The Experts below are selected from a list of 87 Experts worldwide ranked by ideXlab platform
Shijie Liu - One of the best experts on this subject based on the ideXlab platform.
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Bioreactor Design Operation
Bioprocess Engineering, 2017Co-Authors: Shijie LiuAbstract:For a well-mixed reactor, there are three common operational modes: batch, steady CSTR, and fed-batch. Batch operation has the best flexibility, while CSTR has the highest productivity. There are three basic reactor types for aerobic cultivation of suspended cells: internal mixing; bubble columns; and loop reactors, each with different properties. Scale-up is difficult because conditions in a large vessel are more heterogeneous than in a small vessel; scale-up problems are all related to transport processes. Scale-down techniques are useful in identifying the controlling regime at the smaller scale, where many parameters can be tested more quickly and less expensively than at the production scale. Bioreactor instrumentation and control are important for bioreactor operations. Improvements in sensor technology and the dynamical models of bioreactors are critical to improvements in control technology. Sterilization is the removal of biocontaminants or foreign organisms for a fermentation system and the surrounding equipment. Industrial fermenters and associated pipings are designed for in situ steam sterilization under pressure, or steam in place. The use of saturated steam is common and advantageous over other hot fluids. Stringent requirement leads to longer reduced sterilization time, t S . Bacterial spores are known to be more thermal resistant than vegetative forms of yeast, bacteria, and bacterophages. One particularly resistant undesired biocontaminant is the prion, or an infectious protein. Sterilizing prions requires special attention. To maintain aceptic operations, special considerations are needed for sealing the opening where the Stirrer Shaft enters the vessel, control valves and sampling ports. Microbes, especially shear-sensitive bacteria and mammalian cells, tend to attach to surfaces. Surface adhesion delays washout in a chemostat. The washout is more gradual if cells adhere to the vessel surfaces, and a long tail could exist if the adhesion is strong.
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Bioreactor design and operation
Bioprocess Engineering, 2013Co-Authors: Shijie LiuAbstract:For a well mixed reactor, there are three common operational modes: batch, steady CSTR and fed-batch. The selection of the operational modes depends on the catalyst stability, substrate supply, product demand and regulatory requirements. Batch operation has the best flexibility, while CSTR has the highest productivity. There are three basic reactor types for aerobic cultivation of suspended cells: internal mixing; bubble columns and loop reactors, each with different properties. Scale-up is difficult because conditions in a large vessel are more heterogeneous than in a small vessel. Scale-up problems are all related to transport processes. Scale-down techniques are useful in identifying the controlling regime at the smaller scale, where many parameters can be tested more quickly and less expensively than at the production scale. Bioreactor instrumentation and control are important for bioreactor operations. Improvements in sensor technology and the dynamical models of bioreactors are critical to improvements in control technology. Sterilization is the removal of biocontaminants or foreign organisms for a fermentation system and the surrounding equipment. Industrial fermenters and associated pipings are designed for in situ steam sterilization under pressure, or steam in place (SIP). The use of saturated steam is common and advantageous over other hot fluids. Sterilization of process fluids is dependent on the expectation of probability of successful fermentations. Stringent requirement leads to longer reduced or dimensionless sterilization time t S . Bacterial spores are known to be more thermal resistant than vegetative forms of yeast, bacteria and bacterophages. One particularly resistant undesired biocontaminant is prions, or infectious proteins. Sterilizing prions requires special attention. To maintain aceptic operations, special considerations are needed for sealing the opening where Stirrer Shaft entering the vessel, control valves and sampling ports. Microbes, especially shear sensitive bacteria and mammalian cells, tend to attach to surfaces. The attachment of suspended microbes to surfaces can be modeled as adsorption. Surface adhesion delays washout in a chemostat. The cells adhered on the vessel surfaces are less likely to be taken out of the reactor by the outflowing stream. However, the adhesion - desorption balance eventually leads to the washout if the flowrate exceeds the critical limit. The washout is more gradual if cells adhere to the vessel surfaces, and a log tail could exist if the adhesion is strong.
Dan Cascaval - One of the best experts on this subject based on the ideXlab platform.
