Higher tolerance of a novel lipase from Aspergillus flavus to the presence of free fatty acids at lipid/water interface

The main objective of this work was to identify novel lipases of industrial interest. In this paper, Aspergillus flavus lipase (AFL) was isolated from the traditional tannery of Fez city in Morocco; it kept its stability even in the presence of high concentrations of detergent from 0 to 10 mM sodium deoxycholate (NaDC). Bile salts showed no inhibitory effect on the lipolytic activity, whereas the calcium salts showed a stimulating action on the lipase activity. Unlike most of the lipases which were quickly denatured at the lipid/water interface, the accumulation of free fatty acids at the oil/water interface did not affect the activity of the enzyme which effectively hydrolyzed the emulsified olive oil even in the absence of bile salts. Furthermore, AFL was more active on long chain triacylglycerols than on short chain triacylglycerols. This study allowed us to prove that AFL had the interfacial activation phenomenon. A 3D structure model of AFL was built and we have concluded that the ratio hydrophobic surface/hydrophilic surface was 51% versus 50%; it could be responsible for a higher tolerance to the presence of free fatty acids at lipid/water interface.   Key words: Aspergillus flavus lipase (AFL), detergent, interfacial activation, free fatty acids, model.