Abstract

Growth studies were conducted on green algae Chlorella, Scenedesmus andHaematococcus strains in batch mode cultures. In this study, the effect of sodium bicarbonate salt (NaHCO₃) and carbon dioxide (CO₂) gas as carbon source on microalgal cultures were investigated. For this purpose, growth response of theaforementioned three strains under varying concentrations of NaHCO₃ (15, 30, 45, 60 and 75 mg/L,) and CO₂ gas (7929, 4758 and 4400 mg/L,) were investigated. The best growth response showed by chlorella strain was observed at 75 mg/L (ppm) bicarbonate (% increase in biomass=82.6mg/L/day for 12 days) and 4758 mg/L CO₂ gas concentration (189.1 mg/L/day for 7 days). While Haematococcus strain showed its best growth in 30 ppm bicarbonate (72.9 mg/L/day for 17 days) and 4758 mg/L CO₂ gas (134.1 mg/L for 7 days), the Scenedesmus strain showed its best growth in 45 ppm bicarbonate (30.9 mg/L/day for 17 days) and 4758 mg/L CO₂gas (103.8 mg/L for 7 days). All the strains showed good growth when CO₂ gas was supplied in terms of increase in cell number, biomass and lipid content compared to bicarbonate utilization as carbon source, except Haematococcusstrain which fail to grow when high concentration of CO₂ gas (7929 ppm) was supplied. Out of the three strains, it was Chlorella sp. which showed highest growth rate and lipid content when CO₂ gas was supplied, (specific growth=0.704; 189.1% increase in biomass, g/L/day  and 1.015 doubling/day, 31% lipid content in terms of dry cell weight).

Key words: Microalgae, bicarbonate, biomass, lipid.

Abbreviation

CA, Carbonic anhydrase; DIC, dissolved inorganic carbon.