| dc.description.abstract | Normally biogas contains ~40% CO2 and it may severely hinder the combustion efficiency of biogas and cause greenhouse effect accordingly. Microalgae have been known to be able to recycle/metabolize CO2 through photosynthesis and produce abundance of chemicals/biologicals in form of biomass and/or biolipids, showing a high potential for use in CO2 removal for biogas purification. However, the amount of CO2 given to microalgae has to be adequately controlled to avoid CO2-induced inhibitory effect on the microalgal growth. To meet this goal, a perfluorocarbon (PFC)-mediated photobioreactor setup, named perfluorinated photobioreactor system (PPBRS), was developed in this study. We first examined the effect of gas flow rate on the growth of Nannochloropsis oculata (N. oculata) by using normal air as the model gas. Then we investigated 1) how the concentration of CO2 in range of 1 – 6% affects the growth and productions of N. oculata, including biomass, total lipid, and eicosapentaenoic acid (EPA); and 2) capability of PPBRS for CO2 absorption from a mixture gas in sequence. Ultimately the effects of using PPBRS to absorb CO2 form a mixture gas and convert those isolated CO2 to enhanced growth and productions of N. oculata were comprehensively examined. Our data show that the microalgal growth enhanced along with increase of the flow rate of air that the concentration of cells provided by air with flow rate of 1000 mL/min remarkably enhanced 7 folds as compared to the group without air supply. Among different CO2 concentrations provided by FC-40 with flow rate of 20 mL/min, the group with 2% CO2 exhibits the highest productions of N. oculata that the concentration of microalgae, as well as their productions of biomass, total lipid, and EPA dramatically enhanced 2 folds after operation for 5 days, showing that 2% CO2 is the optimal setting for N. oculata growth in PPBRS. In addition, our results show that the capacity of FC-40-mediated purification unit for CO2 adsorption from a N2/CO2 mixture (N2 : CO2 = 3:2 v/v) is 2-fold higher than that obtained by using water within 12 h, implicating that PPBRS is capable for CO2 isolation. Through the operation with PPBRS, we found that the CO2 concentration remaining in the input N2/CO2 mixture (N2 : CO2 = 3:2 v/v) was < 5% (v/v) throughout the experiment and the concentration of N. oculata cultured with isolated CO2 significantly enhanced 2 folds as compared to the cells normally cultivated with air supply under equal delivery velocity (20 mL/min). In summary, we anticipate that the developed PPBRS may offer a feasible means to 1) isolate CO2 from biogas and 2) enhance microalgal growth and productions concurrently in a closed and large-scale setting. | en_US |