Non-rotational mixing with “FiSH-TAIL” stirring discs

  • Vibromixer for up and down agitation in the fermentor and bioreactor (0 – 50 W)
  • No vortex formation and therefore, no baffles required
  • No rotary mechanical seals resulting in achievement of easy sterile conditions
  • Efficient mixing in horizontal and vertical direction with “FiSH-TAIL” discs
  • Shear stress free agitation
  • Optimal oxygenation and gas transfer (no air flooding) in the medium
  • Simple installation, high productivity and low maintenance costs

Why up and down agitation?

Almost all laboratory bench-top fermenters and bioreactors use circular rotation to agitate the culture medium.

Sterility: The most critical point in rotating axis stirring

The naturally existing free space between static reactor vessel wall and rotating stirring axis is difficult to seal against contamination from the outside

To limit the probability of contamination risks in conventional rotating agitator:

• Low cost lip seals or liquid seals used which requires regular maintenance and replacement
• Rotational stirring with magnetic couplings solution, very complex and expensive

LAMBDA has found a very simple, innovative solution for these agitation problems by selecting a non-rotational vertical up and down mixing solution. A simple elastic membrane allows the movement of the stirring axis and serves at the same time as a quality seal between the vessel and its central threaded cap. The membrane separates completely the interior of the vessel from the outside environment and at low cost. The problems caused by the magnetic coupling are totally eliminated here and combined with the agitation system used.

The up and down agitation produces no vortex (eddies) which eliminates the need for baffles. It spares costs, simplifies the setting up and cleaning of the fermentation vessel.

The very expensive head plates which are heavy, complicated to set up and clean are no longer needed. The cost of adapting the vessel volumes according to the experiment is much lower, as the special head plates, probes and other parts* for each vessel are not required. In the MINIFOR fermentor and bioreactor system, it is simple and easy to interchange working vessels at low cost as the same vibromixer and control unit can be used for different vessel volumes.

* Most important costs which lead many users to rather buy fermentor with the largest possible vessel volume and to work under more expensive and high volume conditions, even if it is not required.

Why to use large volume fermentors when excellent results can be obtained with much lower volume!

Bio-mimicking “FiSH-TAIL” discs

By mimicking the movement of fish tail, LAMBDA created new mixing discs for the MINIFOR fermentor and bioreactor.

The tail of fish has a perfect design which completely eliminates eddies (turbulences) in order to maximize the propulsion of the fish in water. When, in contrary, the fish tail is fixed then water will stream away with maximal efficiency.

In analogy to a fish tail, the stirring disc produces a long range movement of the liquid (culture medium) and it eliminates cutting edges and micro-eddies formed by common impellers. As a consequence, the cell viability is increased.

FiSH-TAIL bioagitation offers:

• Highly efficient and gentle mixing
• No hydrodynamic shear stress to the cells (highly beneficial for stem cells, HeLa, HEK-293, CHO and other mammalian cells)
• Good oxygenation and suboptimal gas exchange in medium

The “FiSH-TAIL” agitation discs are efficient even at very low volumes of medium in the vessel and a large portion of medium can be taken out from the vessel allowing to work well in low medium volumes. This makes the work easier – shorter sterilization and heating time, lower consumption of medium, which in turn leads to the cost effective process.

Advantages of “FiSH-TAIL” agitation

The non-rotational “FiSH-TAIL” agitation can be used advantageously for a great variety of microorganisms like bacteria, fungi, plant and animal cells. The up and down bioagitation ensures gentle (yet efficient) mixing and homogenous gas and mass transfer throughout fermentation / biotransformation.

Types of stirring discs:

• Standard “FiSH-TAIL” stirrer discs: mammalian cells, plant cells, fungi, bacteria and yeast
• Metal stirrer discs: viscous medium
• Butterfly-shaped stirrer discs: low working volume (for example: 35 ml)


Optimize the agitation:

• Type of the stirring discs

• Number of stirring discs

• Frequency of stirring (0 – 1200 rpm)

The number and position of the FiSH-TAIL stirring discs can be adapted to any working volume in the vessel.

The material and hardness of the stirring discs vary from soft FiSH-TAIL discs for shear sensitive cells to perforated plates for viscous media.


Homogeneous and efficient mixing of shear sensitive stem cells, HeLa, CHO and other mammalian cell lines.

Complete physical closure of the vessel eliminating frequent contaminations.

Vibromixer with the elastic and durable membrane maintains long-term sterility (no contamination prone rotary axis) and reliable as expensive magnetic coupling.

Easy and quick to interchange working volumes (35 ml to 6 L).


Controlled morphology of submerged fungal culture, mycelium (filamentous mycelia, dispersed mycelia), spores, conidia and pellets in the culture broth or media.

Up and down agitation without vortex formation eliminates the need for the baffles (vortex breaker).

Homogeneous distribution of fungal culture is achieved instead of the cells getting trapped between the vessel walls and baffles (no niche places for inhomogeneous fungal growth).