P54: A low-cost single-use photobioreactor for algal culture

The purpose of this project is to evaluate and optimize the growth of the algae strain, Tetraselmis suecica, in a small-scale, single-use photobioreactor. The project focuses on optimizing the light distribution throughout the bioreactor and the inlet flow of nutrients to achieve the highest possible growth. A single light source mimics the growth conditions of solar illumination and various reflective backgrounds are used to achieve a uniform irradiance through the reactor.  The light distribution is modeled mathematically to determine the light intensity and light distribution inside the photobioreactor. The results of the model are used to design the optimal size and shape of mirrors that are placed around the bioreactor. The inlet nutrients are varied through different medium compositions, different methods of filtering, as well as different inlet concentrations of CO₂. During the experiments the temperature is held approximately constant at 25ºC and the pH is maintained between 6 and 7 pH units. The growth is quantified with optical density measurements taken on a daily basis. The expected result of each experiment is a Tetraselmis suecica growth curve that depicts the time spent in the four phases of culture development: the lag phase, the growth phase, the stationary phase, and the death phase. Optimization focuses on decreasing the time to complete the critical first two phases of development, as well as maximizing cell concentration at the plateau.