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Yusuf Chisti - One of the best experts on this subject based on the ideXlab platform.

  • Elsevier Science B.V. Short Review
    2015
    Co-Authors: Murray Moo-young, Yusuf Chisti
    Abstract:

    An overview of bioreactor applications in treatment of gaseous, liquid and solid wastes is presented with emphasis on newer technologies. Waste treatment is considered in a broad context including concentration by bioaccumulation, degradation to substances with reduced environmental impact and upgrading to such useful products as feeds, foods and fuels. Biofilters and bioscrubbers for gas-eous pollutants, high-rate municipal and industrial wastewater treatment in Airlift Bioreactors, reac-tor-based soil bioremediation, artificial wetland filters for liquid effluents, and protein enrichment of agricultural solid residues are some of the technologies reviewed. The various treatment strategies are illustrated with examples. The developments discussed point to an increasing role for bioreaetor based processes in waste treatment and reuse

  • Oxygen transfer and mixing in mechanically agitated Airlift Bioreactors
    Biochemical Engineering Journal, 2002
    Co-Authors: Yusuf Chisti, Ulises Jáuregui-haza
    Abstract:

    Gas holdup, mixing, liquid circulation and gas–liquid oxygen transfer were characterized in a large ( ∼1.5 m 3 ) draft-tube Airlift bioreactor agitated with Prochem ® hydrofoil impellers placed in the draft-tube. Measurements were made in water and in cellulose fiber slurries that resembled broths of mycelial microfungi. Use of mechanical agitation generally enhanced mixing performance and the oxygen transfer capability relative to when mechanical agitation was not used; however, the oxygen transfer efficiency was reduced by mechanical agitation. The overall volumetric gas–liquid mass transfer coefficient declined with the increasing concentration of the cellulose fiber solids; however, the mixing time in these strongly shear thinning slurries was independent of the solids contents (0–4% w/v). Surface aeration never contributed more than 12% to the total mass transfer in air–water. © 2002 Elsevier Science B.V. All rights reserved.

  • axial inhomogeneities in steady state dissolved oxygen in Airlift Bioreactors predictive models
    Chemical Engineering Journal, 2001
    Co-Authors: Fernando Camacho Rubio, Jose Luis Garcia, E Molina, Yusuf Chisti
    Abstract:

    Models were developed for prediction and interpretation of the observed steady-state axial dissolved oxygen concentration profiles in tall Airlift Bioreactors. The observed concentration profiles were non-linear because of a combination of hydrodynamic and mass transport factors. The profiles were influenced mainly by the liquid-phase axial dispersion coefficient, the volumetric overall gas–liquid mass transfer coefficient, the gas velocity, the induced liquid circulation velocity. The model-predicted concentration profiles agreed within ±2% with the measured data in a tall (working aspect ratio ∼ 15) Airlift vessel operated under aeration regimens that are typically used during wastewater treatment. Axial inhomogeneities in dissolved oxygen increased with increasing aeration rate. This phenomenon may influence activated sludge processes in Airlift and deep-shaft reactors. The maximum attainable concentration of dissolved oxygen at the bottom of a typically aerated Airlift reactor, ≥ 3.5 m deep, always remained at 10% axially up the reactor. © 2001 Elsevier Science B.V. All rights reserved.

  • pneumatically agitated Bioreactors in industrial and environmental bioprocessing hydrodynamics hydraulics and transport phenomena
    Applied Mechanics Reviews, 1998
    Co-Authors: Yusuf Chisti
    Abstract:

