Elimination of hydrogenase active site assembly blocks H2 production and increases ethanol yield in Clostridium thermocellum [electronic resource]

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Ngôn ngữ: eng

Ký hiệu phân loại: 668.5 Perfumes and cosmetics

Thông tin xuất bản: Washington, D.C. : Oak Ridge, Tenn. : United States. Dept. of Energy. Office of Science ; Distributed by the Office of Scientific and Technical Information, U.S. Dept. of Energy, 2015

Mô tả vật lý: Size: Article No. 20 : , digital, PDF file.

Bộ sưu tập: Metadata

ID: 263706

 Background: The native ability of <
 i>
 Clostridium thermocellum<
 /i>
  to rapidly consume cellulose and produce ethanol makes it a leading candidate for a consolidated bioprocessing (CBP) biofuel production strategy. <
 i>
 C. thermocellum<
 /i>
  also synthesizes lactate, formate, acetate, H-2, and amino acids that compete with ethanol production for carbon and electrons. Elimination of H-2 production could redirect carbon flux towards ethanol production by making more electrons available for acetyl coenzyme A reduction to ethanol. Results: H-2 production in <
 i>
 C. thermocellum<
 /i>
  is encoded by four hydrogenases. Rather than delete each individually, we targeted hydrogenase maturase gene <
 i>
 hydG<
 /i>
 , involved in converting the three [FeFe] hydrogenase apoenzymes into holoenzymes. Further deletion of the [NiFe] hydrogenase (<
 i>
 ech<
 /i>
 ) resulted in a mutant that functionally lacks all four hydrogenases. H-2 production in ?hydG?ech was undetectable, and the ethanol yield nearly doubled to 64% of the maximum theoretical yield. Genomic analysis of ?hydG revealed a mutation in <
 i>
 adhE<
 /i>
 , resulting in a strain with both NADH- and NADPH-dependent alcohol dehydrogenase activities. While this same <
 i>
 adhE<
 /i>
  mutation was found in ethanol-tolerant <
 i>
 C. thermocellum<
 /i>
  strain E50C, ?hydG and ?hydG?ech are not more ethanol tolerant than the wild type, illustrating the complicated interactions between redox balancing and ethanol tolerance in <
 i>
 C. thermocellum<
 /i>
 . Conclusions: Finally, the dramatic increase in ethanol production suggests that targeting protein post-translational modification is a promising new approach for simultaneous inactivation of multiple enzymes.
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