Lipases enzymes catalyze the hydrolysis and synthesis of esters formed from long-chain fatty acids and glycerol. They are widely distributed in the plant world, bacteria, molds as well as in milk products and in animal tissues, especially in the pancreas. They have applications mainly in dairy, oleochemical, pharmaceuticals, paper & pulp, cosmetics, textile, detergents and leather industries. It is one of the most reported groups of enzymes for the production of biofuels.
Lipases are found in wide diversity of sources such as blood, gastric juices, adipose tissues, intestinal juices and pancreatic secretion. Lipases are subclass of esterases that catalyzes the formation, cleavage (hydrolysis), digestion and transport of fats (lipids). If lipase is produced in sufficient quantity it can use fat stores to be burned as fuel. In eukaryotes, lipases are involved in various stages of lipid metabolism including absorption, lipoprotein metabolism, fat digestion and reconstitution. In plants, lipases are present in energy reserve tissues. Lipases are produced by higher eukaryotes as well as many microorganisms. Microbial lipases are most useful for industries. Some lipase-producing microorganisms are bacteria, yeast, fungi and actinomycetes. Some of the lipolytic bacterial species are Bacillus subtilis, Pseudomonas fragi, Bacillus megaterium, Staphylococcus aureus, Burkholderia cepacia, Pseudomonas aeruginosa, and pseudomonas pseudoalcaligenes. Some common lipase producing fungal species are Helvina lanuginosa, Rhizopus delemar, Eurotrium herbanorium, Aspergillus niger, Mucor circinelloi and Penicillium citrinum etc.
Physical & Chemical Properties of Lipases
Structurally Lipase enzyme is a monomeric protein and has a molecular weight of 19-60 kDa. It’s activity generally depends on the availability of large surface area, requires extremely mild conditions and is pH dependent. Lipases are generally stable at or near a neutral pH, but some may be stable up to pH 4.0 and 8.0. For the expression of its activity cofactors are not essential but divalent cations stimulate the activity. Though the maximum activity of lipase is found in the range of 30-35°C, but it can be stable at lower temperature also.
Functions & Biological Role of Lipase Enzyme
Lipase enzyme has so many biological actions in our body:
- Digestion of Nutrients: One of the most important functions of lipase is digestion of fat. When we consume food, the fats from food pass through the stomach undigested into the small intestine. Pancreas releases the enzyme lipase, which hydrolyzes fats into smaller particles that can pass through the wall of the intestine and into the lymphatic ducts, after that they eventually pass into our bloodstream.
- Cholesterol Transport: Lipase helps our body to package cholesterol to transport in the blood. A specific lipase cholesterol acyltransferase (LCAT) combines fatty acids with cholesterol then the molecules are packaged by the body into transporter particles like LDL and HDL, respectively and moves them to or away from the cells.
Industrial Uses of Lipase Enzyme
Lipases form an integral part of the industries ranging from dairy, food, cosmetics, leather, textile, pharmaceuticals, detergents, tea industries and bioremediation processes. They are also being exploited as versatile and cheap catalysts to degrade lipids in more modern applications. Lipase enzymes are available in market for baking, to be used in detergents and also as biocatalysts in alternative energy production to convert vegetable oil into fuel. Lipases shows promising applications in detergent formulations, organic chemical processing, synthesis of biosurfactants, dairy industry, paper manufacture, the oleochemical industry, the agrochemical industry, cosmetics, pharmaceutical and nutrition processing . The main use of hydrolytic lipases is their use in detergents. About 1000 tons of lipases have been added to 13 billion tons of detergents produced every year. Lipases and Food Industry Lipase enzyme has a diverse role in almost every field of food processing industry some examples are as follows:
Dairy Industry In dairy industries lipases are extensively for the hydrolysis of milk fat. It is used to enhance the flavour of cheeses, in acceleration of cheese ripening, manufacturing of cheese products and lipolysis of cream. Lipases when act on milk fat, generate free fatty acids, which leads to production of many dairy products, particularly cheeses with specific flavour characteristic. Bakery Food In baking industry, there is an increasing focus on lipolytic enzymes. Recent findings suggest that lipases can be used to substitute traditional emulsifiers since the enzymes degrade wheat lipids to produce emulsifying lipids in situ. It was primarily used to improve the flavour content of bakery products by liberating short-chain fatty acids through esterification along with flavour enhancement. Lipase is found in fats and oils which can break a fat down into free fatty acids and glycerol. Lipases are found also in the fat of meat, fish, eggs, milk and cereals. Lipases are being used extensively in the mayonnaise, dressing and whipping to improve its quality and texture. The quality of black tea is dependent largely on the dehydration, enzymatic fermentation and mechanical breaking. While processing black tea, enzymatic breakdown of membrane lipids initiate the formation of volatile products with characteristic flavour properties. Lipases in Fat and Oil Processing Modification of fats and oil are one of the prime areas in food processing industry that demand novel economic and green technologies. Lipases allow us to modify the properties of lipids by altering the location of fatty acid chains in the glyceride and replacing them with other ones.