    Major aspects of design and operation of pneumatically agitated Bioreactors are reviewed. The focus is on considerations that are relevant to industrial practice. Airlift Bioreactors are emphasized. The treatment covers hydraulics, hydrodynamics, gas-liquid and solid-liquid mass transfer, heat transfer, mixing, and suspension. Newtonian and non-Newtonian systems are discussed. Applications in microbial fermentations, animal and plant cell culture, biotransformations with immobilized enzymes, and treatment of wastewater are outlined. Comparisons with more conventional bioreactor technologies are made. Design features for sterile processing in Airlift systems are detailed. The evidence for superior performance of Airlift Bioreactors is overwhelming. Excellent productivities have been demonstrated with yeasts, bacteria, and filamentous fungi. Processes that produce highly viscous broths, including several biopolymer producing fermentations, have been proven in Airlift devices. Similarly, many hybridoma cultures and plant cell suspensions have given good results. As a general rule, volumetric productivity of Airlift Bioreactors equals or betters that of conventional stirred tanks. Typically, this level of performance is achieved at substantially lower power input than in stirred vessels. Furthermore, the probability of mechanical failure and likelihood of loss of sterility are lower with Airlift Bioreactors. In wastewater treatment, too, Airlift devices have far outperformed conventional systems. Airlift Bioreactors accept higher BOD loadings, produce less sludge, and the degradation rate is faster; performance improves with increasing scale of operation. This review article includes 328 references.

  • Characterization of shear rates in Airlift Bioreactors for animal cell culture
    Journal of Biotechnology, 1997
    Co-Authors: Emilio Molina Grima, Yusuf Chisti, Murray Moo-young
    Abstract:

    Abstract A well established analysis of energy dissipation in the riser, downcomer and the bottom sections of split-cylinder Airlift Bioreactors (aspect ratio=7.6 and 14.5; equal riser-to-downcomer cross-sectional area ratios of 1.0) was used to characterize shear rates in those systems for application to animal cell culture. Shear rates were evaluated for suspensions of typical microcarriers (loading =0–30 kg m −3 ; particle diameter=(150–300)×10 −6 m; density 1030–1050 kg m −3 ) encountered in anchorage-dependent cell culture and for microcarrier-free liquids. For the reactors tested, the highest shear rates were encountered in the bottom zone; the riser had lower shear rate values, while the downcomer was the most quiescent. The shear rates in various zones ranged over 0–12 000 s −1 for a riser superficial gas velocity range of 0–6.7×10 −3 m s −1 which is typical for cell culture. In all zones, the shear rates increased with increasing aeration rate. Shear rates declined with increasing loading of microcarriers, but were not substantially affected by the carrier diameter or density. Relative to the microcarrier free system, even small amounts of carriers (6 kg m −3 ) lowered the maximum prevailing shear rate to about 4000 s −1 . The shear rates were extremely sensitive to the length scale of the fluid eddies when the eddy length-to-carrier diameter ratio was less than or equal to unity. The results showed quantitatively how the shear rate in various zones of Airlift reactors may be manipulated by modifications to operational and geometric parameters. The methodology presented allowed for characterization of shear rates in the bulk flow, unlike existing studies that provide information only on wall shear rates which are not particularly relevant to shear sensitive bioprocesses.

Yoshinori Kawase - One of the best experts on this subject based on the ideXlab platform.

  • Heat transfer in bubble column and Airlift Bioreactors: Newtonian and non-Newtonian fermentation broths.
    Journal of chemical technology and biotechnology (Oxford Oxfordshire : 1986), 2007
    Co-Authors: Yoshinori Kawase, Takahiro Kumagai
    Abstract:

    A theoretical model has been developed for heat transfer in bubble column and Airlift Bioreactors, which is applicable for Newtonian and non-Newtonian fermentation media. The proposed model is based on a similarity between heat transfer in gas-sparged pneumatic reactors and turbulent natural convection. The applicability of the proposed model was discussed using a wide range of experimental data, and good agreement was obtained.

  • Modeling and simulation of Airlift Bioreactors
    Biochemical Engineering Journal, 2004
    Co-Authors: Hussein Znad, V. Baleš, Jozef Markoš, Yoshinori Kawase
    Abstract:

    Abstract A tanks-in-series model was applied for mathematical modeling of the unsteady state performance of a semi batch operation in a 10.5 dm 3 internal loop Airlift bioreactor for the production of gluconic acid by fermentation. A set of first order differential equations for the material balances of micro-organism, substrate, product, and dissolved oxygen around the hypothetical well mixed stages in the riser and the downcomer was solved simultaneously using the Athena software package. The kinetic model used considers the effect of two substrates (glucose and dissolved oxygen) on the growth rate. Both the effect of airflow rate and the height of the Airlift bioreactor on the gluconic acid production were investigated. The model has been validated with experimental data. The model is simple enough to be used in design studies and it can be adapted to Airlift system configurations and fermentation systems other than gluconic acid fermentation.

