Enhanced CO2 fixation by a non-photosynthetic microbial community under anaerobic conditions: Optimization of electron donors

To enhance the CO2 fixation efficiency of the non-photosynthetic microbial community (NPMC) isolated from sea water under anaerobic conditions without hydrogen, the concentration of inorganic compounds as electron donors and their ratios were optimized by response surface methodology design (RSMD). The results indicated that the CO2 fixation efficiency of NPMC using NaNO2, Na2S2O3 and Na2S as the electron donors was increased about 90%, 75% and 207%, respectively. Additionally, there were interactions between two electron donors and three electron donors. Central composite RSMD experimentation predicted that the optimal concentration and ratios of these inorganic compounds was 1.04% NaNO2, 1.07% Na2S2O3 and 0.98% Na2S. Under these conditions, the fixed CO2 was 139.89 mg/L, which obviously exceeded the amount prior to optimization, as well as when H2 was used as an electron donor. The established electron donor system can effectively enhance the CO2 fixation efficiency of NPMC without hydrogen under anaerobic conditions.