Enzyme are biocatalyst involved in cellular metabolic functions and control the rate of reaction by lowering the activation energy of the reaction. Enzymes produced by marine microbes (bacteria) are important in biotechnology due to their range of unusual properties. Some are salt resistant, a characteristic that is often advantageous in industrial processes (detergents and industrial cleaning application). Marine enzymes are used to study the ion channels (like saxitoxin and tetrodotoxin as Na+ -channel blockers, brevitoxins Na+ channel activators, biosensors for detecting environmental pollution, pathogen detection and disease diagnostic in aquaculture. Marine enzymes have also been applied in preparation of organic fertilizer, pollution control like waste water treatment, degradation of plastic, degradation of toxic pollutants e.g. phenol and its methylated derivatives, aromatic hydrocarbon and alkanes and bioremediation of fossil fuels.
LIPASES AS AN IMPORTANT ENZYME
The demand for industrial enzymes, particularly of microbial origin, is ever increasing owing to their applications in a wide variety of processes. Enzyme-mediated reactions are attractive alternatives to tedious and expensive chemical methods. Enzymes find great use in a large number of fields such as food, dairy, pharmaceutical, detergent, textile, and cosmetic industries.
It is in the last decade that lipases have gained importance to a certain extent over proteases and amylases, especially in the area of organic synthesis. The enantioselective and regioselective nature of lipases have been utilized for the resolution of chiral drugs, fat modification, synthesis of cocoa butter substituents, biofuels, and for synthesis of personal care products and flavour enhancers. Thus, lipases are today the enzymes of choice for organic chemists, pharmacists, biophysicists, biochemical and process engineers, biotechnologists, microbiologists and biochemists.
Lipases (triacylglycerol acylhydrolases) belong to the class of serine hydrolases and therefore do not require any cofactor. The natural substrates of lipases are triacylglycerols, having very low solubility in water. Under natural conditions, they catalyse the hydrolysis of ester bonds at the interface between an insoluble substrate phase and the aqueous phase in which the enzyme is dissolved under certain experimental conditions, such as in the absence of water, they are capable of reversing the reaction. The reverse reaction leads to esterification and formation of glycerides from fatty acids and glycerol. The occurrence of the lipase reaction at an interface between the substrate and the aqueous phase causes difficulties in the assay and kinetic analysis of the reaction. The usual industrial lipases are special classes of esterase enzymes that act on fats and oils, and hydrolyse them initially into the substituted glycerides and fatty acids, and finally on total hydrolysis into glycerol and fatty acids
A relatively smaller number of bacterial lipases have been well studied compared to plant and fungal lipases. Bacterial lipases are glycol-proteins, but some extracellular bacterial lipases are lipoproteins reported that enzyme production in most of the bacteria is affected by certain polysaccharides. Most of the bacterial lipases reported so far are constitutive and are nonspecific in their substrate specificity, and a few bacterial lipases are thermo stable in nature.
In the present day industry, lipases have made their potential realized owing to their involvement in various industrial reactions either in aqueous or organic systems, depending on their specificity.
Lipases in Food and dairy industry
Lipases are used extensively in the dairy industry for the hydrolysis of milk fat. Current applications include flavour enhancement of cheese, acceleration of cheese ripening, manufacture of cheese-like products, and lipolysis of butter fat, and cream. While the addition of lipases primarily releases short-chain (C4 and C6) fatty acid that leads to the development of sharp, tangy flavour, the release of medium-chain (C12 and C14) fatty acids tends to impart a soapy taste to the product. In addition, the free fatty acids take part in simple chemical reactions where they initiate the synthesis of other flavour ingredients such as aceto-acetate, ß-keto acids, methyl ketones, flavour esters, and lactones.
Lipases in detergents
The usage of enzymes in washing powders still remains the single biggest market for industrial enzymes. The world-wide trend towards lower laundering temperatures has led to much higher demand for household detergent formulations.