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Study on the mixing efficiency in a basket bioreactor with immobilized yeasts cells
Environmental Engineering and Management Journal, 2011Co-Authors: Dan Cascaval, Anca-irina Galaction, Roxana Rotaru, Marius TurneaAbstract:The studies on the mixing efficiency of medium with apparent viscosity between 1 and 75 cP in a stirred bioreactor with a fixed basket bed of immobilized cells of S. cerevisiae indicated that the presence of basket leads to the significant intensification of medium circulation compared with a conventional stirred bioreactor. The mixing time recorded for the medium circulation in the outer region of basket was for about 7 to 72 times lower than that previously reached in the absence of the cylindrical bed of immobilized cells. The optimum position of the Rushton turbine on the Stirrer Shaft was found to be inside the cylindrical bed, at the superior extremity of the basket. This position offers the possibility to reach the lowest mixing time values and the most important attenuation of the negative influence of the apparent viscosity increase on the medium hydrodynamics. The mathematical correlation describing the influence of the main factors on the mixing time was established for the optimum position of turbine, and offers a good concordance with the experimental data (the average deviation was of 6.85%).
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Ethanol production in a basket bioreactor with immobilized yeasts cells 2. Study on the mixing efficiency in the outer region of basket for a double Rushton turbine impeller
Romanian Biotechnological Letters, 2011Co-Authors: Anca-irina Galaction, Marius Turnea, R. Baltaru, Dan CascavalAbstract:The studies on the mixing efficiency of medium with apparent viscosity between 1 and 75 cP in a double Rushton turbine stirred bioreactor with a fixed basket bed of immobilized cells of S. cerevisiae indicated that the presence of basket leads to the significant intensification of medium circulation compared to a conventional stirred bioreactor or to a single turbine basket bioreactor. The mixing time recorded for the medium circulation in the outer region of basket was for about 1.2 to 30 times lower than that previously reached in the absence of the cylindrical bed of immobilized cells. The optimum positions of the Rushton turbines on the Stirrer Shaft were found to be one inside the cylindrical bed, at its inferior extremity, and the other above the basket. This combination allows the possibility to reach the lowest mixing time values and the most important attenuation of the negative influence of the apparent viscosity increase on the medium hydrodynamics. The mathematical correlation describing the influence of the main factors on the mixing time was established for the optimum positions of turbines, and offers a good concordance with the experimental data (the average deviation was of ±7.42%.
Marius Turnea - One of the best experts on this subject based on the ideXlab platform.
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Study on the mixing efficiency in a basket bioreactor with immobilized yeasts cells
Environmental Engineering and Management Journal, 2011Co-Authors: Dan Cascaval, Anca-irina Galaction, Roxana Rotaru, Marius TurneaAbstract:The studies on the mixing efficiency of medium with apparent viscosity between 1 and 75 cP in a stirred bioreactor with a fixed basket bed of immobilized cells of S. cerevisiae indicated that the presence of basket leads to the significant intensification of medium circulation compared with a conventional stirred bioreactor. The mixing time recorded for the medium circulation in the outer region of basket was for about 7 to 72 times lower than that previously reached in the absence of the cylindrical bed of immobilized cells. The optimum position of the Rushton turbine on the Stirrer Shaft was found to be inside the cylindrical bed, at the superior extremity of the basket. This position offers the possibility to reach the lowest mixing time values and the most important attenuation of the negative influence of the apparent viscosity increase on the medium hydrodynamics. The mathematical correlation describing the influence of the main factors on the mixing time was established for the optimum position of turbine, and offers a good concordance with the experimental data (the average deviation was of 6.85%).
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Ethanol production in a basket bioreactor with immobilized yeasts cells 2. Study on the mixing efficiency in the outer region of basket for a double Rushton turbine impeller
Romanian Biotechnological Letters, 2011Co-Authors: Anca-irina Galaction, Marius Turnea, R. Baltaru, Dan CascavalAbstract:The studies on the mixing efficiency of medium with apparent viscosity between 1 and 75 cP in a double Rushton turbine stirred bioreactor with a fixed basket bed of immobilized cells of S. cerevisiae indicated that the presence of basket leads to the significant intensification of medium circulation compared to a conventional stirred bioreactor or to a single turbine basket bioreactor. The mixing time recorded for the medium circulation in the outer region of basket was for about 1.2 to 30 times lower than that previously reached in the absence of the cylindrical bed of immobilized cells. The optimum positions of the Rushton turbines on the Stirrer Shaft were found to be one inside the cylindrical bed, at its inferior extremity, and the other above the basket. This combination allows the possibility to reach the lowest mixing time values and the most important attenuation of the negative influence of the apparent viscosity increase on the medium hydrodynamics. The mathematical correlation describing the influence of the main factors on the mixing time was established for the optimum positions of turbines, and offers a good concordance with the experimental data (the average deviation was of ±7.42%.
