Optimization of photoautotrophic lipid production of Chlorella ellipsoidea seeded with heterotrophic cells

Abstract:

Photoautotrophic cultivation with heterotrophic cells as seeds (heterotrophic cells / photoautotrophic cultivation) is an effective way for the development of microalgal biofuel, but its development potential from the point of process optimization has not been investigated in literatures. To evaluate this, the optimizations of medium and culture conditions for Chlorella ellipsoidea were studied. In the heterotrophic stage, the biomass concentration reached 11.04 g/L with the optimized medium in flask, which were 28.0% higher than that with the original medium, and the biomass concentration reached 73.89 g/L in 5-L fermenter. In the photoautotrophic stage, the culture medium and conditions were studied in a 2-L column photobioreactor. The maximum biomass concentration, lipid content and lipid productivity reached 1.62 g/L, 36.34% and 6.1 mg/(L·h) under the optimal photoautotrophic conditions. The lipids were mainly composed of C16-C18 fatty acids, which were raw material suitable for biodiesel. After optimization, heterotrophic cells / photoautotrophic cultivation can significantly improve the capacity of biofuel production by Chlorella ellipsoidea, this method is also expected to be an efficient way for the cultivation of other microalgae that can grow heterotrophically.