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RSSLarge-Scale Disposable Shaking Bioreactors: A Promising Choice
January 12, 2009
Click Here To Download:•Feature Article: Large-Scale Disposable Bioreactors: A Promising Choice
By Keyur Raval, Chao-Min Liu, and Jochen Buchs, BioProcess International
Vessels are made of polypropylene or from transparent polycarbonate. The machine has a maximum loading capacity of 200 kg, with shaking frequencies from 20 to 400 rpm. Each vessel has a largediameter closure (not mounted on the right vessel in Photo 1) to ensure easy mounting of disposable air inlet, outlet, and sample ports. A normal electrochemical dissolved oxygen electrode can be mounted on the closure. Use of optical sensors for pH and dissolved oxygen (PreSens GmbH, Germany; External Web site ) can leave more space on the closure.
Mixing Performance
Cell culture systems are sensitive to concentration, pH, and temperature gradients. These gradients may appear because of nonhomogeneous or generally poor mixing. Bioreactors used for animal and plant cell cultures must therefore possess good mixing characteristics without generating large hydromechanical stresses. The mixing performance of a disposable shaking reactor was measured by an electrical conductivity method. A tracer of 0.5 mL of 1M sodium chloride was added to the vessel at steady state, after which the electrical conductivity of the liquid was measured. The mixing time was defined as that for 99% of the total change in concentration following addition of the tracer. Figure 1 shows the mixing time of 20-L and 50-L vessels at 15-L and 35-L working volumes, respectively. As the figure depicts, for shaking frequencies larger than 80 rpm, mixing occurs only a few seconds after addition of the tracer. Although mixing also occurs at frequencies lower than 80 rpm, it is not recommended to operate under these conditions because no regular liquid flow pattern is observed (1). Power consumption is an important characteristic of a reactor's performance. The magnitude of hydromechanical stress depends on the magnitude of power consumption. The power consumption in 20-L and 50-L vessels was measured using the temperature method developed by Sumino et al. (2). Results show that the order of magnitude of power consumption obtained is almost the same as that obtained in small shake flasks (3). Power consumption is more evenly distributed in shake mixing than in stirred mixing (4), thus resulting in very low levels of hydromechanical stress. Click Here To Download:•Feature Article: Large-Scale Disposable Bioreactors: A Promising Choice
