Novel applications of lipases: Dissertation

Lipases are highly versatile enzymes, which can be used for the catalysis of several reactions with a broad range of substrates to produce a variety of products. Especially the use of lipases to catalyze reactions in non-aqueous media has opened up many new synthetic possibilities and potential applications in the food, cosmetic and pharmaceutical industries. Applications of lipase-catalyzed hydrolysis, esterification, stereoselective esterification and transesterification reactions in aqueous and solvent-free conditions and in organic solvents were studied in the present investigation. Several lipases from different sources were characterized with respect to their lipolytic activities and biochemical properties in order to be able to use commercial enzyme preparations without further purification. For use in organic solvents, lipases were immobilized by adsoption on solid carriers. The use of immobilized Aspergillus niger, Candida rugosa and Pseudomonas fluorescens lipases in the synthesis of fatty acid esters and in the transesterification of triacylglycerol with fatty acids was focused mainly on the effect of the immobilization method. The correlations between hydrolytic, synthetic and transesterification activities were considered. The synthetic activities of the immobilized enzymes could be predicted from their hydrolytic activities: the higher the hydrolytic activity, the higher was the synthetic activity. However, no direct correlation was observed between the hydrolytic and transesterification activities of lipases in the transesterification. The modification of phospholipids was studied by lipase-catalyzed hydrolysis and transesterification. The efficiency of lipases from A. niger and Penicillium cyclopium, phospholipases A1 and A2 from A. niger and pancreatic phospholipase A2 were compared in the hydrolysis of soybean phospholipids. In the transesterification of a synthetic phospholipid with fatty acid, the water content in the reaction mixture was shown to have a major effect on the catalytic efficiency of immobilized A. niger and Rhizomucor miehei lipases. The benefits of solvent-free media over solvent-based media were compared. A method for the resolution of enantiomers of racemic ibuprofen via stereoselective esterification catalyzed by C. rugosa lipase was presented. The study focused on the types of solvent and alcohol moiety, on the water content and on reaction temperature. Of the new applications of lipases in papermaking processes, the ability of C. rugosa lipase to degrade various harmful lipophilic esters present in extractives of fresh in birch and birch sulphate pulp was demonstrated.