Optical sensor enabled rocking T-flasks as novel upstream bioprocessing tools

During the past decade, novel disposable cell culture vessels (generally referred to as Process Scouting Devices or PSDs) have become increasingly popular for laboratory scale studies and seed culture generation. However, the lack of engineering characterization and online monitoring tools for PSDs makes it difficult to elucidate their oxygen transfer capabilities. In this study, a mass transfer characterization (k_La) of sensor enabled static and rocking T‐flasks is presented and compared with other non‐instrumented PSDs such as CultiFlask 50®, spinner flasks, and SuperSpinner D 1000®. We have also developed a mass transfer empirical correlation that accounts for the contribution of convection and diffusion to the volumetric mass transfer coefficient (k_La) in rocking T‐flasks. We also carried out a scale‐down study at matched k_La between a rocking T75‐flask and a 10 L (2 L filling volume) wave bioreactor (Cultibag®) and we observed similar DO and pH profiles as well as maximum cell density and protein titer. However, in this scale‐down study, we also observed a negative correlation between cell growth and protein productivity between the rocking T‐flask and the wave bioreactor. We hypothesize that this negative correlation can be due to hydrodynamic stress difference between the rocking T‐flask and the Cultibag. As both cell culture devices share key similarities such as type of agitation (i.e., rocking), oxygen transfer capabilities (i.e., k_La) and disposability, we argue that rocking T‐flasks can be readily integrated with wave bioreactors, making the transition from research‐scale to manufacturing‐scale a seamless process. Biotechnol. Bioeng. 2012;109: 2295–2305. © 2012 Wiley Periodicals, Inc.     

Studies on fluid dynamics of the flow field and gas transfer in orbitally shaken tubes

Orbitally shaken cylindrical bioreactors [OrbShake bioreactors (OSRs)] without an impeller or sparger are increasingly being used for the suspension cultivation of mammalian cells. Among small volume OSRs, 50‐mL tubes with a ventilated cap (OSR50), originally derived from standard laboratory centrifuge tubes with a conical bottom, have found many applications including high‐throughput screening for the optimization of cell cultivation conditions. To better understand the fluid dynamics and gas transfer rates at the liquid surface in OSR50, we established a three‐dimensional simulation model of the unsteady liquid forms (waves) in this vessel. The studies verified that the operating conditions have a large effect on the interfacial surface. The volumetric mass transfer coefficient (k_La) was determined experimentally and from simulations under various working conditions. We also determined the liquid‐phase mass transfer coefficient (k_L) and the specific interfacial area (a) under different conditions to demonstrate that the value of a affected the gas transfer rate more than did the value of k_L. High oxygen transfer rates, sufficient for supporting the high‐density culture of mammalian cells, were found. Finally, the average axial velocity of the liquid was identified to be an important parameter for maintaining cells in suspension. Overall these studies provide valuable insights into the preferable operating conditions for the OSR50, such as those needed for cell cultures requiring high oxygen levels. © 2016 American Institute of Chemical Engineers Biotechnol. Prog., 33:192–200, 2017     

Development of a scale-up strategy for Chinese hamster ovary cell culture processes using the kLa ratio as a direct indicator of gas stripping conditions

Herein, we described a scale-up strategy focused on the dissolved carbon dioxide concentration (dCO₂) during fed-batch cultivation of Chinese hamster ovary cells. A fed-batch culture process for a 2000-L scale stainless steel (SS) bioreactor was scaled-up from similarly shaped 200-L scale bioreactors based on power input per unit volume (P/V). However, during the 2000-L fed-batch culture, the dCO₂ was higher compared with the 200-L scale bioreactor. Therefore, we developed an alternative approach by evaluating the k_La values of O₂ (k_La[O₂]) and CO₂ [k_La(CO₂)] in the SS bioreactors as a scale-up factor for dCO₂ reduction. The k_La ratios [k_La(CO₂)/k_La(O₂)] were different between the 200-L and 2000-L bioreactors under the same P/V condition. When the agitation conditions were changed, the k_La ratio of the 2000-L scale bioreactor became similar and the P/V value become smaller compared with those of the 200-L SS bioreactor. The dCO₂ trends in fed-batch cultures performed in 2000-L scale bioreactors under the modified agitation conditions were similar to the control. This k_La ratio method was used for process development in single-use bioreactors (SUBs) with shapes different from those of the SS bioreactor. The k_La ratios for the SUBs were evaluated and conditions that provided k_La ratios similar to the 200-L scale SS bioreactors were determined. The cell culture performance and product quality at the end of the cultivation process were comparable for all tested SUBs. Therefore, we concluded that the k_La ratio is a powerful scale-up factor useful to control dCO₂ during fed-batch cultures.     

