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Mikroreaktori sa svojim tipičnim dimenzijama mikrokanala u području 10 μm – 500 μm karakterizirani su mnogo većom međufaznom površinom u odnosu na konvencionalne reaktorske sustave. Posljedično se zbog ovoga ostvaruje intenzivniji prijenos tvari i topline što doprinosi povećanju konverzije te nastajanje manje količine sporednih produkata. Također su zbog malog reaktorskog volumna za provedbu eksperimenta potrebne male količine kemikalija. Osim ovoga upotrebom mikroreaktora povećavaju se doseg reakcije i sigurnost provedbe procesa. U ovom radu provedena je biotransformacija fenola enzimom lakaza porijeklom iz Trametes versicolor u mikroreaktoru. Konverzija i kinetički parametri jednosupstratne Michaelis-Menteničine kinetike procijenjeni u mikroreaktoru uspoređeni su s onima dobivenim pokusima provedenim u kotlastom reaktoru. Biotransformacija fenola provedena je u tri različita dvofazna sustava voda-organsko otapalo (diklormetan, heksan i toluen) pri čemu je enzim lakaza bio u vodenoj fazi, a fenol u organskom otapalu. U svakom od promatranih sustava provedena je analiza stabilnosti enzima lakaze. Za svaki od analiziranih sustava voda-organsko otapalo provedena je i analiza profila strujanja u mikrokanalu pri različitim protocima i omjerima vode i organskog otapala. Zaključeno je da je kod malih vrijednosti Reynoldsova broja do Re = 1,2 i kapilarnog broja do Ca = 1,3∙10-4 dominantno segmentirano strujanje, dok se kod Reynoldsovih brojeva većih od Re = 1,3 i kapilarnih brojeva većih od Ca = 2,1∙10-4 razvija paralelno strujanje. U šaržnom reaktoru postignute su sljedeće maksimalne konverzije: Xvoda-diklormetan = 28,49 %, Xvoda-heksan = 23,46 % i Xvoda-toulen = 32,79 % dok su u mikroreaktoru za vrijeme zadržavanja τ = 240 s postignute sljedeće konverzije: Xvoda-diklormetan = 79,28 %, Xvoda-heksan = 77,05 % i Xvoda-toulen = 79,28 %. Procijenjene vrijednosti maksimalnih brzina reakcije biotransformacije fenola enzimom lakaza u mikroreaktoru su približno 100 puta veće od onih procijenjenih u kotlastom reaktoru za pojedino otapalo. Kao najpogodnije otapalo za provedbu reakcije u kotlastom reaktoru i mikroreaktoru pokazao se toluen jer su u pokusima provedenim u sustavu voda-toluen procijenjeni najveća maksimalna brzina reakcije i najveći afinitet prema enzimu lakazi te je postignuta najveća konverzija. Microreactors with typical dimension of microchannels in range of 10 μm to500 μm are characterized with much greater interfacial area in comparison to conventional reactors. As a result there is much more intense mass and heat transfer what leads to larger conversions and smaller quantities of byproducts. Also, because of small reaction volume conducting the experiment requires small quantities of chemicals. Additionally, the use of microreactors increases conversion and process safety. In this work biotransformation of phenol using laccase from Trametes versicolor in a microreactor was performed. Conversion and kinetic parameter of single substrate Michaelis-Menten kinetics were estimated for microreactor experiments and compared with those obtained in a batch reactor. Biotransformation of phenol was conducted in three different two-phase systems water-organic solvent (dichloromethane, hexane, and toluene). Enzyme laccase was in aqueous phase and toluene in organic solvent. In every system analysis of laccase stability was performed. For every of the analyzed water-organic solvent systems flow patterns in microchannel with different flows and different water to organic solvent ratio were analyzed. It was concluded that in small Reynolds numbers up to Re = 1.2 and capillary numbers up to Ca = 1.3∙10-4 segmented flow patterns are dominant, while parallel profile is developed at Reynolds numbers larger than Re = 1.3 and capillary numbers larger than Ca = 2.1∙10-4 . In batch rector maximal conversion of Xwater-dichloromethane = 28.49 %, Xwater-hexane = 23.46 % and Xwater -toluene = 32.79 % were reached while in a microreactor for residence time τ = 240 s conversion of X water-dichloromethane = 79.28 %, X water-hexane = 77.05 % and Xwater-toluene = 79.28 % were reached. Values of estimated maximal reaction rate of laccase catalyzed phenol biotransformation were approximately 100 fold higher than ones estimated in a batch reactor for every solvent. Toluene was the most suitable solvent for the reaction in the batch and the microreactor because in performed experiments in water-toluene systems maximal reaction rate was estimated, the affinity of enzyme laccase was also maximal and consequently the maximal conversion was achieved. |
