A novel photobioreactor was developed with a total volume of 30 m(3) which required merely 100 m(3) of land footprint. The bioreactor was capable of utilizing CO2 in the flue gas of a power plant as the carbon source for the growth of a freshwater alga, Spirulina platensis, mitigating the greenhouse effect caused by the same amount of CO2 discharge. Results of the study indicated that the photobioreactor was capable of fixing 2,234 kg of CO2 per annum. Upon deducting the energy consumption of operating the bioreactor unit, the estimated amount of CO2 to be fixed by a scaled-up reactor would be 74 tons ha(-1) year(-1). In addition, the study proved that protein-free polysaccharides of S. platensis could induce the production of pro-IL- and IL-1 proteins through the mediation of ERK, JNK, and p38 MAPKs pathways. As a consequence, immunogenic activities of the macrophage cells were enhanced. (C) 2012 Elsevier Ltd. All rights reserved.