Characterizing the fluid dynamics in the flow fields of cylindrical orbitally shaken bioreactors with different geometry sizes

Orbitally shaken bioreactors (OSRs) are commonly used for the cultivation of mammalian cells in suspension. To aid the geometry designing and optimizing of OSRs, we conducted a three‐dimensional computational fluid dynamics (CFD) simulation to characterize the flow fields in a 10 L cylindrical OSR with different vessel diameters. The liquid wave shape captured by a camera experimentally validated the CFD models established for the cylindrical OSR. The geometry size effect on volumetric mass transfer coefficient (k_La) and hydromechanical stress was analyzed by varying the ratio of vessel diameter (d) to liquid height at static (h_L), d/h_L. The highest value of k_La about 30 h^?1 was observed in the cylindrical vessel with the d/h_L of 6.35. Moreover, the magnitudes of shear stress and energy dissipation rate in all the vessels tested were below their minimum values causing cells damage separately, which indicated that the hydromechanical‐stress environment in OSRs is suitable for cells cultivation in suspension. Finally, the CFD results suggested that the d/h_L higher than 8.80 should not be adopted for the 10 L cylindrical OSR at the shaking speed of 180 rpm because the “out of phase” state probably will happen there.     

Application of high‐throughput mini‐bioreactor system for systematic scale‐down modeling,process characterization,and control strategy development

High‐throughput systems and processes have typically been targeted for process development and optimization in the bioprocessing industry. For process characterization, bench scale bioreactors have been the system of choice. Due to the need for performing different process conditions for multiple process parameters, the process characterization studies typically span several months and are considered time and resource intensive. In this study, we have shown the application of a high‐throughput mini‐bioreactor system viz. the Advanced Microscale Bioreactor (ambr15^TM), to perform process characterization in less than a month and develop an input control strategy. As a pre‐requisite to process characterization, a scale‐down model was first developed in the ambr system (15 mL) using statistical multivariate analysis techniques that showed comparability with both manufacturing scale (15,000 L) and bench scale (5 L). Volumetric sparge rates were matched between ambr and manufacturing scale, and the ambr process matched the pCO₂ profiles as well as several other process and product quality parameters. The scale‐down model was used to perform the process characterization DoE study and product quality results were generated. Upon comparison with DoE data from the bench scale bioreactors, similar effects of process parameters on process yield and product quality were identified between the two systems. We used the ambr data for setting action limits for the critical controlled parameters (CCPs), which were comparable to those from bench scale bioreactor data. In other words, the current work shows that the ambr15^TM system is capable of replacing the bench scale bioreactor system for routine process development and process characterization. © 2015 American Institute of Chemical Engineers Biotechnol. Prog., 31:1623–1632, 2015     

Effects of oxygen volumetric mass transfer coefficient and pH on lipase production by Staphylococcus warneri EX17

The principal objectives of this study were to evaluate the kinetics of lipase production by Staphylococcus warneri EX17 under different oxygen volumetric mass transfer coefficients (k_La) and pH conditions in submerged bioreactors, using glycerol (a biodiesel by-product) as a carbon source. Cultivations were conducted at different k_La (26, 38, 50, and 83 h⁻¹) and pH values (6.0, 7.0, and 8.0). The optimal k_La and pH were 38 h⁻¹ and 7.0, respectively. Under these conditions, the maximal cell production obtained was 8.0 g/L, and the volumetric and specific lipase production reached high levels of activity, approximately 800 U/L and 150 U/g cell, respectively, after 12 h of cultivation. This result was approximately five times higher than that obtained in the shake flask cultures. The relationship between cell growth and lipase production was found to be associated with growth by the Luedeking-Piret model.     

