Arthrospira platensis is a non toxic edible cyanobacterium which 
contains high amounts of various valuable nutrients such as essential 
amino acids, essential fatty acids and carotenoids. It also contains 
compounds having medicinal effects, such as phycocyanin and 
different polysaccharides. The present study examined the effect of 
nitrogen, phosphorus, sulfur and salinity on biomass, lipid, protein, 
carbohydrate and phycocyanin productivities of Arthrospira platensis. 
Decreasing nitrogen to 50 % than the concentration mentioned in the 
modified Zarrouk medium resulted in a reduction of biomass, lipid, 
protein, carotenoids and phycocyanin productivities by 20, 12, 20, 2 
and 32 %, respectively. While 100 % phosphorus deficiency enhanced 
lipids and carotenoids productivities by 128 % and 64 %, respectively, 
with 25 % reduction in biomass. In addition, sulfur limitation led to 
280 % increase in carbohydrate productivity with insignificant 
changes in biomass productivity. Finally, increasing salinity caused 
significant increase of lipid, carbohydrate and carotenoids 
productivities up to 93, 84 and 64 %, respectively. Whereas, 
increasing salt concentration, increased lipid and carotenoid 
productivities. The present study showed that phosphorus and sulfur 
deficiencies and high salinity increased the productivity of some 
valuable products of Arthrospira platensis. Therefore alteration of 
growth conditions changes its nutritional compounds. This means that 
we could obtain Arthrospira with different nutritional composition by 
altering the composition of cultivation medium.