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Enhancement of Phenolic Compounds Oxidation Using Laccase from Trametes versicolor in a Microreactor
Ana Jurinjak Tušek,Marina Tišma,Valentina Bregovic,Ana Pticar,Želimir Kurtanjek,Bruno Zelic 한국생물공학회 2013 Biotechnology and Bioprocess Engineering Vol.18 No.4
Laccases catalyse the oxidation of a wide range of substrates by a radical-catalyzed reaction mechanism,with a corresponding reduction of oxygen to water in a four-electron transfer process. Due to that, laccases are considered environmentally friendly enzymes, and lately there has been great interest in their use for the transformation and degradation of phenolic compounds. In this work, enzymatic oxidation of catechol and L-DOPA using commercial laccase from Trametes versicolor was performed, in continuously operated microreactors. The main focus of this investigation was to develop a new process for phenolic compounds oxidation, by application of microreactors. For a residence time of 72 s and an inlet oxygen concentration of 0.271 mmol/dm3, catechol conversion of 41.3% was achieved, while approximately the same conversion of L-DOPA (45.0%) was achieved for an inlet oxygen concentration of 0.544 mmol/dm3. The efficiency of microreactor usage for phenolic compounds oxidation was confirmed by calculating the oxidation rates;in the case of catechol oxidation, oxidation rates were in the range from 76.101 to 703.935 g/dm3/d (18 - 167 fold higher, compared to the case in a macroreactor). To better describe the proposed process, kinetic parameters of catechol oxidation were estimated, using data collected from experiments performed in a microreactor. The maximum reaction rate estimated in microreactor experiments was two times higher than one estimated using the initial reaction rate method from experiments performed in a cuvette. A mathematical model of the process was developed, and validated, using data from independent experiments.
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Mass transfer coefficient of slug flow for organic solvent-aqueous system in a microreactor
Ana Jurinjak Tušek,Iva Anić,Želimir Kurtanjek,Bruno Zelić 한국화학공학회 2015 Korean Journal of Chemical Engineering Vol.32 No.6
Application of microreactor systems could be the next break-through in the intensification of chemical and biochemical processes. The common flow regime for organic solvent-aqueous phase two-phase systems is a segmented flow. Internal circulations in segments cause high mass transfer and conversion. We analyzed slug flow in seven systems of organic solvents and aqueous phase. To analyze how slug lengths in tested systems depend on linear velocity and physical and chemical properties of used organic solvents, regression models were proposed. It was shown that models based on linearization of approximation by potentials give low correlation for slug length prediction; however, application of an essential nonlinear model of multiple layer perceptron (MLP) neural network gives high correlation with R2=0.9. General sensitivity analysis was applied for the MLP neural network model, which showed that 80% of variance in slug length for the both phases is accounted for the viscosity and density of the organic phases; 10% is accounted by surface tension of the organic phase, while molecular masses and flow rates each account for 5%. For defined geometry of microreactor, mass transfer has been determined by carrying out the neutralization experiment with NaOH where acetic acid diffuses from organic phase (hexane) into aqueous phase. Estimated mass transfer coefficients were in the range kLa=4,652-1,9807 h−1.
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Tamara Jurina,Ana Jurinjak Tušek,Mirjana Curlin 한국생물공학회 2015 Biotechnology and Bioprocess Engineering Vol.20 No.6
Environmental distribution and bioremediation of hydrocarbon pollutants is described in the literature with complex mathematical models. Better understanding and easier model application require detailed model analysis. In this work, local sensitivity analysis of the kinetic parameters and metabolic control analysis of the biological part of the integrated BTEX bioremediation model were performed. Local sensitivity analysis revealed that the dissolved oxygen concentration (SO) and particulate iron (III) oxide concentration (SFe) were the most sensitive to both positive and negative parameter value perturbations. In the case of model reactions, aerobic growth (r1) and aerobic growth on acetate (r13) were observed to be the most sensitive. The elasticity, flux control, and concentration control coefficients were estimated by applying the metabolic control analysis methodology. Metabolic control analysis revealed a positive effect of ammonium on all analysed model reactions. The results also indicated the importance of perturbation of the enzyme level catalysing iron reduction on acetate on model fluxes, as well as the importance of enzyme level catalysing aerobic growth on model metabolite concentration. These results can be used in planning optimal operating strategy for BTEX bioremediation.
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