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Oxygen Transfer Coefficient (oxygen + transfer_coefficient)
Selected AbstractsDesign and operation of unbaffled aerated agitated vessels with unsteadily forward,reverse rotating impellers handling viscous Newtonian liquidsJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 4 2003Masanori Yoshida Abstract Design and operation of unbaffled aerated agitated vessels with multiple unsteadily forward,reverse rotating impellers (AJITERs) for viscous Newtonian liquids were studied. The effects of operating conditions such as gas sparging rate, agitation rate and the number of impeller stages, geometrical conditions such as the diameters of vessel and impeller, and the physical properties of liquids on the drag and added moment of inertia coefficients, necessary to predict the average and maximum power consumptions of the impellers in AJITERs, were evaluated and the empirical relationships which estimate values of each of these coefficients are presented. The effects of operating conditions, geometrical conditions and liquid physical properties on the gas hold-up, ,gD, and volumetric oxygen transfer coefficient, kLaD, were evaluated in relation to the total power input which is the sum of the average power consumption of impellers, ie average agitation power input, and aeration power input. Empirical relationships, useful for design and operation of AJITERs, were obtained for each viscosity range, where the dependences of ,gD and kLaD on the specific total power input and superficial gas velocity differed, to predict ,gD and kLaD respectively as a function of the specific total power input, superficial gas velocity and liquid physical properties. © 2003 Society of Chemical Industry [source] Flow and mass transfer in aerated viscous Newtonian liquids in an unbaffled agitated vessel having alternating forward,reverse rotating impellersJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 11 2001Masanori Yoshida Abstract Flow and mass transfer characteristics in aerated viscous Newtonian liquids were studied for an unbaffled aerated agitated vessel with alternating rotating impellers (AAVAI), ie with multiple forward,reverse rotating impellers having four delta blades. The effects of operating conditions such as gas sparging rate, agitation rate and the number of impeller stages, and the liquid physical properties (viscosity) on the gas hold-up, ,gD, and volumetric oxygen transfer coefficient, kLaD were evaluated experimentally. The dependences of ,gD and kLaD on the specific total power input and superficial gas velocity differed, depending on the ranges of liquid viscosity. Empirical relationships are presented for each viscosity range to predict ,gD and kLaD as a function of the specific total power input, superficial gas velocity and viscosity of liquid. Based on a comparative investigation of the volumetric coefficient in terms of the specific total power input between the AAVAI and conventional aerated agitated vessels (CAAVs) having unidirectionally rotating impellers, the usefulness of AAVAI as a gas,liquid agitator treating viscous Newtonian liquids is also discussed. © 2001 Society of Chemical Industry [source] Dynamic measurement of the volumetric oxygen transfer coefficient in fermentation systems,BIOTECHNOLOGY & BIOENGINEERING, Issue 5 2009B. Bandyopadhyay First page of article [source] Effect of Suspended Liposomes on Hydrodynamic and Oxygen Transfer Properties in a Mini-Scale External Loop Airlift Bubble ColumnCHEMICAL ENGINEERING & TECHNOLOGY (CET), Issue 9 2006M. Yoshimoto Abstract The circulating liquid velocity, gas holdup, bubble size distribution, and liquid phase oxygen transfer coefficient were measured in a mini-scale external loop airlift bubble column (MELBC) with the liquid volume suspending enzyme-free liposomes of varying diameters. These values were compared to those for liposome-free MELBC, normal bubble column (NBC), and a larger scale airlift column. The liposomes suspended in the MELBC are incorporated into the liquid film around the bubbles, leading to the development of a foam layer, where the incorporated liposomes exert negligible effect on the oxygen transfer in the film. [source] Oxygen transfer effects in ,-lactamase fermentation by Bacillus licheniformis in a glucose-based defined mediumJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 9 2005nar Çal Abstract The effects of oxygen transfer on the ,-lactamase production by Bacillus licheniformis were investigated in a glucose-based defined medium. The experiments were conducted in 3.0 dm3 batch bioreactor systems at three different air inlet (QO/VR = 0.2, 0.5 and 1.0 vvm) and agitation rates (N = 250, 500 and 750 min,1). During the fermentation, the concentrations of the cell, glucose, by-products, ie organic and amino acids, oxygen transfer coefficients (KLa), yield coefficients, specific rates and oxygen uptake rates (OUR) were determined, in addition to ,-lactamase activities. The highest ,-lactamase activity was obtained at QO/VR = 0.5 vvm and N = 500 min,1 and at QO/VR = 0.2 vvm and N = 500 min,1 conditions, as caA = 90 U cm,3. The highest cell concentration was obtained as CX = 0.67 kg m,3 at QO/VR = 0.5 vvm and N = 750 min,1 and at QO/VR = 0.2 vvm and N = 750 min,1 conditions. The values of KLa increased with increasing agitation and aeration rates and