Simultaneous carbon dioxide sequestration and nitrate removal by Chlorella vulgaris and Pseudomonas sp. consortium

Carbon dioxide and nitrogen oxides are the main components of fossil flue gas causing the most serious environmental problems. Developing a sustainable and green method to treat carbon dioxide and nitrogen oxides of flue gas is still challenging. Here, a co-cultured microalgae/bacteria system, Chlorella vulgaris and Pseudomonas sp., was developed for simultaneous sequestration of CO₂ and removal of nitrogen oxides from flue gas, as well as producing valuable microalgae biomass. The co-cultured Chlorella vulgaris and Pseudomonas sp. showed the highest CO₂ fixation and NO₃^--N removal rate of 0.482 g L^-1d^-1 and 129.6 mg L^-1d^-1, the total chlorophyll accumulation rate of 65.6 mg L^-1 at the initial volume ratio of Chlorella vulgaris and Pseudomonas sp. as 1:10. The NO₃^--N removal rate can be increased to 183.5 mg L^-1d^-1 by continuous addition of 0.6 g L^-1d^-1 of glucose, which was 37% higher than that of co-culture system without the addition of glucose. Photosynthetic activity and carbonic anhydrase activity of Chlorella vulgaris were significantly increased when co-cultured with Pseudomonas sp. Excitation-emission matrix (EEM) fluorescence spectroscopy indicated that the humic acid-like substances released from Pseudomonas sp. could increase the growth of microalgae. This work provides an attractive way to simultaneously treatment of CO₂ and NO_X from flue gas to produce valuable microalgal biomass.