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Airlift Bioreactor (airlift + bioreactor)

Distribution by Scientific Domains

Chemistry	61%
Life Sciences	30%

Selected Abstracts

Modified volume expansion method for measuring gas holdup

THE CANADIAN JOURNAL OF CHEMICAL ENGINEERING, Issue 2 2002
Annie X. Meng
Abstract A simple, modified volume expansion method, or inclined tube method, is compared to the pressure difference method for determining gas holdup in an airlift bioreactor. The modified volume expansion method could be used for all pneumatic bioreactors where fluid fluctuation is vigorous and visual observation of the continuous phase rise is difficult. The overall gas holdup data measured using the inclined tube method are shown to be very close to overall gas holdup determined using a gamma ray density monitor system. However, the overall gas holdup measured by the pressure difference method is found to be significantly different. This difference is due to energy dissipation in the External Loop Airlift Bioreactor (ELAB) used in this study, which causes the pressure difference method to be incorrect. On compare une méthode d'expansion de volume modifiée simple, ou méthode à tubes inclinés, à une méthode de différence de pression pour déterminer la rétention des gaz dans un bioréacteur à air ascendant. La méthode d'expansion de volume modifiée pourrait être utilisée pour tous les bioréacteurs pneumatiques oú la fluctuation du fluide est vigoureuse et l'observation visuelle de l'ascension de la phase continue difficile. Les données globales de rétention de gaz mesurées à l'aide de la méthode à tubes inclinés s'avèrent très proches de la rétention de gaz globale déterminéd à l'aide d'un moniteur de densité à rayons gamma. Toutefois, on a trouvé que la rétention de gaz globale mesurée par la méthode de différence de pression était significativement différente. Cette différence est due à la dissipation d'énergie dans le bioréacteur à air ascendant à boucle externe (ELAB) utilisé dans I'étude, qui rend la méthode de différence de pression incorrecte. [source]

Continuous bioremediation of phenol-polluted air in an external loop airlift bioreactor with a packed bed,

JOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 6 2006
Hossein Nikakhtari
Abstract An external loop airlift bioreactor with a small amount (99% porosity) of stainless steel mesh packing inserted in the riser section was used for bioremediation of a phenol-polluted air stream. The packing enhanced volatile organic chemical and oxygen mass transfer rates and provided a large surface area for cell immobilization. Using a pure strain of Pseudomonas putida, fed-batch and continuous runs at three different dilution rates were completed with phenol in the polluted air as the only source of growth substrate. 100% phenol removal was achieved at phenol loading rates up to 33 120 mg h,1 m,3 using only one-third of the column, superior to any previously reported biodegradation rates of phenol-polluted air with 100% efficiency. A mathematical model has been developed and is shown to accurately predict the transient and steady-state data. Copyright © 2006 Society of Chemical Industry [source]

Hydrodynamic considerations on optimal design of a three-phase airlift bioreactor with high solids loading

JOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 9 2003
Jaroslav Klein
Abstract The hydrodynamic study of a three-phase airlift (TPAL) bioreactor with an enlarged gas,liquid dual separator was carried out. Different lengths and diameters of the draft tube were tested to show how the design of the separator zone affects the hydrodynamic performance of the TPAL reactor. Ca-alginate beads with entrapped yeast biomass at different loadings (0, 7, 14 and 21% v/v) were used in order to mimic the solid phase of conventional high cell density systems, such as those with cells immobilized on carriers or flocculating cells. Important information on multiphase flow and distribution of gas and solid phases in the internal-loop airlift reactor (ALR) with high solids loading was obtained, which can be used for suggesting optimal hydrodynamic conditions in a TPAL bioreactor with high solids loading. It is finally suggested that the ALR with a dual separator and a downcomer to riser cross-sectional area ratio (AD/AR) ranging from 1.2 to 2.0 can be successfully applied to batch/continuous high cell density systems, where the uniform distribution of solid phase, its efficient separation of particles from the liquid phase, and an improved residence time of air bubbles inside the reactor are desirable. Copyright © 2003 Society of Chemical Industry [source]

Extractive bioconversion in a four-phase external-loop airlift bioreactor

AICHE JOURNAL, Issue 7 2000
Lidija Sajc
The integration of biosynthesis and product separation can increase the productivity of immobilized plant cells in airlift bioreactors. Extractive bioconversion of anthraquinones was studied in an external-loop airlift bioreactor consisting of a riser, a downcomer, and two horizontal sections, while containing alginate-immobilized Frangula alnus cells, a continuous aqueous phase (nutrient solution), dispersed solvent phase (n-hexadecane or silicone oil), and gas bubbles. A simple mathematical model was developed to describe the cocurrent liquid-liquid extraction in the riser section of the bioreactor and to rationalize the measured product concentrations in the aqueous and solvent phase. The model equations were solved analytically in a dimensionless form and used to study the effects of flow conditions, solvent properties, product formation rate, droplet size, and contactor length on the extraction efficiency and product concentration profiles in the continuous and dispersed phase. [source]

