|Opis:||Lactic acid esters, which are widely used in the food, pharmaceutical and cosmetics industries are among the most important derivatives of lactic acid. Nowadays the biodegradability of the products and the use of environment-friendly technologies are of great importance, therefore a appropriate solvent for the synthesis of lactate esters should be choosen. In stead of aqueous medium, enzyme catalyzed reactions could be performed in conventional organic solvents or in nonconventional solvents, such as supercritical fluids and ionic liquids.
The purpose of the dissertation was to carry out the enzymatic synthesis of lactate esters, specifically n-butyl lactate in nonconventional solvents. As the nonconventional solvents, the supercritical fluids (supercritical carbon dioxide, supercritical trifluoromethane and supercritical ethane) and ionic liquid (CYPHOS IL-201) were used. All used solvents present an interesting class of solvents for enzyme-catalyzed reactions.
The immobilized lipase B from Candida antarctica was successfully used as a biocatalyst for the enzyme-catalyzed esterification of D,L-lactic acid with n-butanol in a high-pressure batch stirred-tank reactor. The influence of substrates ratio (D,L-lactic acid:n-butanol), concentration of molecular sieves, stirring rate, multiple use of the enzyme, pressure, temperature and concentration of co-solvent (n-hexane) on the efficiency of D,L-lactic acid, yield (productivity) and the initial rate of formation of the n-butyl lactate ester was studied when the reaction was performed in supercritical carbon dioxide. Also, the reaction parameters, such as, pressure, temperature and concentration of co-solvent (n-hexane) were optimized when the enzymatic esterification was carried out in the supercritical trifluoromethane. In the systems supercritical carbon dioxide/ionic liquid and supercritical trifluoromethane/ionic liquid, the impact of the concentration of ionic liquids CYPHOS IL-201, temperature, pressure and concentration of the enzyme of the reaction were studied.
Furthermore, the antimicrobial activity of enzyme synthesized n-butyl lactate against a variety of test microorganisms (Saccharomyces cerevisiae, Aspergillus niger, Trichoderma viride, Penicillium cyclopium, Escherichia coli, Pseudomonas fluorescens and Bacillus cereus) was determined. |