found to be safer than conventional oxidation techniques. When added to contaminated soils, lagoons, or municipal water supply, these enzymes help break down multiple waste types and restore the water to healthy drinking conditions.
Amylases
A very common use of enzymes is to help break down organic pollutants that are found in the wastewater of a variety of different industries. These enzymes work to degrade these organic pollutants by breaking them down into smaller parts that can be more easily absorbed and metabolized by microbes.
Amylases are an important type of enzyme in a microbial mixture that is used to treat wastewater. They hydrolyse the internal glycosidic bonds in starch molecules to produce maltose and dextrins, which are soluble carbohydrates. This is done by cutting the a1-4 glycosidic bond in starch and forming disaccharides and oligosaccharides.
These are then broken down by the other types of enzymes in a microbiological system. These include polyphenol oxidases, which break down the phenolic pollutants in the wastewater into soluble molecular pigments that are more easily separated and removed from the water. This helps to speed up the degradation process.
Lipases
Lipases are enzymes that cleave the hydrophobic linkages of large organic polymer molecules to simpler monomer units that can be absorbed and metabolised by cells. They are a critical part of biological wastewater treatment and can reduce the dependency on environmentally-harmful chemicals for the degradation of organic compounds in the sewage system.
Microbial lipases are highly effective and non-toxic for the degradation of phenolic pollutants. They break phenolic pollutants into smaller, less toxic molecular pigments that can be extracted and easily disposed of. They are also useful in removing oil and grease from wastewater by breaking the bonds of fats, oils and waxes.
Lipid-rich wastewater discharged by food processing industries and household activities is a major source of secondary pollution. Existing physicochemical treatments for lipid-rich wastewater are expensive and unsustainable, while microbial lipase mediated bioremediation is a promising alternative. However, there are limited studies on the development of microbial lipases suitable for environmental application.
Cellulases
Cellulases have been used for many purposes in a number of industries. Some of them include paper and pulp, laundry detergent, agriculture, medicine, and food and beverages. These enzymes are classified as complex and noncomplex. A complex cellulase consists of multiple proteins with a catalytic domain and a cellulose-binding domain. This enzyme is produced by anaerobic microorganisms and it is known as a “cellulosome.”
Microbial cellsulases can be used in wastewater treatment to reduce biological oxygen demand, reduce the amount of triglycerides in sewage sludge, and extract phenolic compounds such as carotenoid. These enzymes can also be used to improve the sensory properties of fruit and vegetable products.
Microbial cellulases are produced by fungi and bacteria. Thermotoga maritima is one species that produces this enzyme. It consists of two protein b-sheets with an active site in the middle. These enzymes cleave b-1,4-glycosydic bonds in the chain of lignocellulose and facilitate its degradation.