Comparison of growth, protein and carotenoid contents of some freshwater microalgae and the effects of urea and cultivation in a photobioreactor with reflective broth circulation guide on Desmodesmus subspicatus LC172266

This study assessed the potential of enhancing carotenoids and protein accumulation by Desmodesmus subspicatus LC172266 by urea supplementation and cultivation in a novel flat plate air-lift photobioreactor with broth circulation guides. Addition of 0.2 g L−1 urea to BG11 medium significantly increased the cell growth in both flask and photobioreactor cultures. Carotenoid accumulation by D. subspicatus was about 5.7 times (15.5 ± 0.1 mgg cell−1) higher in the photobioreactor with reflective broth circulation guide than in the flask culture (2.3 ± 0.1 mgg−1 cell) and about 46% higher than the carotenoid content obtained in the photobioreactor without broth circulation guide (control).The cell growth rate was about 2 times higher in the photobioreactor with reflective broth circulation guide (0.41 ± 0.005 day−1) than in flask culture (0.20 day−1), and in the control photobioreactor (0.28 day−1).Both the protein contents and biomass concentrations were significantly enhanced by cultivation in the novel photobioreactor. This research has demonstrated that the flat plate air-lift photobioreactor installed with reflective broth circulation guide substantially enhanced carotenoid production by D. subspicatus LC172266.