초록
<P><B>Abstract</B></P> <P>The electro-biocatalytic conversion of CO<SUB>2</SUB> into formic acid using whole-cell and isolated biocatalysts is useful as an alternative route for CO<SUB>2</SUB> sequestration. In this study, <I>Shewanella oneidensis</I> MR-1 (<I>S. oneidensis</I> MR-1), a facultative aerobic bacterium that has been extensively studied for its utility as biofuel cells as well as for the detoxification of heavy metal oxides (i.e., MnO<SUB>2</SUB>, uranium), has been applied for the first time as a whole-cell biocatalyst for formic acid synthesis from gaseous CO<SUB>2</SUB> and electrons supplied from an electrode. <I>S. oneidensis</I> MR-1, when aerobically grown in Luria-Bertani (LB) medium, exhibited its ability as a whole-cell biocatalyst for the conversion of CO<SUB>2</SUB> into formic acid with moderate productivity of 0.59 mM h<SUP>−1</SUP> for 24 h. In addition, an optimization of growth conditions of <I>S. oneidensis</I> MR-1 resulted in a remarkable increase in productivity. The CO<SUB>2</SUB> reduction reaction catalyzed by <I>S. oneidensis</I> MR-1, when anaerobically grown in newly optimized LB medium supplemented with fumarate and nitrate, exhibited 3.2-fold higher productivity (1.9 mM h<SUP>−1</SUP> for 72 h) compared to that grown aerobically in only LB medium. Furthermore, the average conversion rate of formic acid synthesis catalyzed by <I>S. oneidensis</I> MR-1 when grown in the optimal medium over a period of 72 h was 3.8 mM h<SUP>−1</SUP> g<SUP>−1</SUP> wet-cell, which is 9.6-fold higher than that catalyzed by <I>Methylobacterium extorquens</I> AM1 whole-cells in our previous study.</P> <P><B>Highlights</B></P> <P> <UL> <LI> <I>Shewanella oneidensis</I> MR-1 microbial has shown capability to reduce CO<SUB>2</SUB> to formate by using electrons supplied from cathode. </LI> <LI> Anaerobically grown microbial in newly optimized LB medium supplemented with fumarate and nitrate exhibited 3.2-fold higher productivity. </LI> <LI> Maximum formate concentration produced by whole cell approached about 150 mM in 72 h. </LI> </UL> </P>