Induced change in Arthrospira sp. (Spirulina) intracellular and extracellular metabolites using multifactor stress combination approach

The interactive effects of light intensity, NaCl, nitrogen, and phosphorus on intracellular biomass content and extracellular polymeric substance production were assessed for Arthrospira sp. (Spirulina) in a two-phase culture process using principal component analysis and central composite face design. Under high light intensity (120 μmol photons m−2 s−1) and low NaCl (1 gL−1), NaNO3, and K2HPO4 (0.5 g L−1), the carbohydrate content was maximized to 26.61%. Interaction of both K2HPO4 (1.6 gL−1) and NaCl (1.19 gL−1) with low NaNO3 (0.5 gL−1) achieved the maximum content of lipids (15.62%), while high NaCl (40 gL−1), K2HPO4, and NaNO3 (4.5 gL−1) enhanced mainly total carotenoids (0.85%). Conversely, under low light intensity of 10 μmol photons m−2 s−1 combined with 11.76 gL−1 of NaCl, 0.5 gL−1 of NaNO3, and 2.68 gL−1 of K2HPO4, the phycobiliprotein content reached its highest level (16.09%). The maximum extracellular polymeric substance (EPS) production (0.902 gg−1 DW) was triggered under moderate light of 57.25 μmol photons m−2 s−1 and interaction of high NaCl (40 gL−1) and K2HPO4 (4.5 gL−1) with low NaNO3 (0.5 gL−1). The maximization ratios of intracellular biomass content in terms of carbohydrate, lipid, total carotenoid, phycobiliprotein, and EPS production were 3.55-, 1.73-, 9.55-, 2.92-, and 1.46-fold, respectively, greater than those obtained at optimal growth conditions. This study demonstrated that the multiple stress factors applied to the adopted two-phase culture process could be a promising strategy to produce biomass enriched in various high-value compound.