초록
<B>Abstract</B><B>Background</B><P>As a renewable and clean energy carrier, the production of biohydrogen from low-value feedstock such as lignocellulose has increasingly garnered interest. The NADH-dependent reduced ferredoxin:NADP<SUP>+</SUP> oxidoreductase (NfnAB) complex catalyzes electron transfer between reduced ferredoxin and NAD(P)<SUP>+</SUP>, which is critical for production of NAD(P)H-dependent products such as hydrogen and ethanol. In this study, the effects on end-product formation of deletion of <I>nfnAB</I> from <I>Thermoanaerobacterium aotearoense</I> SCUT27 were investigated.</P><B>Results</B><P>Compared with the parental strain, the NADH/NAD<SUP>+</SUP> ratio in the <I>∆nfnAB</I> mutant was increased. The concentration of hydrogen and ethanol produced increased by (41.1 ± 2.37)% (<I>p</I> < 0.01) and (13.24 ± 1.12)% (<I>p</I> < 0.01), respectively, while the lactic acid concentration decreased by (11.88 ± 0.96)% (<I>p</I> < 0.01) when the <I>∆nfnAB</I> mutant used glucose as sole carbon source. No obvious inhibition effect was observed for either SCUT27 or SCUT27/<I>∆nfnAB</I> when six types of lignocellulose hydrolysate pretreated with dilute acid were used for hydrogen production. Notably, the SCUT27/<I>∆nfnAB</I> mutant produced 190.63-209.31 mmol/L hydrogen, with a yield of 1.66-1.77 mol/mol and productivity of 12.71-13.95 mmol/L h from nonsterilized rice straw and corn cob hydrolysates pretreated with dilute acid.</P><B>Conclusions</B><P>The <I>T. aotearoense</I> SCUT27/<I>∆nfnAB</I> mutant showed higher hydrogen yield and productivity compared with those of the parental strain. Hence, we demonstrate that deletion of <I>nfnAB</I> from <I>T. aotearoense</I> SCUT27 is an effective approach to improve hydrogen production by redirecting the electron flux, and SCUT27/<I>∆nfnAB</I> is a promising candidate strain for efficient biohydrogen production from lignocellulosic hydrolysates.</P>