Design an Experiment on Cell Growth

Below is a description for the module Design of experiments on microbial growth in which students repeatedly design and perform experiments to obtain data that will allow them to estimate cell-growth parameters.

The contents of this module have been described in:

  • O.D.T. Sessink, H.H. Beeftink, R.J.M. Hartog and J. Tramper (2006). Virtual parameter-estimation experiments in Bioprocess-Engineering education. Bioproc.Biosys.Eng., in press.

Requirements

The module opens in a new window when started; it might be convenient to print this page for reference (see page bottom). The demo requires a recent browser (Mozilla, Opera or Internet explorer) with Flash plugin and Java plugin.

Start the Experiment-design module

(use Ctrl-Click if needed)

Tour description

The growth module focuses on the design of experiments to measure parameters in standard models for cell growth, like the Monod model and the Linear growth and maintenance model. The models are applied in several reactor systems like batch and CSTR reactors.

This module is used after students have had lectures about these models and these reactors, and after they have had several working lectures where they apply the theory on simple problems. The problem given to the students in this module is quite complex.

This module is a virtual experiment. In most practical courses the focus is on the practical skills, and the calculation of values from the data. In those practicals, there is no option to really design experiments, run those designs, learn from the data what was wrong in the design, design a new experiment etc. There is simply not enough time and resources to do this. These virtual experiments do focus on these parts, there are no practical skills involved.

  • On the right top there is a navigation box. Click Introduction to batch cultivation. A new window will open.

Before students start with the experiments, they can have another look at the system they will be working with. This presentation is there to refresh the names of all the symbols, and the way they change over time in a typical batch cultivation.

  • Close the window with the animation, and now find the link Start the experiment here in the middle of the page. A page with a large java applet will start. It is possible you get a warning window from the java plugin. Click Always in this popup window.

In the first view of the virtual experiment the students get their assignment. Eevery student will get a different assignment. To solve the assignment they have to design several experiments, run them, validate them, and (if valid) calculate the required parameters. These experiments cost money. The smarter they setup their experiments, the cheaper they will solve the assignment.

  • Click Start new experiment on the right side of the java applet. A new window will open.

In this window the initial settings for this experiment can be set, and the experiment can be run. The students will face their first problems here. They have to give biomass and substrate concentrations, but what are realistic concentrations? Is a million kg/m3 realistic? Or should it be 1E-9 kg/m3? And what should they start with anyway to find useful data?

  • Use the following settings for the first experiment:
        initial biomass concentration: 0.1
        initial substrate concentration: 20
        initial product concentration: 0
        choose batch

  • Now click the Run & Results tab in the bottom right of the experiment window.

This is where you can run an experiment. You can set when you want to take the next sample, and you can choose which type of analysis you want for this sample.

  • Take the next sample in 1 hour, click Go!. Continue this several times.

In the graphs and in the table you can now see the results from the experiment. As you can see there is some noise in the measured data. So the students have to do proper statistical analysis to get accurate values for the parameters. You can also see the costs from this experiment.

  • Close this window, and now click the Test your answer button. A new window will open.

In this window the students can test the values they have found, and they will get some feedback about those values. If the answer was correct, the current costs are stored in the highscore table.

  • Close this window.

This is the end of the Growth Module demo. Feel free to explore other pages not part of this demo tour, or to really try a realistic experiment.