  • Dynamic modeling and simulation of continuous Airlift Bioreactors
    Bioprocess Engineering, 2000
    Co-Authors: T. Kanai, J. Ichikawa, H. Yoshikawa, Yoshinori Kawase
    Abstract:

    For dynamic behaviors of continuous Airlift Bioreactors, a mathematical model based on a tanks-in-series model with backflow has been developed. The equations describing the dynamics of Airlift Bioreactors are material balances for micro-organism, substrate, dissolved oxygen and oxygen in gas-phase and heat balances. Non-ideal mixing of liquid and gas phases is taken into account using a tanks-in-series model with backflow. The batch operation, startup operation and the consequence of plant failure were simulated and the effects of design and operating parameters for an Airlift bioreactor on its dynamic behaviors were discussed. The concentration profiles of micro-organism, substrate, dissolved oxygen and oxygen in gas-phase and the temperature profile in an Airlift Bioreactors and their dynamics were obtained. The computational results indicate that the transients of a chemostat in the case of bubble column bioreactor are slower compared with those in the case of Airlift bioreactor. The proposed simulator is more precise as compared with models published previously in the literature and therefore provides more reliable and rational examination of continuous Airlift bioreactor performance.

  • Gas hold-up and oxygen transfer in three-phase external-loop Airlift Bioreactors : Non-Newtonian fermentation broths
    Journal of Chemical Technology & Biotechnology, 1996
    Co-Authors: Yoshinori Kawase, Norihisa Hashimoto
    Abstract:

    The effects of solids loading on gas hold-up and oxygen transfer in external-loop Airlift Bioreactors with non-Newtonian fermentation media are discussed. Experiments were performed in two model external-loop Airlift Bioreactors with aqueous solutions of carboxymethyl cellulose (CMC) and xanthan gum representing non-Newtonian flows. Low-density plastic particles of 1030 and 1300 kg m -3 were used and the solids loading was varied in the range 0-20% (v/v). For the inelastic non-Newtonian CMC aqueous solutions, the presence of low-density solid particles slightly increased the riser gas hold-up, Φ gr , but decreased the volumetric mass transfer coefficient, k L a. On the other hand, Φ gr decreased but k L a increased with solids loading in the viscoelastic non-Newtonian xanthan gum aqueous solution. The extent of these effects depended on non-Newtonian flow behavior. Theoretical models of riser gas hold-up and volumetric mass transfer coefficient have been developed. The capability of the proposed models was examined using the present experimental data obtained in the model external-loop Airlift Bioreactors and the available data in the literature. The data were successfully correlated by the proposed correlations except the results for k L a coefficient in the xanthan gum solution.

  • Simulation of Airlift Bioreactors: Steady-state performance of continuous culture processes
    Computers & Chemical Engineering, 1996
    Co-Authors: T. Kanai, T. Uzumaki, Yoshinori Kawase
    Abstract:

    A tanks-in-series model was applied for mathematical modeling of the steady-state performance of continuous cultures in an Airlift bioreactor. In the present computational algorithm, non-linear algebraic equations for the material balances of micro-organism, substrate and dissolved oxygen around the hypothetical well-mixed stages with backflow in the riser and downcomer were solved simultaneously using the Newton-Raphson technique. The concentration profiles of micro-organism, substrate and dissolved oxygen in the Airlift bioreactor for continuous cultures were obtained under the same specifications. The simulation results were discussed mainly from the viewpoint of mixing in the Airlift bioreactor. The relationships between the micro-organism productivity and design parameters of the Airlift bioreactor such as liquid recycle flow rate and downcomer configuration were examined. The effect of mixing on the washout was also discussed. Numerical examples indicate that the proposed simulation scheme is very flexible and useful for the design and operation studies of Airlift Bioreactors.

