Isolation of freshwater microalgae and outdoor cultivation using cheese whey as substrate

Abstract

The diversity and technological potential of freshwater microalgae is still poorly explored in tropical regions. The isolation and identification of these microalgae can contribute to a better knowledge of microalgal biodiversity and enables the discovery of new strains with biotechnological potential. In this work, freshwater microalgae isolated from different locations were identified and evaluated for their ability to grow in autotrophy, heterotrophy or mixotrophy. After confirming the mixotrophic capacity of the isolates, they were cultivated in cheese whey under controlled conditions. After that, the most efficient strain was cultivated in cheese whey under environmental conditions. The obtained biomass was then characterized regarding its composition of lipids, pigments, and carbohydrates. Seven microalgae were isolated corresponding to Chlorella sp., C. sorokiniana and Desmodesmus sp. All isolates showed higher growth in mixotrophy than in autotrophy or heterotrophy. Desmodesmus sp. L2B Bold, Chlorella sp. L2A Bold and Chlorella sp. L1A Bold were chosen to be cultivated in cheese whey under controlled conditions. Desmodesmus sp. L2B Bold showed the highest biomass production (8 g/L dry weight). The cultivation in cheese whey under environmental conditions allowed the production of 0.50 μg/mL carotenoids, 0.42 μg/mL chlorophyl a, 1.22 μg/mL chlorophyl b, 2.2 g/L carbohydrates, 2.37 g/L lipids and 9.97 g/L of biomass. Although the cultivation of Desmodesmus sp. L2B in cheese whey under environmental conditions has shown good results compared to BG 11, further studies are needed, for example, to evaluate the effect of scale up and environmental conditions at other seasons of the year.