Schouten J.c. - One of the best experts on this subject based on the ideXlab platform.
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Mass transfer modeling of a consecutive reaction in rotating foam reactors : selective hydrogenation of a functionalized alkyne
2012Co-Authors: Leon Matheus, Nijhuis T.a., Schaaf Van Der, J., Schouten J.c.Abstract:The external and internal mass transfer for a rotating foam Stirrer reactor has been studied using the hydrogenation of 3-methyl-1-pentyn-3-ol as a model reaction. Catalytic foam Stirrers with different number of pores per linear inch (ppi) and washcoating thicknesses are used and their performance are described in terms of activity and selectivity. The liquid-solid mass transfer does not limit the overall reaction rate when a 20 ppi foam is used. For this catalytic foam Stirrer, a kLSaLS value of 0.2 s-1 is estimated at 300 rpm. The use of finer pore foam structures is not convenient due to a drastic decrease of catalyst surface refreshment. As a result, the lower kLS value negates the benefit of a larger area (aLS) resulting in a lower liquid-solid mass transfer. The catalyst accessibility is a controlling factor in this fast reaction. The optimal washcoat thickness to avoid diffusion limitations is 5 µm. Gas-liquid mass transfer rate is not a limiting factor. A kGLaGL of 0.6 s-1 is measured at 300 rpm by the physical adsorption method. When compared to the conventional slurry reactor, the liquid-solid and the gas-liquid mass transfer rates are 17 and 6 times higher, respectively. However, the intrinsic activity of the foam catalyst is 4.6 times less than the slurry catalyst prepared with the same palladium loading. This is explained by a difference in palladium dispersion caused by a non homogenous concentration of active sites along the washcoat layer. On the other hand, the less active foam catalyst leads to higher selectivity. The production rate is then increased by mounting more active blades on the Stirrer Shaft, thus creating more surface area for catalyst deposition while still keeping the high accessibility of a 4 µm washcoat layer. Hence, rotating foam reactors have promising applications for multiphase processes. High mass transfer rates can be easily achieved, catalyst filtering is not longer needed and reusability of the foam catalyst is possible. -------------------------------------------------------------------------------
Jc Jaap Schouten - One of the best experts on this subject based on the ideXlab platform.
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Mass transfer modeling of a consecutive reaction in rotating foam Stirrer reactors: Selective hydrogenation of a functionalized alkyne
Chemical Engineering Science, 2012Co-Authors: María A. De León, T.a. Nijhuis, J. Van Der Schaaf, Jc Jaap SchoutenAbstract:Abstract The external and internal mass transfer for a rotating foam Stirrer reactor has been studied using the hydrogenation of 3-methyl-1-pentyn-3-ol as a model reaction. Catalytic foam Stirrers with different number of pores per linear inch (ppi) and washcoating thicknesses are used and their performance are described in terms of activity and selectivity. The liquid–solid mass transfer does not limit the overall reaction rate when a 20 ppi foam is used. For this catalytic foam Stirrer, a kLSaLS value of 0.2 s−1 is estimated at 300 rpm. The use of finer pore foam structures is not convenient due to a drastic decrease of catalyst surface refreshment. As a result, the lower kLS value negates the benefit of a larger area (aLS) resulting in a lower liquid–solid mass transfer. The catalyst accessibility is a controlling factor in this fast reaction. The optimal washcoat thickness to avoid diffusion limitations is 5 μm. Gas–liquid mass transfer rate is not a limiting factor. A kGLaGL of 0.6 s−1 is measured at 300 rpm by the physical absorption method. When compared to the conventional slurry reactor, the liquid–solid and the gas–liquid mass transfer rates are 17 and 6 times higher, respectively. However, the intrinsic activity of the foam catalyst is 4.6 times less than the slurry catalyst prepared with the same palladium loading. This is explained by a difference in palladium dispersion caused by a non-homogenous concentration of active sites along the washcoat layer. On the other hand, the less active foam catalyst leads to higher selectivity. The production rate is then increased by mounting more active blades on the Stirrer Shaft, thus creating more surface area for catalyst deposition while still keeping the high accessibility of a 4 μm washcoat layer. Hence, rotating foam reactors have promising applications for multiphase processes. High mass transfer rates can be easily achieved, catalyst filtering is not longer needed and reusability of the foam catalyst is possible.