varied between 0.007 and 0.044 s,1, and the OUR varied between 0.4 and 1.6 mol m,3 s,1. With increasing QO/VR and/or N, the Damköhler number (ie the oxygen transfer limitation) decreased owing to the increase in mass transfer coefficients (KLa). The highest instantaneous yield of cell on substrate (YX/S) and yield of cell on oxygen (YX/O) values were respectively obtained at 0.5 vvm and 500 min,1 conditions at t = 2 h as YX/S = 0.72 kg kg,1 and YX/O = 1.49 kg kg,1. The highest instantaneous yield of substrate on oxygen (YS/O) was obtained at 0.5 vvm and 750 min,1 conditions at t = 20 h as YS/O = 8.07 kg kg,1. Copyright © 2005 Society of Chemical Industry [source] New milliliter-scale stirred tank bioreactors for the cultivation of mycelium forming microorganismsBIOTECHNOLOGY & BIOENGINEERING, Issue 3 2010Ralf Hortsch Abstract A novel milliliter-scale stirred tank bioreactor was developed for the cultivation of mycelium forming microorganisms on a 10 milliliter-scale. A newly designed one-sided paddle impeller is driven magnetically and rotates freely on an axis in an unbaffled reaction vessel made of polystyrene. A rotating lamella is formed which spreads out along the reactor wall. Thus an enhanced surface-to-volume ratio of the liquid phase is generated where oxygen is introduced via surface aeration. Volumetric oxygen transfer coefficients (kLa),>,0.15,s,1 were measured. The fast moving liquid lamella efficiently prevents wall growth and foaming. Mean power consumption and maximum local energy dissipation were measured as function of operating conditions in the milliliter-scale stirred tank bioreactor (V,=,10,mL) and compared to a standard laboratory-scale stirred tank bioreactor with six-bladed Rushton turbines (V,=,2,000,mL). Mean power consumption increases with increasing impeller speed and shows the same characteristics and values on both scales. The maximum local energy dissipation of the milliliter-scale stirred tank bioreactor was reduced compared to the laboratory-scale at the same mean volumetric power input. Hence the milliliter impeller distributes power more uniformly in the reaction medium. Based on these data a reliable and robust scale-up of fermentation processes is possible. This was demonstrated with the cultivation of the actinomycete Streptomyces tendae on both scales. It was shown that the process performances were equivalent with regard to biomass concentration, mannitol consumption and production of the pharmaceutical relevant fungicide nikkomycin Z up to a process time of 120,h. A high parallel reproducibility was observed on the milliliter-scale (standard deviation,<,8%) with up to 48 stirred tank bioreactors operated in a magnetic inductive drive. Rheological behavior of the culture broth was measured and showed a highly viscous shear-thinning non-Newtonian behavior. The newly developed one-sided paddle impellers operated in unbaffled reactors on a 10 milliliter-scale with a magnetic inductive drive for up to 48 parallel bioreactors allows for the first time the parallel bioprocess development with mycelium forming microorganisms. This is especially important since these kinds of cultivations normally exhibit process times of 100,h and more. Thus the operation of parallel stirred tank reactors will have the potential to reduce process development times drastically. Biotechnol. Bioeng. 2010; 106: 443,451. © 2010 Wiley Periodicals, Inc. [source] Production of L(+)-lactic acid from glucose and starch by immobilized cells of Rhizopus oryzae in a rotating fibrous bed bioreactorBIOTECHNOLOGY & BIOENGINEERING, Issue 1 2002Abdullatif Tay Abstract A rotating fibrous-bed bioreactor (RFB) was developed for fermentation to produce L(+)-lactic acid from glucose and cornstarch by Rhizopus oryzae. Fungal mycelia were immobilized on cotton cloth in the RFB for a prolonged period to study the fermentation kinetics and process stability. The pH and dissolved oxygen concentration (DO) were found to have significant effects on lactic acid productivity and yield, with pH 6 and 90% DO being the optimal conditions. A high lactic acid yield of 90% (w/w) and productivity of 2.5 g/L·h (467 g/h·m2) was obtained from glucose in fed-batch fermentation. When cornstarch was used as the substrate, the lactic acid yield was close to 100% (w/w) and the productivity was 1.65 g/L·h (300 g/h·m2). The highest concentration of lactic acid achieved in these fed-batch fermentations was 127 g/L. The immobilized-cells fermentation in the RFB gave a virtually cell-free fermentation broth and provided many advantages over conventional fermentation processes, especially those with freely suspended fungal cells. Without immobilization with the cotton cloth, mycelia grew everywhere in the fermentor and caused serious problems in reactor control and operation and consequently the fermentation was poor in lactic acid production. Oxygen transfer in the RFB was also studied and the volumetric oxygen transfer coefficients under various aeration and agitation conditions were determined and then used to estimate the oxygen transfer rate and uptake rate during the fermentation. The results showed that the oxygen uptake rate increased with increasing DO, indicating that oxygen transfer was limited by the diffusion inside the mycelial layer. © 2002 Wiley Periodicals, Inc. Biotechnol Bioeng 80: 1,12, 2002. [source] | ||||||||||