R Z Tudose - One of the best experts on this subject based on the ideXlab platform.

  • Stochastic modelling of axial dispersion in external-loop Airlift Bioreactors
    Bioprocess Engineering, 2000
    Co-Authors: Maria Gavrilescu, O. Muntean, R Z Tudose
    Abstract:

    The paper presents a model of the motion of a particle subjected to several transport processes in connection with mixing in two phase flow. A residence time distribution technique coupled with a one-dimensional dispersion model was used to obtain the axial dispersion coefficient in the liquid phase, Dax. The proposed model of Dax for an external-loop Airlift bioreactor is based on the stochastic analysis of the two-phase flow in a cocurrent bubble column and modified for the specific flow in the Airlift reactor. The model takes into account the riser gas superficial velocity, the riser liquid superficial velocity, the Sauter bubble diameter, the riser gas hold-up, the downcomer-to-riser cross sectional area ratio. The proposed model can be applied with an average error of ±20.

  • Modelling mixing parameters in concentric-tube Airlift Bioreactors
    Bioprocess Engineering, 1999
    Co-Authors: Maria Gavrilescu, R Z Tudose
    Abstract:

    Axial dispersion of the liquid phase was investigated in a concentric-tube Airlift bioreactor (RIMP: VL=0.70 m3) as a whole and in the separate zones (riser, downcomer, gas-separator) using the axial dispersion model. The axial dispersion number Bo and the axial dispersion coefficient, Dax were determined from the output curves to an initial Dirac pulse, using the tracer response technique. They were analyzed in relation to process and geometrical parameters, such as: gas superficial velocity, νSGR; top clearance, hS; bottom clearance, hB, and resistances at downcomer entrance expressed as Ad/AR ratio. Correlations between Bodenstein numbers in the overall bioreactor and riser and downcomer sections (BoT,BoR,BoD) and the geometrical and process parameters were developed, which can allow to assess the complex influence of these parameters on liquid axial dispersion.

  • modelling mixing parameters in concentric tube Airlift Bioreactors part ii axial dispersion
    Bioprocess Engineering, 1999
    Co-Authors: Maria Gavrilescu, R Z Tudose
    Abstract:

    Axial dispersion of the liquid phase was investigated in a concentric-tube Airlift bioreactor (RIMP: V L = 0.70 m 3 ) as a whole and in the separate zones (riser, downcomer, gas-separator) using the axial dispersion model. The axial dispersion number Bo and the axial dispersion coefficient, D ax were determined from the output curves to an initial Dirac pulse, using the tracer response technique. They were analyzed in relation to process and geometrical parameters, such as: gas superficial velocity, υ SGR ; top clearance, h S ; bottom clearance, h B : and resistances at downcomer entrance expressed as A d /A R ratio. Correlations between Bodenstein numbers in the overall bioreactor and riser and downcomer sections (Bo T , Bo R . Bo D ) and the geometrical and process parameters were developed, which can allow to assess the complex influence of these parameters on liquid axial dispersion.

  • concentric tube Airlift Bioreactors part i effects of geometry on gas holdup
    Bioprocess Engineering, 1998
    Co-Authors: Maria Gavrilescu, R Z Tudose
    Abstract:

    Gas holdup investigations were performed in three concentric-tube Airlift reactors of different scales of operation (RIMP: 0.070 m3; RIS-1: 2.5 m3; RIS-2: 5.2 m3; nominal volumes). The influences of the top and bottom clearances and the flow resistances at the downcomer entrance were studied using tap water as liquid phase and air as gaseous phase, at atmospheric pressure. It was found that the gas holdup in the individual zone of the reactor: riser, downcomer and gas-separator, as well as that in the overall reactor is affected by the analyzed geometrical parameters in different ways, depending on their effects on liquid circulation velocity. Gas holdup was satisfactorily correlated with Fr, Ga, bottom spatial ratio (B), top spatial ratio (T), gas separation ratio (Y) and downcomer flow resistance ratio (A d /A R ). Correlations are presented for gas holdup in riser, downcomer, gas separator and for the total gas holdup in the reactor. All the above stressed the importance of the geometry in dynamic behaviour of Airlift reactors.

