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영어

The hupSLD-hypQ3Q4F gene cluster located in the pSOL1 megaplasmid of C. acetobutylicum ATCC 824 potentially encodes a [NiFe]-hydrogenase. The gene cluster is organized in an operon comprising six genes. The operon is expressed only in a solventogenic state, but neither in an alcohologenic nor acidogenic state.Generally, [NiFe]-hydrogenase are known as hydrogen consuming enzymes but little is known about the function of [NiFe]-hydrogenase in Clostridia. Thus, batch fermentation profiles were conducted with two different mutants with disruptions in the hupSLD-hypQ3Q4F operon and a control strain in MS medium without pH control.The product profiles of the hupL knockout mutant were found not to be significantly different from those of the control strain. In contrast, a deletion mutant of hypQ3Q4 produced more butanol, transiently accumulated less butyrate, and produced less hydrogen compared to the control strain. It seems that [NiFe]-hydrogenase in C. acetobutylicum is hydrogen producing enzyme, so accordingly the decrease of hydrogen from defective [NiFe]-hydrogenase during solventogenesis phase affected reducing equivalents of reduced ferredoxin and NAD(P)H.