Mathematical modelling of biocatalytical synthesis of nanoparticles

U ovom radu provedena je sinteza nanočestica kalcijevog karbonata pomoću produkata biokatalitičke hidrolize uree i enzima ureaze. Uz to ispitivana je kinetika hidrolize uree uz enzim ureazu te je promatran utjecaj kalcijevih (Ca2+) iona na aktivnost enzima. Reakcije su provedene u dva medija – redestiliranoj vodi i 10%-tnoj otopini Tritona x-100, pri dvije temperature, T = 30°C i T = 20°C. Ispitivanje kinetike reakcije provedeno je mjerenjem početne brzine reakcije pri različitim koncentracijama uree, uz stalnu koncentraciju enzima ureaze. Kinetika reakcije opisana je jednosupstratnom Michaelis – Menteničinom kinetikom. Utjecaj kalcijevih iona (Ca2+) na aktivnost enzima ispitan je mjerenjem specifične aktivnosti ureaze u ovisnosti o različitim koncentracijama kalcijeva klorida, CaCl2, uz stalnu koncentraciju uree i ureaze. Utvrđeno je da kalcijevi ioni inhibiraju ureazu nekompetitivnom inhibicijom. Razvijen je matematički model procesa koji je validiran provođenjem reakcije u kotlastom reaktoru uz stalno miješanje na termostatiraoj tresilici. Reakcijom kalcijevih iona s produktima hidrolize uree istaložene su nanočestice kalcijevog karbonata koje su karakterizirane pomoću pretražnog elektronskog mikroskopa.In this study synthesis of calcium carbonate nanoparticles was carried out using products of biocatalytical hydrolysis of urea catalyzed by enzyme urease. Kinetics of the urease-catalyzed hydrolysis of urea and the influence of Ca2+ ions on enzyme activity was tested. Reactions were carried out in two different media – redistilled water and 10% Triton x-100 solution at two temperatures, T = 30°C and T = 20°C. Reaction kinetics was experimentally determined using the initial reaction rate method. Reaction kinetics was described with Michaelis – Menten kinetic model. Influence of calcium ions (Ca2+) on the enzyme activity was tested by measuring the specific activity of urease as a function of various concentrations of calcium chloride, CaCl2, with a constant concentration of urea and urease. It was found that Ca2+ ions inhibit urease with non – competitive inhibition. Mathematical model of the process was developed and validated in a batch reactor. Nanoparticle synthesis was carried out by adding calcium chloride into a solution of urea and enzyme urease. In the reaction of calcium ions and urea hydrolysis products, calcium carbonate nanoparticles were precipitated. Synthesized nanoparticles were characterized with scanning electron microscope