Lipases in oleo-chemical industries
The scope for application of lipases in the oleochemical industry is enormous as it saves energy and minimizes thermal degradation during hydrolysis, glycerolysis, and alcoholysis. The current trend in the oleochemical industry is a movement away from using organic solvents and emulsifiers. The various reactions involving hydrolysis, alcoholysis, and glycerolysis have been carried out directly on mixed substrates, using a range of immobilized lipase. This has resulted in high productivity as well as in the continuous running of the processes. Enzymatic hydrolysis perhaps offers the greatest hope to successful fat splitting without substantial investment in expensive equipment as well as in expenditure of large amounts of thermal energy.
Lipases in synthesis of triglycerides
The commercial value of fats depends on the fatty acid composition within their structure. A typical example of a high-value asymmetric triglyceride mixture is cocoa butter. Acidolysis, catalysed by 1, 3-specific lipases, is used in the preparation of nutritionally important products which generally contain medium-chain fatty acids. Lipases are being investigated extensively with regard to the modification of oils rich in high-value polyunsaturated fatty acids such as Arachidonic acid, Eicosapentaenoic acid, and Ducosahexanoic acids. Substantial enrichment in the polyunsaturated fatty acid content of mono-glyceride fraction has been achieved by lipase-catalysed alcoholysis or hydrolysis.
Lipases in synthesis of surfactants
Polyglycerol and carbohydrate fatty acid esters are widely used as industrial detergents and as emulsifiers in a great variety of food formulations (low-fat spreads, sauces, ice-creams, mayonnaises). Enzymatic synthesis of functionally similar surfactants has been carried out at moderate temperature (60-80°C) with excellent regioselectivity. Lipase from A. terreus synthesizes a biosurfactant by transesterification between natural oils and sugar alcohols. Lipases may also replace phospholipases in the production of lysophospholipids. Lipases may also be useful in the synthesis of a whole range of amphoteric bio-degradable surfactants, namely amino acid-based esters and amides.
Lipases in pharmaceuticals and agrochemicals
The utility of lipases in the preparation of chiral synthons is well recognized and documented. Technology has been commercialized to produce 2(R),3(S)-methylmethoxyphenyl glycidate, the key intermediate in the manufacture of the optically pure cardiovascular drug Diltiazem.
Lipases have applications as industrial catalysts for the resolution of racemic alcohols in the preparation of some prostaglandins, steroids, and carbocyclic nucleoside analogues. Regioselective modification of polyfunctional organic compounds is yet another rapidly expanding area of lipase application, particularly in the field of AIDS treatment.
Lipases in polymer synthesis
The stereoselectivity of lipase is useful for synthesis of optically active polymers. These polymers are asymmetric reagents, and are used as absorbents. In the field of liquid crystals, suitable monomers can be prepared by lipase-catalysed transesterification of alcohols, which with racemic alcohols may be accompanied by resolution. The use of chiral glycidyltosylates for the preparation of ferroelectric liquid crystals has also been reported. Thus, this enzyme has diversified commercial use, both in terms of scale and processes. Furthermore, this enzyme has potentials in newer fields, for example lipases have successfully been used in paper manufacturing - apparently, the treatment of pulp with lipase leads to a higher quality product and reduced cleaning requirement. Similarly, the enzyme has also been used in association with a microbial cocktail for the treatment of fat-rich effluents from an ice-cream plant. This could also be utilized in waste processing of many food industries.
BETTER LIPASE SOURCE AND PROPERTY ENHANCEMENT
Among all classes of lipases, People are more focusing on lipases in extreme conditions and cold active lipases and alkaline lipases are important enzyme source from marine microbes. Cold active lipases from marine microbes have been used as additives in laundry detergent. Also cold adopted microbes and their enzymes have been used as catalysts for organic synthesis of unstable compounds at low temperatures. Cold adopted enzymes could also be developed as agents for bioremediation at low temperatures. Alkaline lipases have equal contribution towards benefit of human society. It is used to solve various environmental issues like oil spills in water sources, reclamation of acid soil by addition of CaCO3 into the soil and alkali resistant microbes, and increasing fertility of acid soil by applying alkaline chemicals with these important enzymes and synthesis of organic chemicals. So research have been focused on metabolic engineering of the these extreme lipases for its better use.
About Author / Additional Info:
The author is now working in Department of biotechnology, IIT-Kharagpur. His broad area of research is Microbiology of contaminated aquifers.