Characterizing the fluid dynamics of the inverted frustoconical shaking bioreactor

The authors conducted a three‐dimensional computational fluid dynamics (CFD) simulation to calculate the flow field in the inverted frustoconical shaking bioreactor with 5 L working volume (IFSB‐5L). The CFD models were established for the IFSB‐5L at different operating conditions (different shaking speeds and filling volumes) and validated by comparison of the liquid height distribution in the agitated IFSB‐5L. The “out of phase” operating conditions were characterized by analyzing the flow field in the IFSB‐5L at different filling volumes and shaking speeds. The values of volumetric power consumption (P/V_L) and volumetric mass transfer coefficient (k_La) were determined from simulated and experimental results, respectively. Finally, the operating condition effect on P/V_L and k_La was investigated. © 2018 American Institute of Chemical Engineers Biotechnol. Prog., 34:478–485, 2018     

The baffled microtiter plate: Increased oxygen transfer and improved online monitoring in small scale fermentations

Most experiments in screening and process development are performed in shaken bioreactors. Today, microtiter plates are the preferred vessels for small‐scale microbial cultivations in high throughput, even though they have never been optimized for this purpose. To interpret the experimental results correctly and to obtain a base for a meaningful scale‐up, sufficient oxygen supply to the culture liquid is crucial. For shaken bioreactors this problem can generally be addressed by the introduction of baffles. Therefore, the focus of this study is to investigate how baffling and the well geometry affect the maximum oxygen transfer capacity (OTR_max) in microtiter plates. On a 48‐well plate scale, 30 different cross‐section geometries of a well were studied. It could be shown that the introduction of baffles into the common circular cylinder of a microtiter plate well doubles the maximum oxygen transfer capacity, resulting in values above 100 mmol/L/h (k_La > 600 1/h). To also guarantee a high volume for microbial cultivation, it is important to maximize the filling volume, applicable during orbital shaking. Additionally, the liquid height at the well bottom was examined, which is a decisive parameter for online‐monitoring systems such as the BioLector. This technology performs fiber‐optical measurements through the well bottom, therefore requires a constant liquid height at all shaking frequencies. Ultimately, a six‐petal flower‐shaped well geometry was shown to be the optimal solution taking into account all aforementioned criteria. With its favorable culture conditions and the possibility for unrestricted online monitoring, this novel microtiter plate is an efficient tool to gain meaningful results for interpreting and scaling‐up experiments in clone screening and bioprocess development. Biotechnol. Bioeng. 2009;103: 1118–1128. © 2009 Wiley Periodicals, Inc.     

Application of multivariate analysis and mass transfer principles for refinement of a 3‐L bioreactor scale‐down model—when shake flasks mimic 15,000‐L bioreactors better

Characterization of manufacturing processes is key to understanding the effects of process parameters on process performance and product quality. These studies are generally conducted using small‐scale model systems. Because of the importance of the results derived from these studies, the small‐scale model should be predictive of large scale. Typically, small‐scale bioreactors, which are considered superior to shake flasks in simulating large‐scale bioreactors, are used as the scale‐down models for characterizing mammalian cell culture processes. In this article, we describe a case study where a cell culture unit operation in bioreactors using one‐sided pH control and their satellites (small‐scale runs conducted using the same post‐inoculation cultures and nutrient feeds) in 3‐L bioreactors and shake flasks indicated that shake flasks mimicked the large‐scale performance better than 3‐L bioreactors. We detail here how multivariate analysis was used to make the pertinent assessment and to generate the hypothesis for refining the existing 3‐L scale‐down model. Relevant statistical techniques such as principal component analysis, partial least square, orthogonal partial least square, and discriminant analysis were used to identify the outliers and to determine the discriminatory variables responsible for performance differences at different scales. The resulting analysis, in combination with mass transfer principles, led to the hypothesis that observed similarities between 15,000‐L and shake flask runs, and differences between 15,000‐L and 3‐L runs, were due to pCO₂ and pH values. This hypothesis was confirmed by changing the aeration strategy at 3‐L scale. By reducing the initial sparge rate in 3‐L bioreactor, process performance and product quality data moved closer to that of large scale. © 2015 American Institute of Chemical Engineers Biotechnol. Prog., 31:1370–1380, 2015     

A case study in converting disposable process scouting devices into disposable bioreactors as a future bioprocessing tool

In this study, we perform mass transfer characterization (k_La) on a novel mechanically driven/stirred Process Scouting Device, PSD, (SuperSpinner D 1000®, SSD) and demonstrate that this novel device can be viewed as disposable bioreactor. Using patch‐based optical sensors, we were able to monitor critical cell culture environmental conditions such as dissolved oxygen (DO) and pH in SSD for comparison to a 1 L standard spinner (SS) flask. We also coupled these mass transfer studies with mixing time studies where we observed relative high mixing times (5.2 min) that are typically observed in production scale bioreactors. Decreasing the mixing time 3.5‐fold resulted in 30% increase in k_La (from 2.3 to 3.0 h^?1) and minimum DO level increased from 0% to 20% for our model hybridoma cell line. Finally, maximum viable cell density and protein titer stayed within ±20% of historical data, from our standard 5 L stirred bioreactor (Biostat®) operated under active DO control. Biotechnol. Bioeng. 2012; 109: 2790–2797. © 2012 Wiley Periodicals, Inc.     

