Enhanced growth and hydrocarbon production of Botryococcus braunii KMITL 2 by optimum carbon dioxide concentration and concentration-dependent effects on its biochemical composition and biodiesel properties

The purposes of this study were to find the optimum level of supplementing CO2 for increasing the biomass and hydrocarbon production of B. braunii KMITL 2 (A race) and to determine the effects of CO2 level on CO2 fixation and biodiesel properties. The experimental results showed that the alga supplemented with 10% CO2 produced the highest biomass (1.48 ± 0.02 g L−1) and CO2 fixation rate (100.43 ± 1.42 mg L−1 d−1) that were 2.7 and 5.3 times higher than the control (0.04% CO2). The gravimetric hydrocarbon content (36.82 ± 3.39%) and hydrocarbon titer (0.35 ± 0.03 g L−1) of the alga supplemented with 5% CO2 were 1.6 and 2.7 times higher than the control. Cultivation of this strain under 5% CO2 gave the highest hydrocarbon yield and good biodiesel properties with the lowest iodine value and a higher CN value than the ASTM D6751 and EN 14214 fuel standards.