Elimination of H₂ production in Clostridium thermocellum Increases its Ethanol Yield

The ability of Clostridium thermocellum to consume cellulose and produce ethanol makes it a leading candidate for a consolidated bioprocessing (CBP) biofuel production. However, it also produces substances, such as H₂, that compete with ethanol production for carbon and electrons. Elimination of H₂ production could redirect carbon towards ethanol production.

H₂ production in C. thermocellum is encoded by four hydrogenases. Adam M. Guss of the Oak Ridge National Laboratory, and his team, targeted the hydG gene, involved in converting the [FeFe] hydrogenase apoenzymes into holoenzymes. Further deletion of the ech gene resulted in a mutant that functionally lacks all four hydrogenases. H₂ production in the resulting transgenics without both hydG and ech was undetectable, and the ethanol yield nearly doubled.

The significant increase in ethanol production suggests that targeting protein post-translational modification is a promising new technique for simultaneous inactivation of multiple enzymes.