A new dynamic model for highly efficient mass transfer in aerated bioreactors and consequences for kLa identification

Gas–liquid mass transfer is often rate‐limiting in laboratory and industrial cultures of aerobic or autotrophic organisms. The volumetric mass transfer coefficient k_La is a crucial characteristic for comparing, optimizing, and upscaling mass transfer efficiency of bioreactors. Reliable dynamic models and resulting methods for parameter identification are needed for quantitative modeling of microbial growth dynamics. We describe a laboratory‐scale stirred tank reactor (STR) with a highly efficient aeration system (k_La ≈ 570 h^?1). The reactor can sustain yeast culture with high cell density and high oxygen uptake rate, leading to a significant drop in gas concentration from inflow to outflow (by 21%). Standard models fail to predict the observed mass transfer dynamics and to identify k_La correctly. In order to capture the concentration gradient in the gas phase, we refine a standard ordinary differential equation (ODE) model and obtain a system of partial integro‐differential equations (PIDE), for which we derive an approximate analytical solution. Specific reactor configurations, in particular a relatively short bubble residence time, allow a quasi steady‐state approximation of the PIDE system by a simpler ODE model which still accounts for the concentration gradient. Moreover, we perform an appropriate scaling of all variables and parameters. In particular, we introduce the dimensionless overall efficiency κ, which is more informative than k_La since it combines the effects of gas inflow, exchange, and solution. Current standard models of mass transfer in laboratory‐scale aerated STRs neglect the gradient in the gas concentration, which arises from highly efficient bubbling systems and high cellular exchange rates. The resulting error in the identification of κ (and hence k_La) increases dramatically with increasing mass transfer efficiency. Notably, the error differs between cell‐free and culture‐based methods of parameter identification, potentially confounding the determination of the “biological enhancement” of mass transfer. Our new model provides an improved theoretical framework that can be readily applied to aerated bioreactors in research and biotechnology. Biotechnol. Bioeng. 2012; 109: 2997–3006. © 2012 Wiley Periodicals, Inc.     

Xylitol Production from D‐Xylose at Different Oxygen Transfer Coefficients in a Batch Bioreactor

Conversion of D‐xylose to xylitol by Candida boidinii NRRL Y‐17213 was studied under anaerobic and oxygen limited conditions by varying the oxygen transfer coefficient k_La. Shake flask experiments were used to provide the preliminary information required to perform experiments in a bioreactor. The yeast did not grow under fully anaerobic conditions, but anaerobic formations of xylitol, ethanol, ribitol, and glycerol were observed as well as D‐xylose assimilation of 11 %. In shake flasks, with an initial D‐xylose concentration of 50 g/L, an increase in k_La from 8 to 46 h^–1 resulted in a faster growth, higher rate of substrate uptake and lower yields of products. The highest xylitol productivity (0.052 g/L h) was attained at k_La = 8 h^–1. At k_La = 46 h^–1, 98.6 % of D‐xylose was consumed and mainly converted to biomass. Using 130 g/L D‐xylose, k_La was varied in the fermenter from 26 to 78 h^–1. The percentage of consumed D‐xylose increased from 31 % at k_La = 26 h^–1 to 93–94 % at all other aeration levels. Biomass yield increased with k_La, whereas ethanol, ribitol, and glycerol yields exhibited an opposite dependence on the oxygenation level. The most favorable oxygen transfer coefficient for xylitol formation, in the fermenter, was k_La = 47 h^–1 when its concentration (57.5 g/L) surpassed ethanol accumulation by 3.6‐fold, and the glycerol plus ribitol by 10‐fold. Concurrently, xylitol yield and productivity reached 0.45 g/g and 0.26 g/L h, respectively. The volumetric xylitol productivity was affected more by changes in the aeration than the corresponding yield.     

