Microalgae are normally cultivated as plants, harvesting the energy of sunlight, taking up carbon dioxide (CO2) and producing oxygen (O2) as a by-product. This is called autotrophic growth. But some species can also grow heterotrophically, in a process where instead of using sunlight and CO2 as a source of energy and nutrients, they use sugar or other organic compounds together with O2 and produce CO2 in return.

Both these cultivation methods have advantages and disadvantages that limit their industrial application. For example, microalgae that grow autotrophically have low production rates, limiting their large-scale production. In turn, industrial production of heterotrophic microalgae improves production rates but is limited to a few species and more nutrients are wasted.

As so, researchers at Wageningen University (WU) are combining the best of both worlds by developing a mixotrophic growth strategy. In this process, microalgae are provided with light and an organic compounds simultaneously in a balanced manner.

This production strategy helps to overcome the low production rates of autotrophic cultivation, while reducing the nutrient waste (in this case, sugar) associated with heterotrophic growth. Because O2 and CO2 are both consumed and produced by the microalgae themselves, there’s no need to provide them externally, which simplifies the construction of the production system and saves energy costs.

ProFuture is now working on ways to take this innovative concept out of the lab into the production factories. For example, researchers need now to adapt how organic carbon (nutrients) can be fed to the microalgae in large-scale production, considering that industrial production systems are more complex. Plus, they also need to account for the possible impacts of outdoor conditions, such as the day/night cycles and changes in light and temperatures, which all directly influence the growth of microalgae.

Researchers at WU are now investigating possible solutions to each one of these challenges under controlled conditions in the lab. The investigation results will then be used to design a successful mixotrophic strategy that will be tested and validated at pilot-scale industrial setting at Wageningen University.

Stay tuned for more news!