The Soft – Gentle mixing with rockers
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Rocking, linear or orbital shaking – three different agitation modes all with the same purpose to mix samples. Still, there are differences in the technology behind as well as in the related instruments in the lab. Learn more about the shaking processes and its applications in the lab.
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Shakers agitation modes range from slow rocking in a 2- or 3-D plane over figure-eight, up to a back- and-forth linear or orbital motion. Common to all of them is to move a top mounted platform in a certain way with the purpose to put the liquid in the vessels in motion. As shakers are used in the lab for a variety of applications from chemical extractions, over washing and staining procedures up to cell expansion, different shaker types developed over time. Not all types are equally suited for all applications.
Shakers have been used to cultivate cells since the beginning of the last century. No matter if it is a microbial, algae or mammalian shake culture, the purpose of shaking is to increase the availability for nutrients and to improve the oxygen transfer to gain a higher biomass compared to static incubation. Beside that results should be reproducible to make parallel experiments comparable. What mode of agitation is best suited for cell expansion and what mode is more appropriate for applications in molecular biology?
The Soft – Gentle mixing with rockers
Rockers move the platform either in a two or in a three-dimensional see-saw motion about the central point and usually run at low rpms < 100 rpm. They create a wave-like mixing process and are used – generally as benchtop devices – for gentle mixing and incubation procedures e.g. in molecular biological applications, like DNA extractions, staining and de-staining and washing procedures of blots and gels. In terms of cell cultivation specifically constructed rocking devices evolved allowing the cultivation of mammalian cells in single-use bags.
The Turbulent - Breaking the waves with reciprocating shakers
Reciprocating or linear motion shakers move the liquid back-and-forth in a horizontal plane. During reciprocating shaking, fluids movement starts with a surge and usually develops into a return curl before ending up in a swirl. This return curl pattern is strongly affected by liquid viscosity. It may get quite turbulent and easily inconsistent depending on fill level and speed. During speed ramp-up unpredictable geyser like eruptions which may wet the flask’s closure can occur and lead to culture contamination and decrease in aeration . Due to these limitations, reciprocating shakers have been mostly vanished from the labs for cell cultivation. Their application focus moved to molecular biology and chemical applications e.g. for (de)staining of gels, washing blots, solubility studies or mixing of separatory flasks and funnels in chemical extractions.
The Consistent – Continuous swirl with orbital shakers
Nowadays most of the shakers for cell expansion of microbial, algae, and mammalian cultures are orbital shakers. Orbital shakers rotate the platform in a circular motion, which results in a consistent “swirl” pattern. In comparison to reciprocating shakers, the swirl pattern formation is much less affected by variables like media viscosity, instrument ramp-up or fill volumes . It is also well suited for shear sensitive cells. An even and consistent distribution of the liquid is a prerequisite to make parallel experiments comparable. For this reason, orbital shakers are the preferred shakers for cultivation of microorganisms and cells. Orbital shakers are nowadays also available with temperature control and other options like e.g. photosynthetic lights or CO2 control to meet specific culture demands. Typical applications are cell expansion for plasmid or protein expression, media development, screening and inoculum preparation. Almost all recent studies about the culture of microorganisms are performed in orbital shakers.
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