Influence of Nitrate Feeding on Carbon Dioxide Fixation by Microalgae

Abstract

In this study, the effects of nitrate feeding on microalgal growth and associated CO2 fixation were evaluated, as a strategy to enhance carbon fixation by increasing the duration of the exponential phase of cell growth in the batch operation of a photobioreactor. Two species of green algae, Chlorella and Scenedesmus, and two species of cyanobacteria, Microcystis ichthyoblabe and Microcystis aeruginosa, were used after adaptation to a 15% (v/v) CO2 environment. In the absence of nitrate feeding, nitrate concentrations declined rapidly and soon became a limiting factor. Nitrate feeding, administered in fed-batch mode to maintain 15-20 ppm of NO3-N, allowed for an extension of the exponential growth phase by more than 3 days, as well as a higher cell density, which subsequently resulted in an increase in photoautotrophic carbon fixation. The increases in the carbon fixation rate were in the ranges of 56.1-56.6% for the green algae, and between 68.2-68.8% for the cyanobacteria. The results indicated that intermittent nitrate feeding was a viable strategy for the augmentation of fixation productivity, and may thus be effectively applied as a substitute for conventional medium change, which has traditionally been employed in order to prolong the active growth duration.

Optimization of CO2 fixation by Chlorella kessleri cultivated in a closed raceway photo-bioreactor

“…It can be seen that the intermittent phosphate feeding increases the microalgal growth. This is in agreement with Jin et al (2006), who reported that intermittent nitrate feeding increases microalgal growth and can be used to prolong the duration of the exponential growth phase in a given photobioreactor system. The results also indicate that the model can capture the dynamics of dissolved CO 2 perfectly in short time intervals.…”

Cultivation of microalgae species in tertiary municipal wastewater supplemented with CO2 for nutrient removal and biomass production

“…and Nannochloropsis sp. has been reported the relatively high microalgal growth rates using 10-15% flue or synthetic CO 2 (Lee et al, 2002;Jin et al, 2006;Jiang et al, 2011).…”

CO2 Biomitigation and Biofuel Production Using Microalgae: Photobioreactors Developments and Future Directions

“…Fast-growing microalgal species prefer ammonium rather than nitrate as a primary nitrogen source (Green & Durnford, 1996); intermittent nitrate feeding, however, will enhance microalgal growth if a medium that lacks nitrate is used (Jin et al 2006). Under partial nitrogen deprivation, microalgae grow at lower rates, but produce significantly more lipids, which are reserve compounds synthesized under stress conditions, even at the expense of lower productivities (Lardon et al 2009).…”