Towards high productivities of microalgae in photobioreactors

The biodiversity of microalgae is enormous and they represent an almost untapped source of unique algae products. Presently, there is a niche market for high-value algal products (e.g. carotenoids and fatty acids). To make commercial production of low-value bulk products possible, still many bottlenecks should be solved. This thesis addresses several of these bottlenecks. Based on research on the light conversion by the microalgae, a model was developed that predicts the minimal and maximal productivity of the microalgae in a photobioreactor. In addition, a screening method was developed for fast determination of the growth rate of microalgae. This method can be used to optimize the growth medium as well as to optimize cultivation conditions. We used this method to determine the growth inhibiting effects of free fatty acids on a microalga. In addition, the application of ultrasound as harvesting process for microalgae was investigated. It was found that ultrasound could indeed be used to harvest microalgae, but that this process was commercially only feasible for special applications on small scale. Because algal technology is a relatively new research field, learning materials should be developed for appropriate education in this field. This thesis describes the development of a practical in which third year BSc students learn how to cultivate microalgae and to develop a production strategy to achieve as much ß-carotene production as possible using these algae. Finally, the research described above is evaluated and further research strategies are identified to push microalgal technology ahead and to achieve higher productivity of microalgae in photobioreactors in the future