Strategies for the enzymatic enrichment of PUFA from fish oil

Encapsulation of EPA and DHA concentrate from Kilka fish oil by milk proteins and evaluation of its oxidative stability

Glyceride product from lipase-catalyzed hydrolysis of fish oil (large-scale) is a rich source of n-3 PUFA (49.62%); but it is prone to oxidation. Our aim was to encapsulate this product by a mixture of whey powder and sodium caseinate (4:1) as a new wall material. The emulsification was done using ultrasonication in different powers (180-380 W) and times (1-3 min) and, then, the emulsions were freeze-dried to obtain the powders. Based on encapsulation efficiency, sonication (88-94%) could inhibit the presence of oil at the surface of powder particles in comparison with the samples prepared without sonication (control, 68%). The highest oxidation rate and the lowest L-value were found for the unencapsulated glyceride product stored in air atmosphere followed by the control powder, the powders from sonication treatment and the unencapsulated glyceride product under N₂, respectively. In the case of oxidative stability of the samples, the sonication time was more significant than sonication power. According to our results, a sonication treatment of 380 W for 3 min was recommended to prepare parent emulsions during fish oil encapsulation.

Quantitative analysis of enzymatic fractionation of multiple substrate mixtures

The enzymatic conversion of mixtures of multiple substrates was studied quantitatively, based on established methodology used for the enzymatic kinetic resolution of racemic mixtures, involving the use of competitive factors: ratios of specificity constants (k(cat)/K(M)) of substrate pairs. The competitive factors of the substrates were defined in relation to a reference substrate. These competitive factors were used to predict the composition of the reaction mixture as a function of the degree of conversion of the reaction. The methodology was evaluated using three different lipases to hydrolyze a model mixture of four fatty acid methyl esters and for the esterification of a mixture of the same fatty acids in free form with ethanol. In most cases, the competitive factors determined from the initial phase of the reactions predicted the product composition during the rest of the reaction very well. The slowest reacting fatty acid was erucic acid (both in free form and as methyl ester), which was thus enriched in the remaining substrate fraction, while the other fatty acids: lauric acid, palmitic acid and oleic acid were converted faster. Simulations of the compositions of reaction mixtures with different values of the competitive factors were carried out to provide an overview of what could be achieved using enzymatic enrichment. Possible applications include reactions involving homologous substrates and mixtures of multiple isomers. The analysis presented provides guidelines that can be useful in the screening and development of enzymes for enzymatic enrichment applications.