Strategies for lipase-catalyzed production and purification of structured phospholipids

This work provides different strategies for the enzymatic modification of the fatty acid composition in soybean phosphatidylcholine (PC) and the subsequent purification. Enzymatic transesterification reactions with caprylic acid as acyl donor were carried out in continuous enzyme bed reactors with a commercial immobilized lipase (Lipozyme RM IM) as catalyst.

Operative stability of the immobilized lipase was examined under solvent and solvent-free conditions. The long reaction time required to have a high incorporation, combined with rapid deactivation of the enzyme, makes the solvent-free transesterification reaction unfavorable. Performing the reaction in the presence of solvent (hexane) makes it possible to have high incorporation into PC and deactivation of the lipase is less pronounced as compared to solvent-free operations.

For solvent-free operation, it is suggested to recycle the reaction mixture through the packed bed reactor, as this would increase incorporation of the desired fatty acids, due to increased contact time between substrate and enzyme in the column. Removal of free fatty acids from the reaction mixture can be done by ultrafiltration; however, parameters need to be selected with care in order to have a feasible process.

No changes are observed in the phospholipid (PL) distribution during ultrafiltration, and other techniques as column chromatography may be required if high purity of individual PL species is desired. LC/MS analysis of transesterified PC revealed the presence of 8:0/8:0-PC, showing that acyl migration takes place during the acidolysis reaction.