Influence of power input and aeration method on mass transfer in a laboratory animal cell culture vessel

Abstract

Large‐scale animal cell operation is costly both in terms of facilities and consumables. Hence developmental studies with animal cells normally start at laboratory scale, often using small stirred tanks. In order to better optimise cell performance, it is necessary to know the physical conditions under which the cells are grown. In this study a laboratory‐scale vessel (2 dm3 working volume) with two large‐bladed paddle impellers was characterised hydrodynamically. Three different aeration methods (surface, sparging and membrane aeration) were investigated and compared. Power input and oxygen transfer rates to culture medium were determined as a function of agitation and gas flow rates. Non‐dimensional correlations were established for each case, which can be useful for scale‐up purposes. The results obtained indicate that power input is quite dependent on the vessel accessories: for the same agitation rate, the maximum power is required for the membrane structure and the minimum for surface aeration, with the addition of the sparger leading to an intermediate situation. Predictions found in the literature can be used for simple vessels, but may not be applicable when accessories are added to the vessel structure; in such cases, the use of experimental relationships are required. Oxygen transfer rate was dependent on the aeration method and working conditions (agitation and gas flow rates), particularly for sparger aeration. Membrane aeration gave larger oxygen transfer but higher gas pressure and flow rates were required. Surface aeration was the least effective method, nevertheless requiring gas flow rates similar to those used for membrane aeration. The aeration method of choice depends upon the culture and work specificities: surface aeration is limited to small cell concentrations and low oxygen consumption rates. For higher cell concentrations and oxygen consumption rates, both membrane and sparger aeration methods can be applied: the use of the sparger is limited to cells that are not affected by the presence of bubbles or the addition of surfactants, whereas the membrane aeration basket should not be used when a hydrodynamically controlled stirred tank is required.

Assessment of mass transfer and mixing in rigid lab‐scale disposable bioreactors at low power input levels

“…The power input measured for the traditional glass bioreactor, the Univessel 2L, ranges from 0.4 to 14 W m 23 at the tested impeller speeds. This is in a similar range as described previously for animal cell culture reactors 9,16 which verifies the measurement method used for power input. Power inputs for the rigid disposable vessels were subsequently determined.…”

“…On the measured data points a curve was fitted using the correlation described by Moreira et al: where K l a is volumetric mass transfer coefficient of oxygen (h −1 ), K' and α are vessel specific constants and P/V the power input (W m −3 ). The vessel specific constants ( K ' and α ) are given in Table .…”

Metabolic shifts do not influence the glycosylation patterns of a recombinant fusion protein expressed in BHK cells

“…BHK cells expressing a human IgG-IL2 fusion protein were grown in long-term continuous cultures in a 1.2-L working volume round-bottomed bioreactor (Biostat MDC, B. Braun, Melsungen, Germany), previously characterized by Moreira et al (1995). Sparger aeration was employed using air and dissolved oxygen concentration set at 15% of air saturation.…”

Shaken helical track bioreactors: Providing oxygen to high-density cultures of mammalian cells at volumes up to 1000 L by surface aeration with air

“…The usual methods for introducing gas to bioreactors include surface aeration, gas permeable membranes, and direct sparging with air or oxygen (or enriched air) [21]. For conventional stirredtank bioreactors, surface aeration was shown to be the least effective method of gas transfer compared with membrane aeration and direct sparging [22] and thus was considered adequate only for small-scale cultures. However, by combining orbital shaking with a helical track, a new type of mixing behavior was created, and a k L a value of 10 h À1 was achieved with a working volume of 1000 L even at a shaking speed of 39 rpm and surface aeration with air.…”