Oxygen mass transfer and scale-up studies in baffled roller bioreactors

Oxygen mass transfer was studied in conventional, bead mill and baffled roller bioreactors. Using central composite rotational design, impacts of size, rotation speed and working volume on the oxygen mass transfer were evaluated. Baffled roller bioreactor outperformed its conventional and bead mill counterparts, with the highest k _L a obtained in these configurations being 0.58, 0.19, 0.41 min^?1, respectively. Performances of the bead mill and baffled roller bioreactor were only comparable when a high bead loading (40 %) was applied. Regardless of configuration increase in rotation speed and decrease in working volume improved the oxygen mass transfer rate. Increase in size led to enhanced mass transfer and higher k _L a in baffled roller bioreactor (0.49 min^?1 for 2.2 L and 1.31 min^?1 for 55 L bioreactors). Finally, the experimentally determined k _L a in the baffled roller bioreactors of different sizes fit reasonably well to an empirical correlation describing the k _L a in terms of dimensionless numbers.     

A shaken disposable bioreactor system for controlled insect cell cultivations at milliliter‐scale

While wave‐mixed and stirred bag bioreactors are common devices for rapid, safe insect cell culture‐based production at liter‐scale, orbitally shaken disposable flasks are mainly used for screening studies at milliliter‐scale. In contrast to the two aforementioned bag bioreactor types, which can be operated with standard or disposable sensors, shaker flasks have not been instrumented until recently. The combination of 250 mL disposable shake flasks with PreSens's Shake Flask Reader enables both pH and dissolved oxygen to be measured, as well as allowing characterization of oxygen mass transfer. Volumetric oxygen transfer coefficients (k_La‐values) for PreSens 250 mL disposable shake flasks, which were determined for the first time in insect cell culture medium at varying culture volumes and shaker frequencies, ranged between 4.4 and 37.9/h. Moreover, it was demonstrated that online monitoring of dissolved oxygen in shake flasks is relevant for limitation‐free growth of insect cells up to high cell densities in batch mode (1.6×10⁷ cells/mL) and for the efficient expression of an intracellular model protein.     

Correlation between mass transfer coefficient k<Subscript>L</Subscript>a and relevant operating parameters in cylindrical disposable shaken bioreactors on a bench-to-pilot scale

Background

Among disposable bioreactor systems, cylindrical orbitally shaken bioreactors show important advantages. They provide a well-defined hydrodynamic flow combined with excellent mixing and oxygen transfer for mammalian and plant cell cultivations. Since there is no known universal correlation between the volumetric mass transfer coefficient for oxygen k_La and relevant operating parameters in such bioreactor systems, the aim of this current study is to experimentally determine a universal k_La correlation.

Results

A Respiration Activity Monitoring System (RAMOS) was used to measure k_La values in cylindrical disposable shaken bioreactors and Buckingham’s π-Theorem was applied to define a dimensionless equation for k_La. In this way, a scale- and volume-independent k_La correlation was developed and validated in bioreactors with volumes from 2 L to 200 L. The final correlation was used to calculate cultivation parameters at different scales to allow a sufficient oxygen supply of tobacco BY-2 cell suspension cultures.

Conclusion

The resulting equation can be universally applied to calculate the mass transfer coefficient for any of seven relevant cultivation parameters such as the reactor diameter, the shaking frequency, the filling volume, the viscosity, the oxygen diffusion coefficient, the gravitational acceleration or the shaking diameter within an accuracy range of +/? 30%. To our knowledge, this is the first k_La correlation that has been defined and validated for the cited bioreactor system on a bench-to-pilot scale.

     

Determination of specific oxygen uptake rate of Photorhabdus luminescens during submerged culture in lab scale bioreactor

Photorhabdus luminescens, a bacterial symbiont of entomoparasitic nematodes, was cultured in a 10 L bioreactor. Cellular density and bioluminescence were recorded and volumetric oxygen transfer coefficient (k_La) and specific oxygen transfer rates were determined during the batch process. Exponential phase of the bacterium lasted for 20 h, showing a maximum specific growth rate of 0.339 h^?1 in a defined medium. Bioluminescence peaked within 21h, and was maintained until the end of the batch process (48 h). The specific oxygen uptake rate (SOUR) was high during both lag and early exponential phase, and eventually reached a stable value of 0.33 mmol g^?1 h^?1 during stationary phase. Maintenance of 200 rpm agitation and 1.4 volume of air per volume of medium per minute (vvm) aeration, gave rise to a k_La value of 39.5 h^?1. This k_La value was sufficient to meet the oxygen demand of 14.4 g L^?1 (DCW) biomass. This research is particularly relevant since there are no reports available on SOURs of symbiotic bacteria or their nematode partners. The insight gained through this study will be useful during the development of a submerged monoxenic culture of Heterorhabditis bacteriophora and its symbiotic bacterium P. luminescens in bioreactors.     

