Biomass yield of Isochrysis galbana (Parke; clone T-ISO) and growth of Brachionus rotundiformis (Tschugunoff) using continuous cultivation method

Abstract

Batch culture of Isochrysis galbana clone T-ISO is difficult due to its unstable biomass production; hence, the effect of continuous cultivation at different dilution rates was investigated to compare its productivity with that of batch culture. Significantly higher total algal cell yield was attained in continuous cultures (1.70 × 10⁸ and 1.03 × 10⁸ cells L^-1at 0.60 d^-1 and 0.30 d^-1 dilution rates, respectively) compared with batch culture (0.16 × 10⁸ cells L^-1); the batch culture did not receive any inflow of nutrients. The amount of protein per cell was similar in both batch and continuous cultures at 0.60 d^-1 dilution rate after 24 h and 5 d in both culture systems. Chlorophyll a yield was not affected by dilution rate but decreased as the culture aged. The dry weight yield was also similar in both batch and continuous cultures. The higher nitrate concentration supplemented in the batch culture resulted in higher cell density and elevated protein content of the alga. Rotifer (Brahionus rotundiformis) cultures that received inflow of nutrients from the algal tanks had significantly higher (P<0.05) peak population count (28 and 33 individuals mL^-1 at 0.30 and 0.60 d^-1 dilution rates, respectively) compared with rotifer cultures that did not receive an inflow of food (18.22 individuals mL^-1). The higher biomass yield of T-ISO using continuous cultivation method can increase the population growth of rotifer under tropical conditions.