Sodium Bicarbonate as Inorganic Carbon Source for Higher Biomass and Lipid Production Integrated Carbon Capture in Chlorella vulgaris

Chlorella vulgaris was isolated from sewerage treatment plant and grown in the presence of sodium bicarbonate as carbon source at 0.25, 0.5 and 1.0 g L^− 1. Highest specific growth rate (0.653 μ d^− 1) was obtained with 1 g L^− 1 bicarbonate followed by 0.5 g L^− 1 (0.641 d^− 1) on 15th day culturing. Total chlorophyll content of microalgae has increased in a dose dependent fashion with bicarbonate addition and maximum level recorded in 1 g L^− 1 (0.769 ± 0.09 g L^− 1). The biomass productivity was in the range of 0.237–0.996 g d^− 1 L^− 1. Rate of CO₂ fixation and carbon content, in terms of quantity was estimated. Results showed that at 1 g L^− 1 sodium bicarbonate concentration, maximum CO₂ fixation (0.497 g/dry weight) and carbon content (0.69 g mL^− 1 day^− 1) was found. Biomass concentration was significantly higher (p < 0.05) in cultures (1.54 g L^− 1) supplemented with 1 g L^− 1 bicarbonate whereas there was no much difference in cellular lipid concentration (16 mg mL^− 1). GC–MS analysis of fatty acids showed highest amounts of palmitic acid, myristic and stearic acid. In summary, the addition of sodium bicarbonate increases cellular abundance, chlorophyll content and to some extent in the case of lipid content in C. vulgaris integrated with CO₂ sequestration.