Design of Experiments (DoE)
Interest in DoE has been increasing over the past few years, and the concept is now broadly used. In fermentations, DoE is being used to assess medium composition or other process parameters that influence the formation of biomass or product.
Using DoE, users get an impression of how strong influences are and if there are interactions between single factors. Also an initial impression of space-time-yield or productivity can be drawn out of these experiments. Furthermore, fermentation parameters can be optimized efficiently based on this knowledge.
Using DoE, bioprocess behavior under different conditions can be simulated. DoE software provides graphical interpretation of the investigated results and helps to predict system behavior under specific conditions. Because of the wide variety of influencing factors, it is very difficult to apply DoE plans manually. Special plans for manual pipetting of microplates are available, but they are always a compromise. Designs for manual use are limited in their variability.
As a result, the application of DoE plans in the RoboLector S was of critical importance. RoboLector Agent software is able to import whole DoE plans. Researchers have to first design their DoE plan with separate DoE software such as MODDE (Umetrics, Sweden) or others. Then, users can import the DoE plan in the RoboLector Agent software and perform the pipetting with the RoboLector S.
After the fermentation run the user can analyze the outcome of the fermentations again in the DoE software and generate response surface models. If necessary, a new DoE plan can be conducted with the RoboLector S. Again here, online monitoring of the fermentations can be beneficial for the DoE model, because the more information available, the more precise the model can be.
The application of the RoboLector S is demonstrated in an experiment with Pseudomonas putida. Here, 48 parallel fermentations were performed with variations in the available nitrogen and phosphate concentration in the culture medium. Figure 3 shows the outcome of the experiment in a 3-D surface plot. The maximum biomass concentration was reached at 100% nitrogen and 50% phosphate concentration. The same considerations can be made for product formation and with other media components.