The catalytic behavior of lipases from various sources is examined in a series of nanodispersed systems, such as microemulsions. The studies focus on the catalysis of hydrolytic reactions of triglycerides, as well as synthetic esterification reactions of high added value products. Detailed kinetic studies and mechanism determinations of the enzymatic reactions are carried out in the specific nanoenvironments.
The most recent studies dealt with the catalytic behavior of lipases from the Mucor miehei and C. antarctica B microorganisms in a special type of microemulsions formed in the absence of a classic surfactant.
More specifically the ternary system hexane - 1-propanol - water was tested as a convenient medium for carrying out synthetic reactions of alcohols with fatty acids or phenolic acids. The results indicated that the system is quite adequate for such biocatalytic transformations especially in the case of substrates with very poor solubility such as the phenolic acids. The absence of surfactant facilitates the isolation of the products and allows the extension of the project towards bioconversions of specific antioxidant phenolic acids, which through esterification with lipophilic alcohols can be incorporated to foods with a lipid environment (e.g. margarines).
In parallel, proteolytic enzymes such as trypsin and a- chymotrypsin are studied in various microemulsions. The effect of various parameters affecting the enzyme activity as well as the structure of the biomolecule in the reverse micelles were examined. The most recent studies were focused on the increase of the enzyme stability in the specific environment aiming at extending the shelf-life of the cosmetic products we have developed.
Schematic representation of the biocatalytic transformation of lipophilic substrates (S) by lipase (Å) in nanodispersions
Relevant publications:
M. Zoumpanioti, H. Merianou, T. Karandreas, H. Stamatis, A. Xenakis (2010) "Esterification of phenolic acids catalyzed by lipases immobilized in organogels" Biotechnol. Lett. 32, 1457-62
A. Xenakis, V. Papadimitriou, H. Stamatis, F. N. Kolisis (2009) "Biocatalysis in microemulsuions" in "Microemulsions: Properties and Applications" Surfactant Sci.Ser., Vol.144, pp.349-385. Ed. M.Fanun.,CRC Press, Jerusalem, Israel
M. Zoumpanioti, P. Parmaklis, P. Dominguez de Maria, H. Stamatis, J.V. Sinisterra, A. Xenakis. (2008) "Esterification reactions catalyzed by lipases immobilized in organogels. Effect of temperature and substrate diffusion" Biotechnol. Lett. 30,1627-1631
M. Zoumpanioti, M. Karali, A. Xenakis & H. Stamatis, (2006) "Lipase biocatalytic processes in surfactant free microemulsion - like ternary systems and related organogels". Enzym. Microb. Technol., 39, 531-539.
