liquitec

bio-m®

BMAF Bottom Magnetic Agitator for Fermenters and Bioreactors

Fermentation is more than mixing: it is precise control of the micro-environment. Whether an aerobic process with high gas dispersion or a strictly anaerobic cultivation demanding complete homogeneity — the BMAF is the bottom magnetic agitator on which process stability in the fermenter rests. The series spans pilot scale to industrial production, and every project starts with pre-engineering.

N2 · N5Hub slide-on or welded
F1 · F2Can welded in or plugged in
3.1Material certificate, product contact parts

Engineering

Calculated, not estimated.

In fermentation an off-the-shelf agitator is a risk. Fit-for-purpose optimisation is therefore always part of the scope. From rheology, gassing rate (vvm) and shear sensitivity we define shaft length, impeller spacing and hub connection.

  • Pre-engineering at the start of every BMAF project
  • Critical speed calculated for each shaft and bearing reinforcement
  • Torque curve sized for the maximum aeration rate
  • Flow simulation (CFD) as an option before manufacture

Advantages

What is different in a fermenter.

Optimised parameters

Standard sizing provides a safety margin, but rarely peak efficiency. We tune impeller geometry and positioning to the process dynamics. The same result is then often achieved with a leaner drive — using less energy at lower capital cost.

Smooth running in slender vessels

Tall, slender fermenters demand long shafts in highly turbulent conditions. For every BMAF we calculate the critical speed relative to shaft dimensions and bearing reinforcement. Bearing unit and vessel bottom stay free of vibration even under aggressive agitation.

Torque under gassing

In aerobic processes the introduced gas changes fluid density and with it the load on the magnetic coupling. We calculate the torque curve for the maximum aeration rate. Mass transfer (kLa) is then limited by the biology, not by the drive train.

Impellers

Geometry follows the culture.

Rather than adapting the biology to a limited catalogue, we select the impeller by its duty in the process.

Gas dispersion

  • Disc turbine
  • Hollow blade impeller
  • Radial flow, breaks up gas bubbles for high oxygen transfer

Axial flow

  • Hydrofoil propeller
  • High efficiency impeller
  • Top-to-bottom turnover against stratification in tall vessels

Gentle cultivation

  • Marine propeller
  • Segment impeller
  • Suspension with low hydromechanical stress for shear-sensitive cells

General mixing

  • Pitched blade impeller
  • Proven for general mixing duties

Hub connection

Permanently joined or reconfigurable.

The joint between shaft and impeller governs sterility and mechanics alike. The right choice depends on whether the plant is dedicated to one process or is to be reconfigured.

  • N5, welded hub: impeller and shaft form one continuous stainless steel unit without crevices, for dedicated GMP processes
  • N2, sealed slide hub: tight-tolerance fit for mechanical rigidity, sealed against the product space with O-rings
  • With N2 impellers can be reconfigured on demand without giving up hygienic integrity

Design and documentation

Part of the GMP audit trail.

Every BMAF is supplied with a complete validation package. The flange version follows the maintenance concept.

Flange F1
Can welded into the vessel bottom, without gaskets or crevices; for dedicated lines
Flange F2
Plug-in can, removable from outside; maintenance without breaching the sterile vessel, also without hand-hole access
Material certificates
3.1 for all product contact parts
Surface
Certified surface roughness report
Delta ferrite
Verification of delta ferrite content
Seals
FDA and USP Class VI compliant
Flow simulation
CFD as an option: flow pattern, shear gradients and mixing time in the specified vessel geometry

Contact

Enquiry

For pre-engineering we need working volume, vessel geometry, gassing rate and the shear sensitivity of the culture. Tell us what you are fermenting.

Prefer to write directly?

+41 55 450 83 00 sales@liquitec.ch