kLa Measuring

Characterization of Bioreactor Systems for their Oxygen Transfer Rate

Special focus on measurement of the mass transfer coefficient kLa

Bioreactors are expected to provide optimum conditions for growth and product formation of microorganisms or the cell culture with the aim of maximising product yield.

The oxygen transfer rate (OTR), and the kLa value in particular, are the decisive parameters for the design of bioreactors.  The volumetric mass transfer coefficient kLa is used as the efficiency ratio of the transport of a gas from the gaseous phase to the liquid phase. In biotechnological processes, the kLa coefficient indicates the efficiency of oxygen supply to microorganisms in a bioreactor.

Possible measures to increase the kLa value under gentle process conditions, which will in turn improve the overall performance of the organic process, include for example: increased agitator speed and gassing rate, optimisation of fermenter and agitator geometry, enlarging the phase boundary (e.g. by aeration with finer gas bubbles) or optimisation of the media composition.

What ZETA Does

Since the kLa value depends on numerous factors, it cannot be precisely calculated but needs to be determined by means of kLa measurement at critical process points. ZETA provides a best-in-class measuring methode to enable QbD principles:

  • Measurement of any point in the fermenter 
  • No structural changes of fermenter required 
  • Bubble separation prior to measurement for optimum   measurement result 
  • Optical high-speed oxygen sensors with response times of < 0.5 sec

The following services are provided by ZETA Experts:

Characterisation of fermenters 

  • Measurement on site at the customer premises 
  • Analysis of data and results 
  • Customer briefing 
  • Development of scale-down models

Optimisation of installed process systems

  • Operational parameters 
  • Retrofitting: Agitator design – sparger design

Designing and planning the optimum fermenter 

  • Pilot testing at the ZETA technical centre including scale-up calculations 
  • Specification and design of agitation systems in line with the process  
  • Customised solutions for individual processes feature

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