Simultaneous enhancement of microalgae biomass growth and lipid accumulation under continuous aeration with 15% CO2

To overcome the opposing trends in biomass yield and lipid accumulation, Chlorella PY-ZU1 cultures were continuously aerated with 15% CO2 to simultaneously enhance biomass yield (2.78 g L-1) and lipid content (47.04%). Microalgal cells consumed almost all the nitrate in the culture after 1 day to synthesize 24 mg L-1 of chlorophyll, which supported a peak growth rate of 0.675 g L-1 per day. Meanwhile, increased expression of key enzymes related to lipid synthesis (e.g., acetyl coenzyme A) enhanced lipid productivity to 192.10 mg L-1 per day. During the growth process, the carbon content of the dried biomass increased from 47.00% to 56.02% while the nitrogen content decreased from 6.36% to 1.99%. The unsaturated fatty acids decreased and saturated fatty acids increased, thus improving the anti-oxidation stability of microalgal biodiesel.