초록
<P><B>Abstract</B></P> <P>Ferredoxin I (FdI), encoded by <I>fdxN</I> gene, is proved to be the main electron donor of nitrogenase for hydrogen production. In this work, <I>fdxN</I> gene overexpression was implemented in a mutant MHY01, which was constructed by inserting <I>fdxN</I> gene into the <I>hupSL</I> region in <I>Rhodobacter sphaeroides</I> HY01 genome. Its photo-fermentative H<SUB>2</SUB> production performance was studied. The results showed that the expression level of <I>fdxN</I> and nitrogenase activity in MHY01 (<I>hupSL</I>::<I>fdxN</I>) were enhanced by 177% and 61.7% respectively compared with that of wild type HY01. Using 25 mM acetate and 34 mM butyrate as carbon source and 6 mM <SMALL>L</SMALL>-glutamate as nitrogen source, the maximum H<SUB>2</SUB> production rate was 156.1 mL/(L·h), which was increased by 50.7% compared with that of HY01. The maximum H<SUB>2</SUB> production rates of MHY01 were enhanced by 30.0%, 52.5% and 50.7% compared with those obtained from HY01 at the inoculation size of 5%, 10% and 15% respectively. The results suggested that overexpressing <I>fdxN</I> could enhance the nitrogenase activity and H<SUB>2</SUB> production performance of purple non-sulfur bacteria. The abundancy of ferredoxin I might limit the efficiency of electron transfer flux associated with the biohydrogen production process.</P> <P><B>Highlights</B></P> <P> <UL> <LI> FdI content limits the efficiency of electron transport chain for H<SUB>2</SUB> production. </LI> <LI> Overexpressing <I>fdxN</I> gene could enhance the photofermentative H<SUB>2</SUB> production rate. </LI> <LI> Substitution of <I>hupSL</I> with <I>fdxN</I> was implemented in <I>R. sphaeroides</I> genome. </LI> <LI> Deleting <I>hupSL</I> and overexpressing <I>fdxN</I> showed synergistic effect on H<SUB>2</SUB> production. </LI> <LI> The inoculum size affected the <I>fdxN</I> overexpression strains more significantly. </LI> </UL> </P>