BACKGROUNDArthrospira platensis produces the blue pigment C-phycocyanin (C-PC) and extracellular polymeric substances (EPS) of potential value in food and pharmaceutical applications. RESULTSBatch cultures were used to simultaneously produce C-PC and EPS. The effects of incident light level on growth and product formation are reported. A maximum biomass concentration of 1.5 g L-1 in 14 days was obtained at a light intensity of 203 mu mol m(-2) s(-1). The light intensity affected the biomass composition and the production of the two products. Protein, phenolic compounds and chlorophyll a in the biomass were reduced at high light levels, but carbohydrate and the total carotenoids were increased. Production of C-PC was growth associated. The highest concentration of C-PC in the culture broth was approximate to 60 mg L-1 at a photon flux of 135 mu mol m(-2) s(-1). EPS was produced mostly in the stationary phase. The highest EPS concentration of approximate to 960 mg L-1 occurred at a photon flux of 203 mu mol m(-2) s(-1). Incident light level also affected the antioxidant properties of the two products. CONCLUSIONIncident light strongly affected the production of C-PC, EPS and the biomass composition. Low light favored C-PC production whereas high light favored the production of EPS. (c) 2017 Society of Chemical Industry