Light and temperature requirement
The light intensity required for efficient photosynthesis of the tested microalgae
was quite low, i.e. ca 100 μmol m-2 s-1, implying that in Southern Finland there is
enough natural light for algal growth from February to October.
The algae were photosynthetically active at 10°C, but the optimum temperature
for photosynthesis of C. pyrenoidosa, E. gracilis and Selenastrum sp. was higher,
i.e. 15, 25 and 20°C, respectively. In the winter, when light would be the growth
limiting factor in autotrophic cultivations, the ability to shift from autotrophic to heterotrophic
growth could be utilised (Section 4). Either mixotrophy or heterotrophy could
be implemented to use waste carbohydrates as the organic carbon source.