Production of biodiesel by autotrophic Chlorella pyrenoidosa in a sintered disc lab scale bubble column photobioreactor under natural sunlight

Abstract

The main focus of the work is to study Chlorella pyrenoidosa mediated photoautotrophic production of lipid in a bubble column photobioreactor using CO₂ as carbon source under natural diurnal outdoor sunlight. The limiting and inhibiting concentrations of CO₂ in sparging gas, nitrogen inhibition, reversibility of the CO₂ inhibition on growth, and lipid production have been investigated under natural sunlight. A process model coupled with light distribution inside the culture has been developed considering different concentration of dissolved CO₂ and urea, repression of nitrogen on lipid production under natural sunlight diurnal in nature in a bubble column reactor. The biomass titer of 4.6 g/L with 10% CO₂ has been achieved within 5 days of culture under sunlight. A two stage photoautotrophic lipid production strategy in a sintered disc bubble column photobioreactor under natural sunlight has been developed. 30% (w/w-DCW) lipid within 5 days of lipid induction period has been achieved. The biomass productivity of 0.91 ± 0.01 gm/L/day in growth period with sufficient urea and lipid productivity of 410 ± 12 mg/L/day in last 2 days of urea starvation period have been achieved in outdoor photoautotrophic cultivation under natural sunlight using CO₂ as carbon source.

Keywords:

• Bubble column
• diurnal sunlight
• lipid
• microalgae
• photoautotrophic

Acknowledgments

Authors would like to thanks to IIT Guwahati for supporting the fund for this research. Also authors would like to thanks to NCL Pune for giving the microalgae strain.

Additional information

Funding

The authors wish to thank Indian Institute of Technology Guwahati for funding.