Biomass Production Potential of a Wastewater Alga Chlorella vulgaris ARC 1 under Elevated Levels of CO(2) and Temperature

The growth response of Chlorella vulgaris was studied under varying concentrations of carbon dioxide (ranging from 0.036 to 20%) and temperature (30, 40 and 50°C). The highest chlorophyll concentration (11 μg mL(–1)) and biomass (210 μg mL(–1)), which were 60 and 20 times more than that of C. vulgaris at ambient CO(2) (0.036%), were recorded at 6% CO(2) level. At 16% CO(2) level, the concentrations of chlorophyll and biomass values were comparable to those at ambient CO(2) but further increases in the CO(2) level decreased both of them. Results showed that the optimum temperature for biomass production was 30°C under elevated CO(2) (6%). Although increases in temperature above 30°C resulted in concomitant decrease in growth response, their adverse effects were significantly subdued at elevated CO(2). There were also differential responses of the alga, assessed in terms of NaH(14)CO(3) uptake and carbonic anhydrase activity, to increases in temperature at elevated CO(2). The results indicated that Chlorella vulgaris grew better at elevated CO(2) level at 30°C, albeit with lesser efficiencies at higher temperatures.