  • Hydrodynamics of non-Newtonian liquids in external-loop Airlift Bioreactors. Part 2 : Study of the liquid circulation velocity
    Bioprocess Engineering, 1998
    Co-Authors: Maria Gavrilescu, R Z Tudose
    Abstract:

    In order to obtain further information on the behaviour and optimal design of external-circulation-loop Airlift Bioreactors, the liquid circulating velocity was studied using highly viscous pseudoplastic solutions of starch and antibiotic biosynthesis liquids of Penicillium chrysogenum, Streptomyces griseus, Streptomyces erythreus, Bacillus licheniformis and Cephalosporium acremonium. Measurements of liquid circulation velocity were made in laboratory and pilot plant external-loop Airlift Bioreactors, under various conditions concerning gas flow rate, riser liquid height at constant downcomer height, A D /A R ratio, using the impulse-response technique. It has been found that these parameters had a significant effect on liquid circulation velocity together with the apparent viscosity and dry weight of the solid phase in the biosynthesis liquids. For the tested liquids, the superficial liquid velocity in the riser section of an external-loop Airlift bioreactor may be described by the following equation: V SLR = CV SGR a (A D /A R ) b (H s /H D ) C (η ap /η W ) d C e s , where the exponents and the constant c take different values depending on the liquid phase properties and flow regime.

Rubens Maciel Filho - One of the best experts on this subject based on the ideXlab platform.

  • hydrodynamics and mass transfer in bubble column conventional Airlift stirred Airlift and stirred tank Bioreactors using viscous fluid a comparative study
    Biochemical Engineering Journal, 2017
    Co-Authors: Sérgio S. De Jesus, João Moreira Neto, Rubens Maciel Filho
    Abstract:

    Abstract The performance of four Bioreactors (bubble column, concentric tube Airlift, concentric tube stirred Airlift, and mechanically stirred tank) were evaluated in this study in terms of the hydrodynamics and mass transfer, using viscous a Newtonian fluid (glycerol 65%) and a non-Newtonian fluid (xanthan 0.25%). The experimental results showed that the gas holdup and mass transfer coefficient were higher in the stirred Airlift and stirred tank, on the other hand these reactors had high shear rates. In relation to power consumption, lower values were obtained in the bubble column and Airlift Bioreactors. In a viscous medium in which microorganisms or shear-sensitive cells are used, the use of Airlift Bioreactors may be the best choice for presenting a low shear environment and a reasonable oxygen transfer rate, in addition to the low power consumption. On the other hand, if the process involves microorganisms that require high oxygen rates, a stirred Airlift bioreactor may be the best choice.

  • Influence of impeller type on hydrodynamics and gas‐liquid mass‐transfer in stirred Airlift bioreactor
    AIChE Journal, 2015
    Co-Authors: Sérgio S. De Jesus, João Moreira Neto, Aline Santana, Rubens Maciel Filho
    Abstract:

    The influence of impeller type in a mechanically stirred Airlift bioreactor was analyzed in relation to the non-Newtonian viscous fluids. The agitation was carried out through a marine impeller (axial impeller) and a paddle impeller (radial impeller) located along with the gas sparger in the region comprised by the riser. The bioreactor was sparged with air under different velocities (0.036–0.060 m s−1). Carboxymethylcellulose 1.94% and xanthan 1.80% were used as a fluid model. The gas holdup and volumetric mass-transfer coefficient increased in up to five and three times, respectively, when compared to a conventional Airlift bioreactor; however, better results were obtained when the straight paddle impeller type was used. The results suggest that the studied bioreactor can be used successfully in viscous fluid, and it can be more efficient than conventional Airlift Bioreactors. The results obtained suggest the use of radial impellers. © 2015 American Institute of Chemical Engineers AIChE J, 61: 3159–3171, 2015

Alberto C. Badino - One of the best experts on this subject based on the ideXlab platform.

