Appl Microbiol Biotechnol(1990) 33:255-258 Applied Microbiology Biotechnology © Springer-Verlag1990 Interesterification of phosphatidylcholine with lipases in organic media Ingemar Svensson, Patrick Adlercreutz, and Bo Mattiasson Department of Biotechnology, ChemicalCenter, Universityof Lund, P. O. Box 124, S-22100 Lund, Sweden Received 18 October 1989/Accepted 23 January 1990 Summary. Lipases were investigated with respect to their ability to catalyse the incorporation of fatty acids into phosphatidylcholine (PC) by interesterification reactions. The enzymes were dried onto solid support materials and the conversions were carried out in wa- ter-saturated toluene. Three lipases (two fungal and one plant enzyme) had the desired activity; immobilized li- pase from Mucor miehei (Lipozyme) was the most ac- tive enzyme. The Lipozyme-catalysed interesterification was selective for the sn-1 position of PC and during 48 h of reaction around 50% of the fatty acids in this position were replaced with heptadecanoic acid, a fatty acid which was practically absent in the original phos- pholipid. Due to adsorption on the support material and the competing hydrolysis reaction the total amount of PC in the reaction solution decreased to about 40% of the original amount. Higher interesterification rates were obtained with free fatty acids as acyl donors than with fatty acid esters. Introduction The use of biocatalysts in organic media has attracted much interest in recent years (Laane et al. 1987). One reason is that in organic media hydrophobic com- pounds such as lipids can be dissolved and thereby made accessible for enzymatic conversion. Another reason is that in organic media enzymatic reactions that are not feasible in aqueous solutions can be carried out. An example of such a reaction is the interestification reaction which is effectively suppressed in water by the competing hydrolysis reaction. Phospholipids from natural sources contain several fatty acids and their proportion depends on the source. For scientific purposes and possibly for some practical applications it is desirable to have phospholipids con- taining specific fatty acids. Phospholipids with speci- fied fatty acid compositions can sometimes be obtained Offprint requests to: I. Svensson by fractionation of natural phospholipids, but the most common approach is to synthesize the desired com- pounds. One promising synthetic approach is to use natural phospholipids as a starting material and replace the existing fatty acids with the desired ones. Enzymatic synthetic methods are characterized by mild reaction conditions and high selectivity, and this can be expected to be of great importance in the trans- formation of phospholipids. Two groups of enzymes are the most likely to catalyse interesterifications of phospholipids: phospholipases and lipases. Phospholi- pase A1 and A2 are specific for the hydrolysis of the fatty acids in the sn-1 and sn-2 positions respectively, and it is possible that these enzymes can also be used to catalyse interesterification reactions. The natural sub- strates of lipases are triglycerides, but many of these en- zymes have very broad substrate specificity and have been used for breaking and forming ester bonds in a wide variety of compounds. There are several reports that the fatty acids of triglycerides can be exchanged using lipase-catalysed interesteification reactions (Ma- crae 1983; Wisdom et al. 1987). There is one report in the literature in which enzy- matic interesterification of phospholipids has been achieved (Yoshimoto et al. 1986). Candida cylindracea lipase was covalently modified with polyethylene glycol (PEG) so that it could be dissolved in benzene. Under the reaction conditions used, hydrolysis was the domi- nating reaction, and the incorporation of the new fatty acid due to the interesterification reaction was rather low. In the present work, a quite different kind of bio- catalyst was used. Lipases adsorbed on solid supports were suspended in the reaction medium, which con- tained phosphatidytcholine (PC) and the fatty acid to be incorporated dissolved in toluene. Different fatty acids and fatty acid esters were used as acyl donors. Materials and methods Chemicals. Phosphatidylcholine (PC, purity 98.5% from egg, aver- age molecular weight 790 g/tool) was a gift from Karlshamns,