The effect of different environmental conditions on the growth rate, biomass production, nutrient composition, and phenolic content of the microalgae species Chlorella vulgaris, Botryococcus braunii, Chlamydomonas reinhardtii, Euglena gracilis, and Nannochloropsis oculata was investigated. The experiments were conducted in open bioreactors in a greenhouse in three different periods (during October, March, and June), and in a controlled environment in a closed plant growth chamber. It was found that the growth rate and production of C. vulgaris and B. braunii was higher during March, C. reinhardtii and N. oculata grew better in June, and the growth of E. gracilis was similar in March and June. The lipid content of the biomass of all five species increased with increasing light intensity and temperature, while the nitrogen free extractable (NFE) content decreased and the protein, fiber, moisture, and ash content remained relatively unaffected. The phenolic content varied from species to species with E. gracilis having the highest and N. oculata the lowest content among the species studied. The results can be taken into account when cultivating the different microalgae studied in full scale applications, such as in open raceway bioreactors, where conditions could be adjusted to obtain the most favorable growth conditions, depending on the particular species cultivated.
Keywords: Chlorella vulgaris; biomass production; growth chamber; light intensity; nutrient content; seasonal growth; temperature.