Using CFD simulations and statistical analysis to correlate oxygen mass transfer coefficient to both geometrical parameters and operating conditions in a stirred-tank bioreactor

Optimization of a bioreactor design can be an especially challenging process. For instance, testing different bioreactor vessel geometries and different impeller and sparger types, locations, and dimensions can lead to an exceedingly large number of configurations and necessary experiments. Computational fluid dynamics (CFD), therefore, has been widely used to model multiphase flow in stirred-tank bioreactors to minimize the number of optimization experiments. In this study, a multiphase CFD model with population balance equations are used to model gas–liquid mixing, as well as gas bubble distribution, in a 50 L single-use bioreactor vessel. The vessel is the larger chamber in an early prototype of a multichamber bioreactor for mammalian cell culture. The model results are validated with oxygen mass transfer coefficient (k_La) measurements within the prototype. The validated model is projected to predict the effect of using ring or pipe spargers of different sizes and the effect of varying the impeller diameter on k_La. The simulations show that ring spargers result in a superior k_La compared to pipe spargers, with an optimum sparger-to-impeller diameter ratio of 0.8. In addition, larger impellers are shown to improve k_La. A correlation of k_La is presented as a function of both the reactor geometry (i.e., sparger-to-impeller diameter ratio and impeller-to-vessel diameter ratio) and operating conditions (i.e., Reynolds number and gas flow rate). The resulting correlation can be used to predict k_La in a bioreactor and to optimize its design, geometry, and operating conditions.     

Large‐scale culture of a megakaryocytic progenitor cell line with a single‐use bioreactor system

The increasing application of regenerative medicine has generated a growing demand for stem cells and their derivatives. Single‐use bioreactors offer an attractive platform for stem cell expansion owing to their scalability for large‐scale production and feasibility of meeting clinical‐grade standards. The current work evaluated the capacity of a single‐use bioreactor system (1 L working volume) for expanding Meg01 cells, a megakaryocytic (MK) progenitor cell line. Oxygen supply was provided by surface aeration to minimize foaming and orbital shaking was used to promote oxygen transfer. Oxygen transfer rates (k_La) of shaking speeds 50, 100, and 125 rpm were estimated to be 0.39, 1.12, and 10.45 h^?1, respectively. Shaking speed was a critical factor for optimizing cell growth. At 50 rpm, Meg01 cells exhibited restricted growth due to insufficient mixing. A negative effect occurred when the shaking speed was increased to 125 rpm, likely caused by high hydrodynamic shear stress. The bioreactor culture achieved the highest growth profile when shaken at 100 rpm, achieving a total expansion rate up to 5.7‐fold with a total cell number of 1.2 ± 0.2 × 10⁹ cells L^?1. In addition, cells expanded using the bioreactor system could maintain their potency to differentiate following the MK lineage, as analyzed from specific surface protein and morphological similarity with the cells grown in the conventional culturing system. Our study reports the impact of operational variables such as shaking speed for growth profile and MK differentiation potential of a progenitor cell line in a single‐use bioreactor. © 2017 American Institute of Chemical Engineers Biotechnol. Prog., 34:362–369, 2018     

A test facility for fritted spargers of production-scale-bioreactors

The production of therapeutic proteins requires qualification of equipment components and appropriate validation procedures for all operations. Since protein productions are typically performed in bioreactors using aerobic cultivation processes air sparging is an essential factor. As recorded in literature, besides ring spargers and open pipe, sinter frits are often used as sparging elements in large scale bioreactors. Due to the manufacturing process these frits have a high lot-to-lot product variability. Experience shows this is a practical problem for use in production processes of therapeutic proteins, hence frits must be tested before they can be employed. The circumstance of checking quality and performance of frits as sparging elements was investigated and various possibilities have been compared. Criteria have been developed in order to evaluate the sparging performance under conditions comparable to those in production bioreactors. The oxygen mass transfer coefficient (k _L a) was chosen as the evaluation criterion. It is well known as an essential performance measure for fermenters in the monoclonal antibody production. Therefore a test rig was constructed able to automatically test frit-spargers with respect to their k _L a-values at various gas throughputs. Performance differences in the percent range could be detected.