Βιομετασχηματισμοί φυσικών αντιοξειδωτικών σε ιοντικά υγρά

• Main Authors: Κατσούρα, Μαρία, Katsoura, Maria
• Format: Doctoral or Postdoctoral Thesis
• Language: Greek
• Published: University of Ioannina 2010
• Subjects: Βιοκαταλυτική τροποποίηση; Φυσικά αντιοξειδωτικά; Μικροβιακές λιπάσες; Ιοντικά υγρά; Ενζυμική σταθερότητα; Δομή λιπασών σε ιοντικά υγρά; Αντιοξειδωτική δράση λιπόφιλων παραγώγων; Biocatalytic lipophilization; Natural antioxidants; Microbial lipases; Ionic liquids; Enzyme stability; Lipase structure in ionic liquids; Antioxidant activity of lipophilic derivatives; Φυσικές Επιστήμες; Βιολογία; Natural Sciences; Biological Sciences; Antarc*; Antarctica
• Online Access: http://hdl.handle.net/10442/hedi/19747; https://doi.org/10.12681/eadd/19747

The present study focuses on the development of a novel biocatalytic process for the modification of the structure of natural antioxidants, employing “green”, environmentally friendly and non toxic ionic liquids as reaction media. The enzymatic modification of natural antioxidants is performed through acylation reactions catalyzed by the “work horses” of biotechnology, i.e. lipases, aiming at the synthesis of lipophilic derivatives of natural antioxidants. The importance of the feasibility of this biocatalytic process lies not only in the synthesis of lipophilic biologically active derivatives of natural antioxidants which can be applied in pharmaceutical, cosmetic and food industries, but also in the clarification and understanding of the catalytic properties and structure-function relationships of lipases in this novel category of non-conventional media. In this sense, the thermal stability of two microbial lipases, lipase B from Candida antarctica and lipase from Rhizomucor miehei, was studied in several imidazolium based BF4 - - or PF6 --containing ionic liquids. The study shows that the use of ionic liquids results in the stabilization or even, in some cases, activation of the used lipases. The significant stabilization of lipases in ionic liquids is considered to be highly advantageous, especially in comparison to conventional organic solvents widely employed for the modification of natural compounds, such as antioxidants. Several parameters, such as the type of enzyme preparation (immobilized, lyophilized or free), type of immobilization carrier, incubation temperature, water content and ionic liquid nature, were found to affect lipase stability in ionic liquids. The ionic composition of ionic liquids imposes a considerable effect, as in all cases stability was improved with the elongation of the alkyl chain of imidazolium cation and in the presence of PF6 - as compared to the BF4 - anion. This result can be attributed to the significant effect of different ionic liquids, depending on their properties ...