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The aim of this dissertation is to investigate the influence of type and concentration of surfactants, the presence of bile acids (BA), the concentration of Ca2 and other factors on the enzymatic lipolysis of triglycerides (TG) and the phase distribution of cholesterol and reaction products, by using colloid and bio-physical methods. The main conclusions of the dissertation can be summarized as follows: 1. We found that all studied surfactants inhibit lipolysis in the presence and absence of BA. The major mechanism of inhibition is the formation of a dense surfactant adsorption layer on the oil-water interface, which does not allow the enzyme to come into direct contact with the TG substrate. 2. We demonstrated that the reactivation of the lipase in presence of BA is caused by the displacement of the surfactant molecules from the oil-water interface, due to their solubilization in the BA micelles. We showed that there exists an optimal surfactant/BA ratio, at which lipolysis is facilitated by the increased kinetics of transfer of reaction products into the aqueous phase, which prevents the formation of precipitates on the surface of the oil droplets. 3. We developed a new in vitro lipolysis procedure that reproduces well in vivo conditions, including the pH profile in the small intestine. We applied that procedure to find that solubilized cholesterol increases linearly with the increase of solubilized fatty acids (FA). We also showed that Ca2 reduces cholesterol solubilization in the aggregates of BA smaller than 200 nm. This effect is explained by the precipitation of solubilized FA by Ca2 , which then leads to decrease of the co-solubilized cholesterol.
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