Evaluation of Cultivation Parameters Effects on Pigments and Carbohydrates Production by Arthrospira platensis

Introduction: Arthrospira platensis is a microalga of great pharmacological and alimentary value due to rapid growth and high productivity of several compounds as proteins, carbohydrates, carotenoids and the phycocyanin pigment, which have a broad spectrum of biological activities.1,2. It is know that photon flux density (PFD) and nitrate concentration may cause a metabolic stress and affect the pigments and carbohydrate production by A. platensis.2,3 However, studies of the effect of the variations of PFD and nitrate concentrations in simultaneous carbohydrate and pigments production were still not carried out. Objective: To evaluate the production of pigments and carbohydrates in different cultivation conditions of PFD and nitrate concentration in A. platensis. Methodology: A. platensis was cultivated in Zarrouk medium with different NaNO3 concentrations (0.25, 1.125 and 2 g.L-1) in bottles (4 L) at 32°C under constant aeration, and under white LED of different PFD (200, 600 and 1000 μEm−2s−1). The carotenoids extraction and quantification was performed according to the methods performed by Lima et al.2The phycobiliproteins were extracted by the freezing/thawing method and quantified using the equation defined by Bennett and Bogorad (1973).4,5 Carbohydrate quantification was carried out according to Dubois et al. (1956).6 Results and Discussion: The greatest carbohydrate concentration (131.63 ± 10.85 mg.L-1) was observed on 0.25 g.L-1 and 1000 μEm−2s−1, the lowest NaNO3 concentration and the highest PFD value, respectively. Lowest nitrogen concentrations can affect the carbohydrate production, since in the starved nitrogen condition metabolism will be directed to the production of reserve compounds such as carbohydrates. Previous studies have reported that phycocyanin production is more effective at lower PFD4; this result was also observed in this study, as the lowest PFD of 200 μEm−2s−1 showed to be the most effective in the production of phycocyanin (82.52 ± 1.01 mg/g). In addition, the NaNO3 concentration of 1.125 g.L-1 was the most effective at this PFD for phycocyanin production, showing that there is a minimum of NaNO3 concentration to reach a certain phycocyanin content and an additional quantity of NaNO3 does not influence this production. The quantification of total carotenoids showed that high PFDs (600 and 1000 μEm−2s−1) and the low concentration of NaNO3 (0.25 g.L-1) were the best condition to produce these substances (0.074 ± 2.10 mg.g-1). Conclusion: The lower PFD and median NaNO3 concentration stimulates the phycocyanin biosynthesis. On the other hand, the high PFD and low NaNO3 concentration increases the carotenoids and carbohydrates production. References: 1Cavalcanti et al., Produção e Controle de Produtos Naturais, Ed. Atena, cap. 6, 2018 2Lima et al., Influence of spectral light quality on the pigment concentrations and biomass productivity of Arthrospira platensis, Algal Research, 31, 157-166, 2018. 3Sujatha & Nagarajan., Effect of different nitrogen concentrations on the biomass and biochemical consituents of Spirulina platensis [Geitler], Asian Journal of Bio Science, 8.(2), 245-247, 2013.4Cavalcanti et al. Production of Pigments with Commercial Interest Obtained from Arthrospira platensis grown in two different LEDS, 42ª Reunião Anual da Sociedade Brasileira de Química, 2019. 5 Bennett & Bogorad, Complementary chromatic adaptation in a filamentous blue-green alga, J Cell Biology 58(2), 419-435, 1973.6Dubois, M., Gilles K. A., Hamilton, J. K., Rebers, P. A., Smith, F. Colorimetric Method for Determination of Sugars and Related Substances. Analytical Chemistry 28 (3), 350-356, 1956.