scholarly journals Optimization of the mixing in stirred bioreactors, 1. Comparative analysis of the mixing efficiency with different radial impellers for simulated broths

2007 ◽  
Vol 13 (1) ◽  
pp. 1-20 ◽  
Author(s):  
Dan Cascaval ◽  
Anca-Irina Galaction ◽  
Elena Folescu
Keyword(s):  
Mixing Time ◽  
Ph Sensor ◽  
Mixing Efficiency ◽  
Energetic Efficiency ◽  
Rushton Turbine ◽  
Stirred Bioreactor ◽  
Mixing Intensity ◽  
Bulk Volume ◽  
Shear Effects ◽  
Stirred Bioreactors

Although radial impellers, especially the Rushton turbine, are widely used in stirred bioreactors, their applicability is limited by the high apparent viscosities of the broth. Beside the intensification of broth circulation, the energetic efficiency and the shear effects on biocatalysts must be taken into account to select the optimum impeller or impellers combination. In this context, the paper presents a comparative study on the efficiency of seven different radial impellers for simulated broth mixing in a stirred bioreactor. The analysis was made by means of the mixing time values obtained by vertically changing the position of the pH-sensor in the broths, in correlation with the energy consumption needed for a certain level of mixing time or for the uniform distribution of the mixing intensity into the bulk volume of the broths.

scholarly journals Optimization of mixing in stirred bioreactors, 2: Selection of optimum impeller combinations for non-aerated simulated broths

2007 ◽  
Vol 13 (1) ◽  
pp. 21-26 ◽  
Author(s):  
Anca-Irina Galaction ◽  
Elena Folescu ◽  
Dan Cascaval
Keyword(s):  
Fermentation Broth ◽  
Mixing Time ◽  
Maximum Level ◽  
Specific Power ◽  
Mixing Efficiency ◽  
Mechanical Mixing ◽  
Rushton Turbine ◽  
Shear Effects ◽  
Stirred Bioreactors ◽  
Selection Of

Although radial impellers, especially the Rushton turbine, are widely used in stirred bioreactors, their applicability is limited by the high apparent viscosities of the broths. For optimizing mechanical mixing by selecting the appropriate impeller for a specific fermentation broth or process, the comparative analysis of the mixing efficiency, energy costs and shear effects on the biocatalysts is required. By means of this analysis, three different combinations of radial impellers for water and viscous simulated broths were selected for attaining optimum mixing in a bioreactor. The proposed impellers combinations offer the most intense and uniformly distributed mixing and the lowest specific power consumption required for reaching a maximum level of mixing time of less than one minute.

scholarly journals Modeling of mixing for stirred bioreactors: 3. Mixing time for aerated simulated broths

2002 ◽  
Vol 56 (12) ◽  
pp. 506-513 ◽  
Author(s):  
Dan Cascaval ◽  
Corneliu Oniscu ◽  
Anca-Irina Galaction ◽  
Fiorina Ungureanu
Keyword(s):  
Flow Rate ◽  
Rotation Speed ◽  
Mixing Time ◽  
Volumetric Flow Rate ◽  
Mixing Efficiency ◽  
Complex Flow ◽  
Average Deviation ◽  
Stirred Bioreactor ◽  
Stirred Bioreactors ◽  
Turbine Impeller

This paper presents the experiments on mixing efficiency for aerated media for a laboratory stirred bioreactor with a double turbine impeller. The effects of stirrer rotation speed, air volumetric flow rate and stirrer position on the shaft on mixing time for aerated water and simulated broths (CMCNa solutions) were analyzed. Compared to non-aerated broths, the results indicated that the variation of mixing time with the considered parameters is very different, due to the complex flow mechanism of the gas-liquid dispersion, a mechanism which is changed by changing the broth properties or fermentation conditions. Using the Statistics Toolbox of MATLAB some correlations between the mixing time and rotation speed, air volumetric flow rate and stirrer position on the shaft were established. The proposed equations agree well with the experiments, the average deviation being ?9.02%.

Hydrodynamics of Stirred Bioreactors

1998 ◽  
Vol 51 (1) ◽  
pp. 3-32 ◽  
Author(s):  
A. W. Nienow
Keyword(s):  
Energy Dissipation ◽  
Mixing Time ◽  
Scale Up ◽  
Axial Flow ◽  
High Viscosity ◽  
Flow Patterns ◽  
Rushton Turbine ◽  
Stirred Bioreactor ◽  
Power Characteristics ◽  
Stirred Bioreactors

