Every wine aficionado knows that wine has to be swirled in a glass in order for it to release its aroma. Applied to biotechnologies over some fifteen years, this ordinary gesture has made it possible to develop more efficient machines for culturing proteins in animal cells. The phenomenon has been studied in detail.
First, slowly pour. Then sniff. Then, keeping the base of the glass anchored, apply a very light circular movement. Inhale again. Start over, each time swirling the glass a little more strongly to aerate the wine. This is how one goes about appreciating the complex bouquet of a fine vintage.
Nobody’s contesting the legitimacy of this protocol; it’s something that everyone just does more or less intuitively when presented with a grand cru or a cup of coffee without a spoon. But as for precisely explaining the fluid mechanics involved in this operation, known as “orbital agitation,” – well, that’s another story!
Orbiting bioreactors
Professor Florian Wurm at EPFL has been developing bioreactors that work on this principle for many years, based on the intuitive understanding that orbital agitation results in a mixing action that is both gentle and effective. The spin-off company that he has created to use reactors of this type, ExcellGene, has just celebrated its tenth anniversary. “We now are using small as well as large volume machines, to manufacture high value recombinant proteins in animal cells,” he announces. “Most recently, in collaboration with Kühner AG, the EPFL and the ExcellGene, one of the world’s largest bioreactors based on orbital shaking has been constructed, with a total volume of more than 3000 Liters.”
In traditional bioreactors, the contents are mixed by a rotating platform that sits underneath a container. By replacing these with orbital shakers (in which the entire tank is moved), Wurm says he is able to significantly reduce the cost of manufacturing proteins, which are used widely in the pharmaceutical industry. “The cultured cells receive fewer shocks, the mixture is more homogeneous, it can be done in a normal air rather that in pure oxygen, and this technique allows us to construct wider and shorter bioreactors, that are thus easier to install in rooms of standard dimension, he adds. Moreover, we now use disposable plastic bags inside the reactor, which cut most of the maintenance costs.”
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