Carbon speciation and flocculation in Neochloris oleoabundans cultures using anaerobically digested stillage
- 109 Downloads
The effects of bicarbonate loading rate (BLR) and pH on growth kinetics, inorganic carbon speciation, carbon fixation and lipid content in Neochloris oleoabundans cultures using anaerobically digested stillage (ADS) (2% v/v) were investigated. Four different cultures were established: culture A with BLR = 1 g l−1 day−1 and no pH adjustment, culture B with BLR = 0.5 g l−1 day−1 and no pH adjustment, culture C with BLR = 1 g l−1 day−1 and pH adjustment at 7.0, and culture D with BLR = 0.5 g l−1 day−1 and pH adjustment at 7.0. The experiments were carried out in flat plate reactors (4 l) at controlled conditions (light intensity of 134 µmol photon m−1 s−1 and photoperiod 16 light/8 darkness; temperature of 32 ± 1 °C). The effects of pH (7, 10.41, 10.65, and 12), time (15, 30, 60, and 90 min), and concentration of a cationic polyelectrolyte (CP) (10 and 20 mg l−1) on the flocculation efficiency (FE) of N. oleoabundans were also investigated. The results showed that bicarbonate was the predominant carbon species in the media and the main carbon source for microalgae growth in all cultures. The highest productivity (87.70 ± 9.70 mg l−1 day−1) and CO2(aq) fixation rate (0.15 g CO2(aq) l−1 day−1) were found in culture B. The lipid content in N. oleoabundans was affected negatively by the pH adjustment at 7.0 during its growth; higher values were found in cultures with no pH adjustment (37.10% and 38.85% dw for culture A and B, respectively) as compared to those obtained in cultures with pH adjustment (27.35% and 22.20% dw for culture C and D, respectively) (p < 0.05). Regarding flocculation, the addition of 20 mg CP l−1 was required to obtain a FE > 95% in cultures A and B, although a significant FE (40–59%) occurred without CP addition at a high pH (≥ 10.41) in all cultures.
KeywordsMicroalgae Anaerobic effluent Carbon fixation Lipids Flocculation
The authors thank the technical assistance of Anilú Mendoza, Karla Tapia, Alejandro Hernández and Victor Hernández-Landa.
This study was funded by the Ministry of Energy (SENER) and the National Research Council of México (CONACYT) (Project #152931).
Compliance with ethical standards
Conflict of interest
The authors declare that they have no conflict of interest.
- Beach ES, Eckelman MJ, Cui Z et al (2012) Preferential technological and life cycle environmental performance of chitosan flocculation for harvesting of the green algae Neochloris oleoabundans. Bioresour Technol 121:445–449. https://doi.org/10.1016/j.biortech.2012.06.012 CrossRefPubMedGoogle Scholar
- Giordano M, Beardall J, Raven JA (2005) CO2 concentrating mechanisms in algae: mechanisms, environmental modulation, and evolution. Ann Rev Plant Biol 56:99–131. https://doi.org/10.1146/annurev.arplant.56.032604.144052 CrossRefGoogle Scholar
- González-Fernández C, Molinuevo-Salces B, García-González MC (2011) Nitrogen transformations under different conditions in open ponds by means of microalgae–bacteria consortium treating pig slurry. Bioresour Technol 102(2):960–966. https://doi.org/10.1016/j.biortech.2010.09.052 CrossRefPubMedGoogle Scholar
- Lecina M, Nadal G, Solà C et al (2016) Optimization of ferric chloride concentration and pH to improve both cell growth and flocculation in Chlorella vulgaris cultures. Application to medium reuse in an integrated continuous culture bioprocess. Bioresour Technol 216:211–218. https://doi.org/10.1016/j.biortech.2016.05.063 CrossRefPubMedGoogle Scholar
- Roselet F, Vandamme D, Roselet M et al (2015) Screening of commercial natural and synthetic cationic polymers for flocculation of freshwater and marine microalgae and effects of molecular weight and charge density. Algal Res 10:183–188. https://doi.org/10.1016/j.algal.2015.05.008 CrossRefGoogle Scholar