Effect of Carbon dioxide (CO2) concentration on Growth of Ulva intestinalis in Photobioreactor

The alga was cultured with the initial weight of 0.05 g/L in 10 liters of modified Grund's seawater medium in total volume of 12 liters transparent polyethylene chamber under controlled conditions of 25 ppt seawater and light intensity of 80 mu mol m(-2)s(-1); and given the aeration by bubbling air with carbon dioxide at different content of 0, 1, 3 and 5% (v/v) with the flow rate at 3 L/min. Each treatment of the experiments was done in three replications for 18 days. The results showed that the growth of U. intestinalis had significantly different among the treatment (p<0.05). The final wet weights of the alga were 5.22 +/- 0.04, 6.49 +/- 0.83, 3.60 +/- 0.67, and 0.68 +/- 0.16 g/l; respectively. The relative growth rate (RGR) obtained were 2.19 +/- 0.04 % g day(-1) (for 0 % CO2), 2.31 +/- 0.07 % g day(-1) (for 1 %CO2), 1.98 +/- 0.01 % g day(-1) (for 3 %CO2) and 0.81 +/- 0.05 % g day(-1) (for 5 %CO2). This study suggested that carbon dioxide supplementary in the cultivation of U. intestinalis provides slightly increased in the production; while carbon dioxide exceeded 3 % (V/V) may inhibit the growth of this alga species.