Effects of Nitrogen Availability on the Bioenergy Production Potential and CO2 Fixation of Thermosynechococcus CL-1 under Continuous Cultivation

Received: November 30, 2012
Revised: March 21, 2013
Accepted: March 21, 2013
Download Citation: RIS|BibTeX|https://doi.org/10.4209/aaqr.2012.11.0333  

Cite this article:
Su, C.M., Hsueh, H.T., Chen, H.H. and Chu, H. (2013). Effects of Nitrogen Availability on the Bioenergy Production Potential and CO2 Fixation of Thermosynechococcus CL-1 under Continuous Cultivation. Aerosol Air Qual. Res. 13: 1321-1330. https://doi.org/10.4209/aaqr.2012.11.0333

ABSTRACT

Nitrogen availability directly affects the microalgal metabolism. A thermophilic cyanobacterium named Thermosynechococcus CL-1 was cultivated in a continuous system to evaluate the effects of NO₃^– fluxes on the biomass production, bioenergy production, and CO₂ fixation. The results show that decreasing the NO₃^– flux to a N-deprived level (1.01 mM/d) enhances the carbohydrate content in TCL-1 to 45%, accompanied by a decrease in the lipid content. However, increasing the NO₃^– flux from a N-deprived level (1.01 mM/d) decreases the carbohydrate content dramatically, accompanied by a slight increase in the lipid content. No matter whether the NO₃^– flux decreases from a N-replete level (8.35 mM/d) to a N-deprived one (1.01 mM/d), or increases from a N-deprived level to higher one, the peak biomass yield occurs at the same NO₃^– flux level, 4.18 mM/d. In addition, the peak lipid yield, carbohydrate yield, and CO₂ fixation rate were recorded at 482 and 660 mg/L/d, and 3.9 g/L/d, respectively, under the same NO₃^– flux level (4.18 mM/d). Although cultivating TCL-1 under the 4.18 mM/d NO₃^– flux level exhibits great biomass production, CO₂ fixation, and bioenergy production potential, different procedures (the NO₃^– flux decreasing from the N-replete level and the NO₃^– flux increasing from the N-deprived level) could influence the final quantity of bioenergy production and CO₂ fixation. The NO₃^– flux, NO₃^– concentration in the bioreactor, and the NO₃^– flux variation routes are all important factors to determine the nitrogen availability of TCL-1 in continuous cultivation.

Keywords: Nitrogen availability; Thermosynechococcus; Continuous operation; Bioenergy; CO2 fixation