An important way to decrease the costs of microalgae and cyanobacteria production is by increasing the production rate of biomass and products in a photobioreactor. This can be done either by optimizing the operation strategy of the bioreactor or improving the design of the photobioreactor. Both will have
implication for scale up. The productivity gain therefore must be carefully balanced with potential higher (energy) costs of reactor construction and operation.
Optimizing microalgae growth
At AlgaePARC the relation between microalgae growth and the most relevant cultivation conditions are studied in detail. Special emphasis is given to the supply of light and CO2, and removal of O2. Considering the fact that sunlight cannot be controlled and is limited we strive for a most efficient use of sunlight. As such, we study the effect of light attenuation and thus biomass density on photobioreactor productivity. In addition, we explore possibilities to dilute strong sunlight, and thereby increasing light use efficiency. The latter theoretically can more than double light use efficiency but light dilution. The influence of fluctuating light in microalgae culture due to mixing of microalgae over the internal light gradient is another aspect which we study at AlgaePARC. Accumulation of O2 can severely inhibit microalgae growth, while a limited supply of CO2 limits growth. Based on these biological limitations we can select appropriate O2 and CO2 levels for microalgae productions systems. Also here we need to carefully balance the benefits (higher productivity) versus higher costs (including energy) maintaining these O2 and CO2 levels in large-scale outdoor photobioreactors (see scale-up).
Optimizing microalgae product formation
To increase the yields of microalgal products such as lipids, proteins, carbohydrates and pigments, it is important to understand the effect of cultivation conditions on product formation. In close collaboration with our experts on cellular processes we get to know the needs of our strains while grown in lab scale photobioreactors. Based on our understanding of the relation between cultivation conditions and cell physiology, the optimal conditions for product formation are determined. Subsequently, outdoor growth conditions can be simulated, to find be able to find the most promising growth strategies for product formation. These growth strategies can be further optimized at the pilot facility.