  • Average shear rate in Airlift Bioreactors: searching for the true value
    Bioprocess and Biosystems Engineering, 2019
    Co-Authors: Mateus N. Esperança, Marcel Otavio Cerri, Caroline E. Mendes, Guilherme Y. Rodriguez, Rodrigo Béttega, Alberto C. Badino
    Abstract:

    The shear rate is an important bioreactor parameter that needs to be evaluated due to its impact on microorganism morphology and viability, and consequently on bioproduct formation. Airlift Bioreactors, classified as low-shear devices, are used as an alternative to conventional stirred-tank reactors. Considerable efforts have been made to characterize the shear environments in Airlift Bioreactors, using the average shear rate ( $${\dot {\gamma }_{{\text{av}}}}$$ γ ˙ av ) as a key parameter. However, there is no agreement among the values obtained in different studies, which can differ even in orders of magnitude. The methodologies used to obtain $${\dot {\gamma }_{{\text{av}}}}$$ γ ˙ av in the different studies could be the reason for the lack of agreement among them. In this work, $${\dot {\gamma }_{{\text{av}}}}$$ γ ˙ av in a concentric tube Airlift bioreactor was evaluated using computational fluid dynamics (CFD), as well as based on universal velocity profiles for liquid flows in smooth pipes and annuli. Good agreement was obtained between the CFD-based average shear rates and the values obtained from universal velocity profiles, indicating that CFD simulation is a valuable tool for $${\dot {\gamma }_{{\text{av}}}}$$ γ ˙ av prediction.

  • effect of geometric design on performance of square cross section concentric duct and split Airlift Bioreactors
    Canadian Journal of Chemical Engineering, 2017
    Co-Authors: Mateus N. Esperança, Rodrigo Béttega, Alberto C. Badino
    Abstract:

    The performance of internal-loop Airlift Bioreactors is affected by their geometry, especially the bottom and gas-liquid separator designs. Despite efforts to understand the impact of geometry on bioreactor hydrodynamics and oxygen transfer, the contribution of each region to the bioreactor performance as a whole has been evaluated separately. Consequently, it has not been possible to define the best overall geometry. This work discusses the influence of the bottom and gas-liquid separator geometries on the volumetric oxygen transfer coefficient (kLa) and superficial liquid circulation velocity (UL) of 10-L square cross-section concentric-duct Airlift (CDA) and split Airlift (SA) reactors. Both Airlift reactors were operated with distilled water and Saccharomyces cerevisiae cultivation broth. Based on the results it was possible to indicate the best geometric configurations for biotechnological applications. Gas-liquid separator design was evaluated by changing the openness angle (α) and the gas-liquid separator volumetric liquid fraction (FGLS), while the free area for liquid flow between riser and downcomer (Ab) was the geometric parameter modified for the bottom. The results showed that liquid circulation was strongly affected by the bottom geometry, considering the kLa values, while the gas-liquid separator significantly affected both variables. Combining the impacts of both regions, promising Airlift geometries were identified that exhibited low or high hydrodynamics and oxygen transfer levels. These findings highlight the flexibility of Airlift Bioreactors and provide information required for their design in order to satisfy specific requirements of different aerobic bioprocesses. This article is protected by copyright. All rights reserved

  • Oxygen transfer in three scales of concentric tube Airlift Bioreactors
    Biochemical Engineering Journal, 2010
    Co-Authors: Marcel Otavio Cerri, Alberto C. Badino
    Abstract:

    Abstract Oxygen transfer was evaluated in three internal-loop Airlift reactors (ALRs) of different working volumes (2, 5, and 10 dm3) and similar geometric configuration utilizing eight Newtonian and five non-Newtonian fluids. The effects of the superficial gas velocity (UGR) and liquid viscosity (μL) had opposite effects on the volumetric oxygen transfer coefficient (kLa). However, they presented the same orders of magnitude showing that the viscosity effect on oxygen mass transfer cannot be neglected. A correlation for kLa based on dimensional analysis considering the effects of the geometric parameters, the physical properties of the fluid, and the operational conditions presented a very good fitting to the experimental data. The correlation shows that the influence of the reactor internal diameter on kLa was considered positive. Therefore, in larger-scale reactors an appropriate oxygen transfer can be reached under smaller aeration conditions.