Flow INTEGRATOR reveals valuable culture information

Frequently scientists want to know how their culture grows and what its metabolic activity during biotransformation is. For that reason, they are looking for instruments which can measure the optical density (OD) of the culture.

What is Optical Density (OD)?

Optical density is a logarithmic function and increasing the number of light absorption unit by one means that the intensity of light passing through the sample has diminished 10 times!

No need to say that at an optical density of merely 4 the light intensity has decreased by a factor of 10,000. It is a demanding task for electronics to measure such a low signal with precision. And what about OD 20 or 100?

Even though many devices for the measurement of optical density of culture broths have been presented, none is really satisfactory.

Why OD measurement is not precise?

• It also measures dead cells and cell debris. If many dead cells are present in the culture, the resulting metabolic activity will be wrong.
• Also small air bubbles are measured and counted as living cells! The number of microscopic air bubbles, especially in dense cultures, may be quite high.
• Needless to say, any precipitate or coloration formed during the culture will distort the estimation of metabolic activity of the measured culture.

What INTEGRATOR does?

What is really needed is a parameter which could easily be measured and would allow the estimation of the metabolic activity of living cells.

With the pump flow INTEGRATOR LAMBDA proposes such a possibility:

The metabolism of all living organisms is somehow connected with the production or consumption of acids or bases. This can be measured and put in relation with cell growth or other metabolic activity. The metabolic activity results then in the change of pH value, which is automatically corrected by the addition of acid or base to remain on the preset pH value.

Normally, the amount of required correction solution is not known beforehand.

The LAMBDA INTEGRATOR allows visualizing the amounts of acid or basis added as a function of time. The concentration of acid or base is known and from the data obtained by the INTEGRATOR.  The added amount of acid or base can be calculated with analytical precision. Thus, the metabolic activity can be calculated with much better precision than from difficult OD measurement.

Since the cost of the INTEGRATOR is at least twenty times lower, the economy for the laboratory is considerable.

Enclosed is one example of the trace of an acid pump activity transformed by the INTEGRATOR during one biotransformation culture (red trace with two resets). The red trace is the only one which is clearly exponential, as it should be. By totalizing the consumption of acid, the extent of transformation and the immediate state of the culture can be derived. No need to say how important such information can be for the control and reproducibility of different cultures.

Clients of LAMBDA are so convinced about the usefulness of the INTEGRATOR, that they put INTEGRATORs on almost any controlled parameter. No wonder, cells are so complicated that any additional information can only be beneficial.