Modified volume expansion method for measuring gas holdup

Process modeling of in situ-adsorption of a bacterial lipase

BIOTECHNOLOGY & BIOENGINEERING, Issue 6 2005
Marcus Millitzer
Abstract In situ adsorption, known as an in situ-roduct removal (ISPR) technique for low molecular mass bioproducts, was in this study applied to a bacterial exoenzyme proving that this method is also suitable for the separation of macromolecules like proteins. For this, adsorbent particles were added to growing cultures of Staphylococcus carnosusrec., therefore both production and adsorption occurred simultaneously in shaking flasks, stirred tank, or airlift bioreactor as the chosen types of fermenters. The exoenzyme lipase adsorbed rapidly and, after separating cells and adsorbents, desorbed in a packed bed column. Up to 85% of the produced lipase were recovered, fractions of these had been concentrated up to the factor 20 and purified up to a factor of 40 by the procedure. By using the airlift bioreactor an enhancement of biomass production was observed, but the necessity of the addition of an anti-foam reagent resulted in higher product losses in adsorption as well as in desorption. Production and adsorption kinetics have been modeled and applied to in situ-adsorption. The model was used to perform a parameter study in which the influence of biological and physical parameters as well as process parameters on discontinuous and continuous in situ-adsorption was investigated. © 2005 Wiley Periodicals, Inc. [source]

Highly efficient strategy for enhancing taxoid production by repeated elicitation with a newly synthesized jasmonate in fed-batch cultivation of Taxus chinensis cells

BIOTECHNOLOGY & BIOENGINEERING, Issue 4 2005
Zhi-Gang Qian
Abstract A highly efficient bioprocessing strategy was developed for enhancing the production of plant secondary metabolites by repeatedly eliciting a fed-batch culture with a newly synthesized powerful jasmonate analog, 2,3-dihydroxypropyl jasmonate (DHPJA). In suspension cultures of a high taxuyunnanine C (Tc)-producing cell line of Taxus chinensis, 100 ,M DHPJA was added on day 7 to fed-batch cultures with feeding of 20 g L,1 sucrose on the same day. The synergistic effect of elicitation and substrate feeding on Tc biosynthesis was observed, which resulted in higher Tc accumulation than that by elicitation or sucrose feeding alone. More interestingly, both specific Tc yield (i.e., Tc content) and volumetric yield was further improved by a second addition of 100 ,M DHPJA (on day 12) to the fed-batch cultures. In particular, with repeated elicitation and sucrose feeding the Tc volumetric yield was increased to 827 ± 29 mg L,1, which was 5.4-fold higher than that of the nonelicited batch culture. Furthermore, the above novel strategy was successfully applied from shake flask to a 1-L airlift bioreactor. A high Tc production and productivity of 738 ± 41 mg L,1 and 33.2 ± 1.9 mg L,1 d,1, respectively, was achieved, which is higher than previous reports on Tc production in bioreactors. The results suggest that the aforementioned bioprocessing strategy may potentially be applied to other cell culture systems for efficient production of plant secondary metabolites. © 2005 Wiley Periodicals, Inc. [source]

A multikinetic model approach to predict gluconic acid production in an airlift bioreactor

BIOTECHNOLOGY JOURNAL, Issue 5 2007
Mukesh Mayani
Abstract This paper uses a multikinetic approach to predict gluconic acid (GA) production performance in a 4.5 L airlift bioreactor (ALBR). The mathematical model consists of a set of simultaneous firstorder ordinary differential equations obtained from material balances of cell biomass, GA, glucose, and dissolved oxygen. Multikinetic models, namely, logistic and contois equations constitute kinetic part of the main model. The main model also takes into account the hydrodynamic and mass transfer parameters. These equations were solved using ODE solver of MATLAB v6.5 software. The mathematical model was validated with the experimental data available in the literature and is used to predict the effect of change in initial biomass and air sparging rate on the GA production. It is concluded that the mathematical model incorporated with multikinetic approach would be more efficient to predict the change in operating parameters on overall bioprocess of GA production in an ALBR. [source]

Modelling of the fluid dynamic processes in a high-recirculation airlift reactor

INTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 6 2001
David A. Sanders
Abstract This paper describes the creation of two models of the steady-state fluid dynamic processes occurring in a high-recirculation airlift reactor. The new models were created to provide information to assist in the design of a reactor, in particular considering the selection of parameters to adjust in order to achieve a steady state solution. The modelling of two-phase flow of air and water in small-scale airlift bioreactors is considered. This modelling was applied to the high-recirculation airlift reactor process. New computer simulations were created and tests performed to evaluate the new models. The results of this evaluation are presented. The evaluation showed that variation of the superficial gas velocity or the simultaneous variation of the downcomer and riser diameters could be used to produce a steady-state design solution. Copyright © 2001 John Wiley & Sons, Ltd. [source]

Extractive bioconversion in a four-phase external-loop airlift bioreactor

Axial Distribution of Oxygen Concentration in Different Airlift Bioreactor Scales: Mathematical Modeling and Simulation

CHEMICAL ENGINEERING & TECHNOLOGY (CET), Issue 9 2006
H. Znad
Abstract Steady and unsteady state oxygen concentration distributions in the liquid and gas phases along the axial direction of different airlift bioreactor scales have been simulated for various gas flow rates and oxygen consumption rates by applying the axial dispersion model to the riser and the downcomer, and a complete mixing model for the top (separator) and the bottom sections of the bioreactor. The results show that the dissolved oxygen concentration is very low at the lower part of the downcomer when the rate of oxygen consumption by microorganisms is very high. Furthermore, the shorter (small) bioreactor shows relatively more uniform axial dissolved oxygen concentrations than the longer (large) bioreactor, due to the effect of the hydrostatic pressure along the bioreactor. One of the most important geometric factors for mass transfer is the reactor height, which dominates the mean pressure and thus influences the saturation concentration and mass transfer driving force. The presented model can be applied for modeling and scale-up of practical airlift bioreactors. [source]