LAUSR

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.