Lipases (triacylglycerol ester hydrolases, EC 3.1.1.3) are ubiquitous enzymes that catalyze the breakdown of fats and oils with subsequent release of free fatty acids, diacylglycerols, monoglycerols and glycerol. Besides this, they are also efficient in various reactions such as esterification, transesterification and aminolysis in organic solvents. Therefore, those enzymes are nowadays extensively studied for their potential industrial applications. Examples in the literature are numerous concerning their use in different fields such as resolution of racemic mixtures, synthesis of new surfactants and pharmaceuticals, oils and fats bioconversion and detergency applications. However, the drawbacks of the extensive use of lipases (and biocatalysts in general) compared to classical chemical catalysts can be found in the relatively low stability of enzyme in their native state as well as their prohibitive cost. Consequently, there is a great interest in methods trying to develop competitive biocatalysts for industrial applications by improvement of their catalytic properties such as activity, stability (pH or temperature range) or recycling capacity. Such improvement can be carried out by chemical, physical or genetical modifications of the native enzyme. The present review will survey the different procedures that have been developed to enhance the properties of lipases. It will first focus on the physical modifications of the biocatalysts by adsorption on a carrier material, entrapment or microencapsulation. Chemical modifications and methods such as modification of amino acids residues, covalent coupling to a water-insoluble material, or formation of cross-linked lipase matrix, will also be reviewed. Finally, new and promising methods of lipases modifications by genetic engineering will be discussed.

Customizing lipases for biocatalysis: a survey of chemical, physical and molecular biological approaches

Bioreactors with immobilized lipases: state of the art.

Applications of lipase-catalyzed reactions, such as hydrolysis of fats for the production of fatty acids and esterification or interesterification of fats and other lipids for the preparation of diverse products in food and non-food industries, are reviewed. At present, the application of lipases in biotechnological processes seems to be economically feasible and appropriate mainly for the preparation of specific products of high commercial value, which cannot be prepared conveniently by chemical synthesis. For example, polyunsaturated fatty acids that can be used in dietetic products are prepared under mild conditions by hydrolysis of marine oils and certain plant oils with non-specific triacylglycerol lipases. Very long chain monounsaturated fatty acids (gadoleic, erucic and nervonic) that are of value in oleochemical industry can be prepared by partial hydrolysis of cruciferous oils with sn-1,3-specific lipases. Lipase-catalyzed esterification yields a variety of products, such as monoacylglycerols tha...

Lipase-Catalyzed Reactions for Modification of fats and other Lipids

An enzymatic transesterification method for preparing a margarine oil having both low trans- acid and low intermediate chain fatty acid content is disclosed. The method includes the steps of providing a transesterification reaction mixture containing a stearic acid source material and an edible liquid vegetable oil, transesterifying the stearic acid source material and the vegetable oil using a 1-, 3-positionally specific lipase, and then finally hydrogenating the fatty acid mixture to provide a recycle stearic acid source material for a recyclic reaction with the vegetable oil. Also described is a counter-current method for preparing a transesterified oil. The method includes the steps of providing a transesterification reaction zone containing a 1-, 3-positionally specific lipase, introducing a vegetable oil into the transesterification zone, introducing a stearic acid source material, conducting a supercritical gas or subcritical liquified gas counter-current fluid, carrying out a transesterification reaction of the triglyceride stream with the stearic acid or stearic acid monoester stream in the reaction zone, withdrawing a transesterified triglyceride margarine oil stream, withdrawing a counter-current fluid phase, hydrogenating the transesterified stearic acid or stearic acid monoester to provide a hydrogenated recycle stearic acid source material, and introducing the hydrogenated recycle stearic acid source material into the reaction zone.

Enzymatic method for preparing transesterified oils

Lipases are enzymes that usually hydrolyze acylglycerols, but will hydrolyze the carboxylic esters in many other compounds. They also catalyze esteriftcations and transesterifications. In addition to specificity for carboxylic esters, the lipases are selective for lipid classes and show selectivity for primary vs. secondary alcohols (positional or regio-), fatty acids, enantiomers (chirality of either the acid or alcohol residue) and combinations of these. Uses of the enzymes have depended to some extent on regio- and fatty acid selectivities. Newer applications, such as ester synthesis and asymmetric hydrolysis, may not be based on selectivities. Factors affecting selectivities are discussed and some areas for research are mentioned.

Selectivity is an Important Characteristic of Lipases (Acylglycerol Hydrolases)

Linolenic acid, the component responsible for flavour instability of soybean oil could be reduced to 3% or less by interesterification (acidolysis) of the oil using lipases as catalysts at 10°C.

Selective removal of linolenic acid from soybean oil by lipase-catalyzed interesterification at low temperature

Chemical modification by reductive alkylation of porcine pancreatic lipase with n-butyraldehyde, isobutyraldehyde and acetone resulted in about 50% increase in theVmax of the enzyme.Eact was reduced by about 40% by this modification. Both hydrolytic and interesterification activities were enhanced without affecting the 1,3-specificity of the enzyme.

M. Saroja

Papers

Selective removal of linolenic acid from soybean oil by lipase-catalyzed interesterification at low temperature

Enhancement of catalytic activity of porcine pancreatic lipase by reductive alkylation