Optimal experimental design is an area of statistics focused on constructing informative experiments. In this tutorial we introduce the necessary tools to construct such informative experiments for dynamic systems using only 100 lines of Julia code. We will work with a well-mixed fed-batch bioreactor as an example system. We have quite a bit of domain knowledge how to model the behavior of such a reactor. The reactor has three dynamic states: the substrate concentration \(C_s\), the biomass concentration \(C_x\) and the volume of the reactor \(V\). The evolution in time of these states is governed by the following differential equations: