Optimization of electron donors to improve CO2 fixation efficiency by a non-photosynthetic microbial community under aerobic condition using statistical experimental design.

To improve the CO(2) fixation efficiency of non-photosynthetic microbial community (NPMC) isolated from sea water under aerobic conditions without hydrogen, the concentration of inorganic compounds as electron donors and their ratios were optimized using response surface methodology design (RSMD). These results indicated that Na(2)S, followed by Na(2)S(2)O(3) and NaNO(2) enhanced the CO(2) fixation by NPMC and the efficiency was increased about 100%, 200% and 200%, respectively. Some interaction between NaNO(2) and Na(2)S(2)O(3), as well as between Na(2)S(2)O(3) and Na(2)S was observed. Central composite RSMD experimentation predicted that the optimal concentration of these inorganic compounds and their ratios was 0.457% NaNO(2), 0.50% Na(2)S(2)O(3) and 1.25% Na(2)S. Under these conditions, the fixed CO(2) was 105.76 mg/L, which obviously exceeded the amount before optimization, as well as that obtained using hydrogen as the electron donor. This indicates that the NPMC using the established electron donors system can effectively fix CO(2) without light and hydrogen gas under aerobic condition.