Performance and mechanism of carbon dioxide fixation by a newly isolated chemoautotrophic strain Paracoccus denitrificans PJ-1

CO 2 is regarded as a major contributor to the global warming. CO 2 utilization is promising to reduce the CO 2 emissions. Currently, the biofixation of CO 2 using chemoautotrophs has markedly gain interest in CO 2 utilization. In this study, a newly isolated chemoautotroph, Paracoccus denitrificans PJ-1, was used for the biofixation of CO 2 under anaerobic condition . Experimental results revealed that Paracoccus denitrificans PJ-1 achieved a high carbon fixation rate (13.25 mg·L −1 ·h −1 ) which was ∼10 times faster than the previous reported chemotrophic bacteria using thiosulfate as electron donor. The best CO 2 fixation activity of Paracoccus denitrificans PJ-1 was achieved at the pH value of 9.0 and CO 2 concentration of 20 vol%. Meanwhile, a high CO 2 fixation yield of 106.03 mg·L −1 was reached. The presence of oxygen was adverse to the biofixation, indicating that strain PJ-1 was more suitable for CO 2 fixation in anaerobic environments. Carbon mass balance analysis revealed that the carbon from CO 2 was mainly fixed into the extracellular organic carbon rather than the biomass. GC-MS analysis and cbbL gene test revealed that Paracoccus denitrificans PJ-1 fixed CO 2 through the Calvin-Benson-Bassham cycle and mainly converted CO 2 to oxalic acid and succinic acid. Overall, the excellent CO 2 fixation capacity of Paracoccus denitrificans PJ-1 suggests that it had potential for CO 2 utilization.