This review of the hydrodynamics of stirred bioreactors begins with an introduction to the agitation problems of particular concern in such systems. This is followed by a brief review of some basic concepts in turbulence and rheology of relevance to bioreactors. Important aspects of single phase mixing in low viscosity, high viscosity and Theologically complex broths are then covered in some detail including flow patterns, power number versus Reynolds number plots (including the modification of the latter to allow for shear thinning broths), flow numbers, energy dissipation rates and flow close to impellers and between multiple impeller systems. From these basic principles, the problem of homogenization is then covered in depth because of its significance for bioreactor performance. Aeration concepts are then introduced and the behavior of traditional Rushton turbine impellers is then treated in detail, covering the flow patterns, aerated power characteristics, mixing time and scale-up considerations. The weaknesses of the Rushton turbine are then discussed which leads into a section describing how more modern impellers are able to improve on many of these, especially emphasising their ability to introduce more energy dissipation into the broth and handle more air before flooding, both of which enhance oxygen transfer. The improvement in bulk blending found with multiple axial flow agitators is brought out too. Finally, the retrofitting of fermenters originally containing Rushton turbines with these more modern impellers is discussed. In conclusion, it is clear that there have been substantial increases in the understanding of stirred bioreactor hydrodynamics. However, whilst further understanding will occur within the framework discussed here, the expectation must be that computational fluid dynamics will increase in importance in spite of the difficulty of handling complex rheology, multiphase systems and biological responses. This review article has 135 references.

scholarly journals Intensifying the Fermentation of Aspergillus oryzae in a Stirred Bioreactor Using Maxblend Impeller

2016 ◽  
Vol 10 (1) ◽  
pp. 88-109 ◽  
Author(s):  
Narges Ghobadi ◽  
Chiaki Ogino ◽  
Naoto Ohmura
Keyword(s):  
Growth Rate ◽  
Enzyme Activity ◽  
Power Consumption ◽  
Aspergillus Oryzae ◽  
Rushton Turbine ◽  
Stirred Bioreactor ◽  
Condition Effect ◽  
Batch Condition ◽  
Fermentation Parameters ◽  
Stirred Bioreactors

Background: The intensification of fermentation in stirred bioreactors is an attractive approach for commercial interests and industries that work with biochemical products. Alpha amylase is an enzymatic bio-products that is produced largely from Aspergillus oryzae. Using adaptable agitator can be an efficient way for stirred fermentation. Objective: This study, concentrated on enhancing the mixing process in order to intensify Aspergillus oryzae fermentation. A straight type of Maxblend® impeller was used as an agitator to investigate the incubation parameters compared with the use of a 6-blade double Rushton turbine. Method: Stirred fermentation was done in batch condition. Effect of flow pattern of mixing on fermentation parameters was investigated after each sampling. Results: The results showed that the Maxblend® significantly intensified both enzyme activity and growth rate at low and moderate rates of power consumption (P). The main reason for the decreases in the growth rate and the enzyme activity during agitation by the Rushton turbine at low and high Pv was the lack of oxygen and mycelial damage, respectively. Additionally, use of the Maxblend® significantly intensified the KLa at low and moderate rates of power consumption. Conclusion: Axial and uniform mixing by Maxblend® impeller was resulted in improving the fermentation characteristics and enzyme activity.

scholarly journals Comparative analysis of mixing efficiency and distribution induced by radial impellers in bioreactors with stirred bed of immobilized cells

2010 ◽  
Vol 16 (1) ◽  
pp. 47-64
Author(s):  
Anca-Irina Galaction ◽  
Anca-Marcela Lupăşteanu ◽  
Marius Turnea ◽  
Dan Caşcaval
Keyword(s):  
Experimental Data ◽  
Comparative Analysis ◽  
Immobilized Cells ◽  
Mixing Time ◽  
Mixing Efficiency ◽  
Rushton Turbine ◽  
Mobile Bed ◽  
Main Factors ◽  
Good Concordance

The influences of the main factors on the mixing efficiency and distribution for a bioreactor with stirred/mobile bed of immobilized S. cerevisiae cells in alginate (biocatalyst particles with 4, 4.6 and 5.2 mm diameters) have been comparatively analyzed for six radial impellers: a disperser sawtooth, Smith turbine, a pumper mixer, a curved bladed turbine, a paddle with six blades, a pitched bladed turbine vs. Rushton turbine. The most efficient impellers, from the viewpoint of intensity and uniformity of the suspension circulation were found to be the Smith turbine, the paddle with six blades and the pitched bladed turbine. The mathematical correlations describing the influence of the main factors on mixing time were established for each studied impeller offering a good concordance with the experimental data (the average deviations vary from ?7.9% for pitched bladed turbine to ?12.1% for disperser sawtooth).

scholarly journals CFD simulation of the hydrodynamics and mixing time in a stirred tank

2010 ◽  
Vol 16 (4) ◽  
pp. 379-386 ◽  
Author(s):  
Aoyi Ochieng ◽  
Maurice Onyango
Keyword(s):  
Cfd Simulation ◽  
Draft Tube ◽  
Mixing Time ◽  
Operating Cost ◽  
Flow Fields ◽  
Stirred Tank ◽  
Mixing Efficiency ◽  
Phase System ◽  
Rushton Turbine ◽  
Power Draw

Hydrodynamics and mixing efficiency in stirred tanks influence power draw and are therefore important for the design of many industrial processes. In the present study, both experimental and simulation methods were employed to determine the flow fields in different mixing tank configurations in single phase system. The laser Doppler velocimetry (LDV) and computational fluid dynamics (CFD) techniques were used to determine the flow fields in systems with and without a draft tube. There was a reasonable agreement between the simulation and experimental results. It was shown that the use of a draft tube with the Rushton turbine and hydrofoil impeller resulted in a reduction in the homogenization energy by 19.2% and 17.7%, respectively. This indicates that a reduction in the operating cost can be achieved with the use of a draft tube in a stirred tank and there would be a greater cost reduction in a system stirred by the Rushton turbine compared to that stirred by a propeller.

