Fig. 4

The 3-dimensional response surface plot for effects. (a) ammonium chloride and urea, (b) sodium nitrate and ammonium chloride, (c) sodium nitrate and urea concentration as well as their interaction effect on (I) phycocyanin production by Synechocystis sp. PCC 6803. (II) Predicted vs. actual value for (a) chlorophyll a (b) carotenoid (c) phycocyanin production from Synechocystis sp. PCC 6803