The kinetics of enzymatic aldol reaction catalyzed by DERA (2-deoxyribose-5-phosphate aldolase) was studied. The reaction between acetyloxyacetaldehyde/acetaldehyde and chloroacetaldehyde/acetaldehyde in the presence of DERA produces chiral lactol intermediates, which are useful in the synthesis of optically pure super-statins. The experimental approach was designed studying batch and fed-batch reaction conditions adding different amounts of applied reactants. A three-step kinetic model was proposed including the formation of the intermediate product, synthesis of the main desired product and the synthesis of the side product by parallel non-desired secondary reaction. The kinetics of enzyme inactivation caused by reactants was also included in kinetic model design. The establishment of the kinetic model based on the two-substrates binding assuming random mechanism. After the development of the kinetic model, kinetic parameters were determined by non-linear least squares approximation search method, until the minimal differences between experimental and calculated data were achieved. The highest concentrations of the desired main product were produced in the case of fed-batch experiments applying such feeding regime that minimal surplus of reactants in the reaction mixture was attained, which consequently led to lower losses in the enzyme activity. Obtained kinetic parameters showed similar value of inactivation constant for acetyloxyacetaldehyde and acetaldehyde, whereas in the case of chloroacetaldehyde the number was significantly higher. To our knowledge, this is the first developed kinetic model describing the DERA catalyzed reaction of 2-substituted acetaldehydes to corresponding lactols. Obtained kinetic model can be used in further reactor design in the manner of optimizing the process by lowering the loss of enzyme activity in order to achieve higher amounts of the desired main product.
COBISS.SI-ID: 1752623
Dechlorination of 2,4,6-trichlorophenol was performed within a magnetically stabilized fluidized bed (MSFB), containing a palladized iron (Pd/Fe) catalyst entrapped within alginate beads. Kinetic parameters of this multistep reaction yielding phenol as a final product were preliminarily defined in a batch system using four different intermediates as substrates for Pd/Fe catalyzed dechlorination. Further work using the fluidized bed reactor provided the basis for mathematical description of the full dechlorination process both with and without the assistance of an applied magnetic field. The resulting model includes convective mass transfer in the bulk media, diffusion within the alginate beads and reaction kinetics, including catalyst deactivation caused by passivation. Very good agreement was observed between experimental data and predictions of the model. These results confirmed the benefit of using MSFB reactors for more efficient dechlorination of toxic polychlorinated phenols, as compared to fluidized bed reactors without magnetic field stabilization.
COBISS.SI-ID: 1536255171
Droplet-based liquid–liquid extraction in a microchannel was studied, both theoretically and experimentally. A full 3D mathematical model, incorporating convection and diffusion in all spatial directions along with the velocity profile, was developed to depict the governing transport characteristics of droplet-based microfluidics. The finite elements method, as the most common macroscale simulation technique, was used to solve the set of differential equations regarding conservation of moment, mass and solute concentration in a two-domain system coupled by interfacial surface of droplet-based flow pattern. The model was numerically verified and validated online by following the concentrations of a solute in two phases within the microchannel. The relative azobenzene concentration profiles in a methanol/n-octane two-phase system at different positions along the channel length were retrieved by means of a thermal lens microscopic (TLM) technique coupled to a microfluidic system, which gave results of high spatial and temporal resolution. Very good agreement between model calculations and online experimental data was achieved without applying any fitting procedure to the model parameters.
COBISS.SI-ID: 1536245187
Despite the expanding presence of microscale technology in chemical synthesis and energy production as well as in biomedical devices and analytical and diagnostic tools, its potential in biocatalytic processes for pharmaceutical and fine chemicals, as well as related industries, has not yet been fully exploited. The aim of this review is to shed light on the strategic advantages of this promising technology for the development and realization of biocatalytic processes and subsequent product recovery steps, demonstrated with examples from the literature. Constraints, opportunities, and the future outlook for the implementation of these key green engineering methods and the role of supporting tools such as mathematical models to establish sustainable production processes are discussed.
COBISS.SI-ID: 1536258243
A glucose-based vinyl surfmer, i.e. butyl polyglucoside maleic acid ester (BGMAH), was synthesized and characterized. Macroemulsion copolymerization of BGMAH with n-butyl acrylate (n-BA) was investigated. The structure of the synthesized BGMAH was confirmed using Fourier transform infrared spectroscopy and a series of 2-D homo- and heteronuclear NMR spectra. Its surfactant properties were confirmed by determination of the critical micelle concentration. The semi-batch emulsion copolymerization was monitored in situ using FTIR spectroscopy. The particle size and its distribution of the emulsions and the gel phase of the polymers were determined. The glass transition temperatures were assessed using differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA). The obtained emulsions were tested for potential application in pressure sensitive adhesives by measuring the adhesion properties of copolymer films (peel strength, tack and shear resistance). It was found that synthetic acrylates could be replaced by the modified glucose in the emulsion polymerization recipe. The adhesion properties were improved when 25 wt% of BGMAH was added in reaction mixture.
COBISS.SI-ID: 1536260035