Sugar-stimulated CO2 sequestration by the green microalga Chlorella vulgaris

• Published in: The Science of the total environment 2019-03, Vol.654, p.275-283
• Main Authors: Fu, Weiqi, Gudmundsson, Steinn, Wichuk, Kristine, Palsson, Sirus, Palsson, Bernhard O., Salehi-Ashtiani, Kourosh, Brynjólfsson, Sigurður
• Format: Article
• Language: English
• Subjects: Chlorella vulgaris; CO2 capture; Fine-tuned mixotrophic growth; LED illumination; Microalga
• ISSN: 0048-9697; 1879-1026
• DOI: 10.1016/j.scitotenv.2018.11.120

To convert waste CO2 from flue gases of power plants into value-added products, bio-mitigation technologies show promise. In this study, we cultivated a fast-growing species of green microalgae, Chlorella vulgaris, in different sizes of photobioreactors (PBRs) and developed a strategy using small doses of sugars for enhancing CO2 sequestration under light-emitting diode illumination. Glucose supplementation at low levels resulted in an increase of photoautotrophic growth-driven biomass generation as well as CO2 capture by 10% and its enhancement corresponded to an increase of supplied photon flux. The utilization of urea instead of nitrate as the sole nitrogen source increased photoautotrophic growth by 14%, but change of nitrogen source didn't compromise glucose-induced enhancement of photoautotrophic growth. The optimized biomass productivity achieved was 30.4% higher than the initial productivity of purely photoautotrophic culture. The major pigments in the obtained algal biomass were found comparable to its photoautotrophic counterpart and a high neutral lipids productivity of 516.6 mg/(L·day) was achieved after optimization. A techno-economic model was also developed, indicating that LED-based PBRs represent a feasible strategy for converting CO2 into value-added algal biomass. [Display omitted] •Fine-tuning mixotrophic culture of microalgae enhances CO2 bio-fixation.•CO2 capture in sugar-stimulated algal culture enhanced with increased light supply.•Sugar-stimulated algae have as much pigments as its photoautotrophic counterpart.•A techno-economic model evaluates the feasibility of large-scale algae cultivation.