The Influence of Some Engineering Variables Upon the Morphology of Rhizopus nigricansina Stirred Tank Bioreactor

Morphological characteristics of submerged cultures of steroid-transforming filamentous fungus Rhizopus nigricans were followed in stirred-tank bioreactors at different cultivation conditions. The influence of inoculum concentration and morphology on submerged growth of Rhizopus nigricans in the reactor was investigated. The results indicated the benefit of using inocula below 103 spores mL–1 in order to obtain pelleted growth form and to prevent undesired growth on the broth surface. Furthermore, the effect of energy dissipation rate on the morphology and biomass yield was evaluated by the use of different number and types of impellers at different agitation rates. Our study confirmed the inverse proportional relationship between energy dissipation rate and pellet diameter, which was in correlation with pellet fragmentation at high energy input

Modeling of a Pilot Wastewater Treatment Plant Operated With Variable Inflows

The nitrification-denitrification process was studied on suspended activated sludge in a CSTR pilot plant of 15 litres. The system was operated in the single sludge mode and was fed with artificial wastewater. The experiments were carried out under steady and non-steady-state operational conditions in order to assess the reliability of mathematical simulations based on a modified ASM1 model that was successfully calibrated at the starting steady-state conditions. The dynamic model predictions and the measured responses of the real process yielded the initial values when the initial steady-state operational conditions were restored after stepped changes in the input flow. Although relatively good correlations were obtained between the experimental data and the model predictions, in some cases large differences were observed under non-steady-state operational conditions. This reflects the discrepancy between the complex nature of the real activated sludge processes and the model’s macroscopic descriptions of these processes

Lattice Boltzmann Modeling-based Design of a Membrane-free Liquid-liquid Microseparator

The benefits of continuous processing and the challenges related to the integration with efficient downstream units for end-to-end manufacturing have spurred the development of efficient miniaturized continuously-operated separators. Membrane-free microseparators with specifically positioned internal structures subjecting fluids to a capillary pressure gradient have been previously shown to enable efficient gas-liquid separation. Here we present initial studies on the model-based design of a liquid-liquid microseparator with pillars of various diameters between two plates. For the optimization of in silico separator performance, mesoscopic lattice-Boltzmann modeling was used. Simulation results at various conditions revealed the possibility to improve the separation of two liquids by changing the geometrical characteristics of the microseparator. This work is licensed under a Creative Commons Attribution 4.0 International License

Theoretical Descriptions of Carbon Nanotubes Synthesis in a Chemical Vapor Deposition Reactor: A Review

The mechanisms by which carbon nanotubes nucleate and grow are still poorly understood. Understanding and mathematically describing the process is crucial for its optimization. This paper reviews different models which have been proposed to explain carbon nanotube growth in the chemical vapor deposition process. The review is divided into two sections, the first section describes some nucleation, growth and termination simulations based on molecular dynamics, and the second section describes some mathematical models based on transport and kinetics theories

Characterization of an enzymatic packed-bed microreactor: Experiments and modeling

A micro packed-bed reactor (µPBR) based on two-parallel-plates configuration with immobilized Candida antarctica lipase B in the form of porous particles (Novozym® 435) was theoretically and experimentally characterized. A residence time distribution (RTD) within µPBRs comprising various random distributions of particles placed in one layer was computationally predicted by a mesoscopic lattice Boltzmann (LB) method. Numerical simulations were compared with measurements of RTD, obtained by stimulus-response experiment with a pulse input using glucose as a tracer, monitored by an electrochemical glucose oxidase microbiosensor integrated with the reactor. The model was validated by a good agreement between the experimental data and predictions of LB model at different conditions. The developed µPBR was scaled-up in length and width comprising either a single or two layers of Novozym® 435 particles and compared regarding the selected enzyme-catalyzed transesterification. A linear increase in the productivity with the increase in all dimensions of the µPBR between two-plates demonstrated very efficient and simple approach for the capacity rise. Further characterization of µPBRs of various sizes using the piezoresistive pressure sensor revealed very low pressure drops as compared to their conventional counterparts and thereby great applicability for production systems based on numbering-up approach

Modelling of L-DOPA Oxidation Catalyzed by Laccase

Enzymatic oxidation of 3,4-dihydroxyphenyl-L-alanine (L-DOPA) with laccase from Trametes versicolor was investigated. The highest enzyme activity at pH 5.4 and at 25 ºC was found. The reaction kinetics and the effect of dissolved oxygen concentration on the reaction rate were evaluated. A mathematical model, comprised of double-substrate Michealis-Menten kinetics and mass balances for L-DOPA and dissolved oxygen concentrations, was developed in order to describe and predict the process of L-DOPA oxidation. Kinetic parameters, , and were estimated and experimentally verified by a set of experiments with constant additional aeration for different initial concentrations of L-DOPA and dissolved oxygen. A significant increase in reaction rate was established at a higher oxygen concentration in the inlet gas. The developed model was used to investigate the influence of dissolved oxygen concentration on L-DOPA conversion