Use of Lipase in Other Industries
Pulp and Paper Industry
The enzymatic pitch control method using lipases have been used since early 1090s in a large-scale paper-making process as a routine operation since early 1990s. Severe problems in pulp and paper manufacturing are caused by pitch or the hydrophobic components of wood. Lipases are used to separate the pitch from the pulp for paper manufacturing.
Enzymes are used in the laundry detergents for the removal of oil stains from fabrics. It allows detergents to work in lower temperatures and also shorter periods of agitation are needed, often after a preliminary period of soaking. Nowadays, so many detergents contain cocktails of enzymes like amylases, proteases, lipases and cellulases. In general, it removes protein from clothes soiled with blood, grass, sweat, milk etc. far more effectively than non-enzyme detergents. However, use of modern bleaching and brightening agents, the difference between looking clean and being clean may be difficult to discern.
Lipases have potential application in cosmetics and perfume industries because of its use in surfactants and in aroma production. Although the cost of esterification by lipase remains too high for the manufacturing of bulk products yet esters synthesis has found its way in the market place.
The current trend in the oleochemical industry involves the use of immobilized lipases to save energy, minimize thermal degradation during hydrolysis, glycerolysis and alcoholysis by using mixed substrates. Thus it ensures high productivity as well as continuous running of the processes. Enzymatic hydrolysis offers the successful fat splitting without substantial investment in expensive equipment and in expenditure of large amounts of thermal energy.
Lipases in Environmental Management and Bioremediation
Employment of lipases in bioremediation processes is a new aspect in biotechnology. The wastes of lipids in restaurants and processing factories can be cleaned by its help. The strains which produce lipases played a key role in the enzymological remediation of polluted soil. In bioremediation field Cold-adapted lipases shows great potential in fat contaminated cold environment, water waste treatment and active compounds synthesis in cold condition. By the use of lipase oil spills in refinery, shore sand and processing factories can be handled. The enzymes that can active at low and moderate temperature are also ideal for bioremediation process.
Lipases as Diagnostic Tools
Lipases are also important drug targets or marker enzymes in the medical sector. They are used in the enzymatic determination of serum triglycerides to generate glycerol which is determined by enzyme linked colorimetric reactions. Its level in blood serum may be used as a diagnostic tool for detecting acute pancreatitis and pancreatic injury.
Biodiesel is a liquid biofuels; they are esters of long chain fatty acids and short chain alcohols. Transesterification is the central reaction in the biodiesel production which could be catalyzed either enzymatically or chemically. Enzymatic transesterification has advantages over chemical transesterification, as it is less energy intensive, allows easy recovery of glycerol and the transesterification of glycerides with free fatty acid contents. Lipases represent most reported groups of enzymes for production of biofuels.
The large number of hydrolytic applications, like flavor enhancement in dairy products, beverages, milk chocolate etc. it is a promising field of lipase enzyme. Other than the food industry, lipases have been applied in the synthesis of fine chemicals, the production of biopolymeric materials, biodiesel production, detergent industry, organic synthesis, textile industry, paper and pulp industry, the synthesis of ingredients for personal care products, the synthesis of surfactants and of structural triglycerides, agrochemical production, the oleochemical business, the pesticide industry and in environmental management.