초록
In this study, fresh water methane-producing bacterium (MPB), strain FJ10, which used H<SUB>2</SUB> as an electron donor and CO<SUB>2</SUB> as an electron acceptor, was isolated and chosen as the primary methanogen for the conversion of CO<SUB>2</SUB> into CH<SUB>4</SUB>. Improvements to culture medium to increase methane production were investigated using a fractional factorial design in 32 experiments with six variables under consumption of H<SUB>2</SUB>/CO<SUB>2</SUB> at ratios of 4 and 1. The tested nutrient compositions were NaCl, NH<SUB>4</SUB>Cl, FeSO<SUB>4</SUB>, MgCl<SUB>2</SUB>, H<SUB>2</SUB>PO<SUB>4</SUB> and yeast extract. Experimental results indicate that yeast extract was essential for the growth of strain FJ10 to impact the conversion of CO<SUB>2</SUB> into CH<SUB>4</SUB>. Strain FJ10 generated maximum CH<SUB>4</SUB> production with 5.0g/l of yeast extract. Moreover, optimal culture conditions for methane production by strain FJ10 were 40<SUP>o</SUP>C and pH 8. Approximately 22-25% of CO<SUB>2</SUB> conversion into CH<SUB>4</SUB> was achieved at an H<SUB>2</SUB>/CO<SUB>2</SUB> ratio of 4 and roughly 2.5-6% of CO<SUB>2</SUB> conversion into CH<SUB>4</SUB> was obtained at an H<SUB>2</SUB>/CO<SUB>2</SUB> ratio of 1 under different pressurized conditions of 1atm, 50atm and 100atm. Under 100atm, about 6780μM CH<SUB>4</SUB> was produced with an H<SUB>2</SUB>/CO<SUB>2</SUB> ratio of 4 and 4240μM CH<SUB>4</SUB> was produced with an H<SUB>2</SUB>/CO<SUB>2</SUB> ratio of 1 under the steady state condition. The kinetic model for H<SUB>2</SUB>/CO<SUB>2</SUB> utilization and CH<SUB>4</SUB> production under different pressures was verified by experimental data. Model predictions are in good agreement with experimental results. The experimental and modeling approaches in this study can be applied to evaluate the conversion of CO<SUB>2</SUB> into CH<SUB>4</SUB> as an energy source by geo-microorganisms in geological sequestration.