title: Genetic manipulation of butyrate formation pathways in Clostridium butyricum.
abstract: Clostridium butyricum is one of the commonly used species for fermentative hydrogen production. While producing H₂, it can produce acids (lactic, acetic and butyric acids) and CO₂, as well as a small amount of ethanol. It has been proposed that elimination of competing pathways, such as the butyrate formation pathway, should increase H₂ yields in Clostridium species. However, the application of this strategy has been hindered by the unavailability of genetic tools for these organisms. In this study, we successfully transferred a plasmid (pMTL007) to C. butyricum by inter-specific conjugation with Escherichia coli and disrupted hbd, the gene encoding β-hydroxybutyryl-CoA dehydrogenase in C. butyricum. Fermentation data showed that inactivation of hbd in C. butyricum eliminated the butyrate formation pathway, resulting in a significant increase in ethanol production and an obvious decrease in H₂ yield compared with the wild type strain. However, under low partial pressure of H₂, the hbd-deficient strain showed increased H₂ production with the simultaneous decrease of ethanol production, indicating that H₂ production by C. butyricum may compete for NADH with the ethanol formation pathway. Together with the discovery of a potential bifurcating hydrogenase, this study extends our understanding of the mechanism of H₂ production by C. butyricum.
authors.affiliation: School of Earth and Environmental Sciences, The University of Adelaide, Adelaide, SA 5005, Australia.
authors.forename: Guiqin
authors.initials: G
authors.lastname: Cai
authors.forename: Bo
authors.initials: B
authors.lastname: Jin
authors.forename: Christopher
authors.initials: C
authors.lastname: Saint
authors.forename: Paul
authors.initials: P
authors.lastname: Monis
mesh_terms: D015094:3-Hydroxyacyl CoA Dehydrogenases / Q000235:genetics* / Q000378:metabolism*; D002087:Butyrates / Q000378:metabolism*; D046972:Clostridium butyricum / Q000201:enzymology / Q000235:genetics* / Q000378:metabolism*; D003227:Conjugation, Genetic; D004926:Escherichia coli / Q000235:genetics; D000431:Ethanol / Q000378:metabolism; D005285:Fermentation; D055786:Gene Knockout Techniques / Q000379:methods; D005818:Genetic Engineering; D006859:Hydrogen / Q000378:metabolism; D006864:Hydrogenase / Q000235:genetics / Q000378:metabolism; D053858:Metabolic Networks and Pathways; D009584:Nitrogen / Q000378:metabolism; D010313:Partial Pressure; D010957:Plasmids / Q000235:genetics
chemical_list: D002087:Butyrates; D000431:Ethanol; D006859:Hydrogen; D015094:3-Hydroxyacyl CoA Dehydrogenases; C021388:3-hydroxybutyryl-CoA dehydrogenase; D006864:Hydrogenase; D009584:Nitrogen