Lipases are a group of water-soluble enzymes that catalyze the hydrolysis (and synthesis) of ester bonds in insoluble acylglycerols at lipid-water interfaces. Lipases hydrolyze triacylglycerides into diacylglycerides, monoacylglycerides, free fatty acids and glycerols. Lipase reaction occurs at the interface between the aqueous and the oil phases because of an opposite polarity between the enzyme (hydrophilic) and their substrates (lipophilic).
Lipases are ubiquitous in nature, that is, they are found in plants, animals and microorganisms. Lipases from microbial sources are of considerable commercial importance because of their high versatility and stability; moreover, they have the advantage of being readily produced in high yields, of which bacterial lipases are more economical and stable. Bacterial lipases are mostly inducible enzymes, requiring some form of oil, fatty acid, fatty acid alcohol or fatty acid ester for their induction. Although there are reported cases of constitutive lipase production by bacteria and they are non-specific in their choice of substrate with a few being thermostable
Such features are responsible for lipases being extensively used for biotechnological applications in the food technology, dairy industry, cosmetics, textile and detergent industries. In the food industry, lipases play a vital role during the fermentative steps of sausage manufacture and to determine changes in long-chain fatty acids liberated during ripening. Lipases remain enzymatically active in organic solvents which enhances their potential and flexibility as biocatalysts against a wide range of unnatural substrates.
Also, they are known to catalyze other reactions like esterification, trans-esterification and inter-esterification between a fatty acid and an alcohol which are the reverse reactions of hydrolysis, making them the most widely used biocatalysts in organic chemistry. In addition to lipases, esterases are also grouped into hydrolases and these two enzymes can often be confused with each other, but they are really different from each other in terms of substrate specificity.
Lipases have been observed to be monomeric proteins, with molecular weight in the range of 19-60 kDa. Generally, bacterial lipases have neutral or alkaline pH value and show activity in a broad pH range (pH 4 to pH 11). The thermal stability of lipases range from 20oC to 60oC. Lipase activity depends on the presence of large surface area and requires mild to extreme conditions, with stability in organic solvents a desirable property in synthetic reactions.
Most known bacterial lipases are stable in organic solvents. The ability of lipases to remain stable in organic solvent without any stabilizer has been found to be in favour of some reactions, highlighting various biotechnological applications of lipases such as the synthesis of chirally important drugs and drug intermediates. Reactions catalyzed by lipases usually occur in organic-aqueous interfaces which is desirable because this ensures the separation of enzyme from substrates or products easily, thus a reduction in cost during downstream processing, which is a highly desired feature in bioprocess engineering.
Adebayo Osesusi is our consultant on industrial biotechnology in MicroBiotics. To get in touch with him, kindly visit our industrial biotechnology page.