scholarly journals Modeling of mixing in stirred bioreactors 4. mixing time for aerated bacteria, yeasts and fungus broths

2004 ◽  
Vol 58 (3) ◽  
pp. 128-137 ◽  
Author(s):  
Dan Cascaval ◽  
Anca-Irina Galaction ◽  
Corneliu Oniscu ◽  
Florina Ungureanu
Keyword(s):  
Experimental Data ◽  
Mixing Time ◽  
Biomass Concentration ◽  
Aeration Rate ◽  
Mixing Efficiency ◽  
Complex Flow ◽  
Average Deviation ◽  
Stirred Bioreactors ◽  
Turbine Impeller ◽  
Good Agreement

The mixing time for bioreactors depends mainly on the rheoiogicai properties of the broths, the biomass concentration and morphology, mixing system characteristics and fermentation conditions. For quantifying the influence of these factors on the mixing efficiency for stirred bioreactors, aerated broths of bacteria (P. shermanii), yeasts (S. cerevisiae) and fungi (P. chrysogenum, free mycelia and mycelial aggregates) of different concentrations have been investigated using a laboratory bioreactor with a double turbine impeller. The experimental data indicated that the influence of the rotation speed, aeration rate and stirrer positions on the mixing intensity strongly differ from one system to another and must be correlated with the microorganism characteristics, namely: the biomass concentration and morphology. Moreover, compared with non-aerated broths, variations of the mixing time with the considered parameters are very different, due to the complex flow mechanism of gas-liquid dispersions. By means of the experimental data and using a multiregression analysis method some mathematical correlations for the mixing time of the general form: tm = a1*Cx2+a2*Cx+a3*IgVa+a4-N2+a5-N+a6/a7*L2+a8*L+a9 were established. The proposed equations offer good agreement with the experiments, the average deviation being ?6.7% - ?9.4 and are adequate for the flow regime Re < 25,000.

CFD Analysis and Design Optimization in a Curved Blade Impeller

2017 ◽  
Vol 15 (1) ◽  
Author(s):  
Nazila Sutudehnezhad ◽  
Ramin Zadghaffari
Keyword(s):  
Flow Field ◽  
Mixing Time ◽  
Computational Method ◽  
Stirred Tank ◽  
Mixing Efficiency ◽  
Rushton Turbine ◽  
Stirred Tank Reactors ◽  
Analysis And Design ◽  
Curved Blade ◽  
Reported Data

Abstract Mixing efficiency in stirred tank reactors is an important challenge in the design of many industrial processes. The effect of blade shape on mixing efficiency has been studied in the present work. The computational method has been used to investigate the flow field, power consumption, pumping capacity, hydraulic efficiency, and mixing time in a fully baffled tank stirred by a Rushton turbine and different curved blade impellers. Flow in a stirred tank reactor involves interactions between flow around rotating blades and stationary baffles. The flow field was developed using the sliding mesh (SM) approach in computational fluid dynamics (CFD). The realizable k-ε was used to model the turbulence. A reasonable agreement between the experimental reported data and simulation results indicated the validity of CFD model. It has been revealed that increasing the blade curvature, at approximately the same mixing time would enhance the mixing efficiency up to 61.3 % in comparison with the Rushton turbine. This mixing efficiency would favor the employment of curved blade impellers due to the cost-benefits of stirred tank operations.

scholarly journals Core–shell hydrogel microcapsules enable formation of human pluripotent stem cell spheroids and their cultivation in a stirred bioreactor

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Pouria Fattahi ◽  
Ali Rahimian ◽  
Michael Q. Slama ◽  
Kihak Gwon ◽  
Alan M. Gonzalez-Suarez ◽  
...  
Keyword(s):  
Stem Cells ◽  
Stem Cell ◽  
Scale Up ◽  
Bioreactor Culture ◽  
Stirred Bioreactor ◽  
Cell Spheroids ◽  
Poly Ethylene ◽  
Aqueous Core ◽  
End Stage ◽  
Stirred Bioreactors

AbstractCellular therapies based on human pluripotent stem cells (hPSCs) offer considerable promise for treating numerous diseases including diabetes and end stage liver failure. Stem cell spheroids may be cultured in stirred bioreactors to scale up cell production to cell numbers relevant for use in humans. Despite significant progress in bioreactor culture of stem cells, areas for improvement remain. In this study, we demonstrate that microfluidic encapsulation of hPSCs and formation of spheroids. A co-axial droplet microfluidic device was used to fabricate 400 μm diameter capsules with a poly(ethylene glycol) hydrogel shell and an aqueous core. Spheroid formation was demonstrated for three hPSC lines to highlight broad utility of this encapsulation technology. In-capsule differentiation of stem cell spheroids into pancreatic β-cells in suspension culture was also demonstrated.

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