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Sungkorn R.,University of Graz | Derksen J.J.,University of Alberta | Khinast J.G.,Research Center Pharmaceutical Engineering
AIChE Journal

Simulations of a gas-liquid stirred reactor including bubble breakage and coalescence were performed. The filtered conservation equations for the liquid phase were discretized using a lattice-Boltzmann scheme. A Lagrangian approach with a bubble parcel concept was used for the dispersed gas phase. Bubble breakage and coalescence were modeled as stochastic events. Additional assumptions for bubble breakup modeling in an Euler-Lagrange framework were proposed. The action of the reactor components on the liquid flow field was described using an immersed boundary condition. The predicted number-based mean diameter and long-term averaged liquid velocity components agree qualitatively and quantitatively well with experimental data for a laboratory-scale gas-liquid stirred reactor with dilute dispersion. Effects of the presence of bubbles, as well as the increase in the gas flow rate, on the hydrodynamics were numerically studied. The modeling technique offers an alternative engineering tool to gain detailed insights into complex industrial-scale gas-liquid stirred reactors. © 2011 American Institute of Chemical Engineers (AIChE). Source

Planchette C.,University of Marne-la-Vallee | Planchette C.,Research Center Pharmaceutical Engineering | Biance A.-L.,University Claude Bernard Lyon 1 | Pitois O.,University Paris Est Creteil | Lorenceau E.,University Paris Est Creteil
Physics of Fluids

Armored interfaces refer to fluid interfaces on which a compact monolayer of particles is adsorbed. In this paper, we probe their robustness under impact. For such an investigation, the impact of a drop (covered or not by particles) on a flat armored interface is considered. Two regimes are observed: small drops impacting at low velocities do not coalesce, while bigger drops falling at higher velocities lead to coalescence. The coalescence which occurs when the impacting drop has just reached its maximum extension directly results from the formation of bare regions within the armor. We therefore propose a geometric criterion to describe this transition. This simple modeling is able to capture the dependence of the measured velocity threshold with particle size and drop diameter. The additional robustness experienced by double armors (both drop and puddle covered) results in an increase of the measured velocity threshold, which is quantitatively predicted. © 2013 AIP Publishing LLC. Source

Lorantfy B.,Vienna University of Technology | Lorantfy B.,Research Center Pharmaceutical Engineering | Seyer B.,Vienna University of Technology | Herwig C.,Vienna University of Technology
New Biotechnology

Extreme halophilic Archaea are extremophile species which can thrive in hypersaline environments of up to 3-5. M sodium chloride concentration. Although their ecology and physiology are widely identified on the microbiological level, little emphasis has been laid on quantitative bioprocess development with extreme halophiles.The goal of this study was to establish, on the one hand, a methodological basis for quantitative bioprocess analysis of extreme halophilic Archaea with an extreme halophilic strain as an example. Firstly, as a novel usage, a corrosion resistant bioreactor setup for extreme halophiles has been implemented. Then, paying special attention to total bioprocess quantification approaches, an indirect method for biomass quantification using on-line process signals was introduced. Subsequently, robust quantitative data evaluation methods for halophiles could be developed, providing defined and controlled cultivation conditions in the bioreactor and therefore obtaining suitable quality of on-line as well as off-line datasets.On the other hand, new physiological results of extreme halophiles in bioreactor have also been obtained based on the quantitative methodological tools. For the first time, quantitative data on stoichiometry and kinetics were collected and evaluated on different carbon sources. The results on various substrates were interpreted, with proposed metabolic mechanisms, by linking to the reported primary carbon metabolism of extreme halophilic Archaea. Moreover, results of chemostat cultures demonstrated that extreme halophilic organisms show Monod-kinetics on different sole carbon sources. A diauxic growth pattern was described on a mixture of substrates in batch cultivations.In addition, the methodologies presented here enable one to characterize the utilized strain Haloferax mediterranei (HFX) as a potential new host organism. Thus, this study offers a strong methodological basis as well as a fundamental physiological assessment for bioreactor quantification of extreme halophiles that can serve as primary knowledge for applications of extreme halophiles in biotechnology. © 2013 Elsevier B.V. Source

Teubl B.J.,University of Graz | Absenger M.,Medical University of Graz | Frohlich E.,Medical University of Graz | Leitinger G.,Medical University of Graz | And 3 more authors.
European Journal of Pharmaceutics and Biopharmaceutics

An important area for future research lies in finding a drug delivery system across or into the oral mucosa. However, to design such systems, simplified biological models are necessary so that the mechanisms and/or interactions of interest can readily be studied. The oral epithelium is covered by a complex mucus layer, which enables exchange of nutrients and provides lubrication. However, it has been demonstrated that mucus has an impact on the mobility of nanoparticles and drug molecules. Thus, we aimed to develop an advanced buccal in vitro model for studying transport of nanoparticles, taking the mucus layer into account. First, animal mucins (porcine gastric, bovine submaxillary) were compared with natural human mucin regarding chemical and morphological structure. Second, an "external" mucus layer was prepared by a film method and deposited onto an oral cell line (TR 146), cultured on transwells®. Adherence of the mucin fibers was evaluated and the viability of the model was assessed. Nanoparticle transport studies were performed with this advanced in vitro model and an ex vivo diffusion system. The results revealed that porcine mucin is most similar to human natural mucin in chemical structure and morphology. Both the bovine and porcine mucin fibers adhered onto the oral cells: Due to the different morphology of bovine mucin, the viability of the oral cells decreased, whereas porcine mucin maintained the viability of the model for more than 48 h. Comparison of in vitro data with ex vivo data suggested reliability of the advanced buccal in vitro model. Additionally, it was demonstrated that the mucus layer in the oral cavity also acts as a strong barrier for the mobility of nanoparticles. © 2013 Elsevier B.V. All rights reserved. Source

Neugebauer P.,University of Graz | Khinast J.G.,University of Graz | Khinast J.G.,Research Center Pharmaceutical Engineering
Crystal Growth and Design

Protein crystals have many important applications in many fields, including pharmaceutics. Being more stable than other formulations, and having a high degree of purity and bioavailability, they are especially promising in the area of drug delivery. In this contribution, the development of a continuously operated tubular crystallizer for the production of protein crystals has been described. Using the model enzyme lysozyme, we successfully generated product particles ranging between 15 and 40 μm in size. At the reactor inlet, a protein solution was mixed with a crystallization agent solution to create high supersaturations required for nucleation. Along the tube, supersaturation was controlled using water baths that divided the crystallizer into a nucleation zone and a growth zone. Low flow rates minimized the effect of shear forces that may impede crystal growth. Simultaneously, a slug flow was implemented to ensure crystal transport through the reactor and to reduce the residence time distribution. © 2015 American Chemical Society. Source

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