Oxygen and pH monitoring in shake flasks (Erlenmeyer flask)

Software

The SFR Software SFRS is the integrated control center for the SFR Shake Flask Reader. In addition, it offers an integrated database to show and evaluate measurements. The connection between PC and SFR is wireless. Oxygen and pH are visualized in real-time during the entire cultivation. Results are displayed in a variety of graphical representations. All measured data can be exported to Excel® or as .csv for further evaluation. In addition, the current measurement can be compared to stored cultivations online.

Benefits

• Enables process monitoring in shake flasks
• Systematic optimization of cultivation parameters
• Reliable comparison of screening results
• Enhanced culture quality and efficiency
• Real-time data acquisition
• Compliant with FDA 21 CRF part 11
• Compatible with established protocols
• Supports finding feeding points
• Facilitates optimization of harvesting strategies

The Smart Measurement Method

The sensor spots are fixed at the bottom of the shake flasks. The luminescence of the dyes embedded in these sensor spots is excited by the Shake Flask Reader. The luminescence lifetime is detected non-invasively through the transparent flask. The luminescence lifetime of the sensor dye depends on the oxygen partial pressure and the pH of the sample, respectively. It is converted to oxygen and pH values by the software using the provided calibration data and internally stored conversion formula.

Yeast & E. coli: Ensure Enough Oxygen Supply

S. cerevisiae grows on different sugars as carbon source. While growth on glucose and fructose is mainly fermentative, growth on galactose is mainly respirative. This leads to low oxygen concentration in the shake flasks. The accurately measured oxygen indicates the need to increase rotation frequency to avoid oxygen limitation.

High oxygen demand is typical for E. coli in its exponential phase. In the cultivation shown on the left, rotation speed had to be changed twice in order to avoid oxygen limitation. In addition, changes in the metabolism can be detected by measuring DO.

Schneider et al., University of Saarland, Saarbrücken, Germany
Bioprocess Biosyst Eng., 33(5), 541 - 547, 2009

Process Monitoring in Suspension-Adapted CHO Cell Cultures

The online measurement of dissolved oxygen concentration and pH in shaken bioreactors paves the way for proper scale down activities from bench-top stirred-tanks to smaller scales. Adjustment of shaking speed as a function of pO₂ is now possible avoiding possible oxygen limitations at high cell densities. Even a simple pH readjustment by tuning the pCO₂ in the incubator is feasible to optimize the output from simple experiments with shaken bioreactors.
Dr. Robert Puskeiler, Roche Diagnostics, Penzberg, Germany

Improved quality control during cultivation of CHO

Cell cultivation is typically done at elevated CO₂ levels. A constant CO₂ level of 5 % is often applied to CHO cultures. An on-line pH profile measured with SFR is shown on the left. In this busy lab the incubation shaker was also used for other experiments during the cultivation of eight days. At day time closing and opening of the shaker door changed the pH significantly. SFR clearly indicates the loss of CO₂ which leads to increased pH values. SFR is the tool to ensure defined cultivation conditions leading to more reproducible results.

Prof. Thomas Noll, Stefan Northoff, University Bielefeld, Bielefeld, Germany

Systematic Determination of Oxygen Uptake in Shake Flasks

Oxygen supply is crucial for almost all cultivations. In shake flasks for a given geometry oxygen transfer is dependent on the shaking frequency and the filling volume. The contour plot on the left shows oxygen transfer rates in 250 ml plastic shake flasks. By using a software for statistical design of experiments discrete volume and rotation speed combinations were measured. As a result it is possible to determine the kLa values for the typical working range for microbial and cell cultivations.

Ries et al., ZHAW, Wädenswil, Switzerland
Eng. Life Sci 10, No. 1, 75 - 79, 2010