School of Earth and Environmental Sciences, The University of Adelaide, Adelaide, SA 5005, Australia.
J Biotechnol. 2011 Sep 20;155(3):269-74. doi: 10.1016/j.jbiotec.2011.07.004. Epub 2011 Jul 19.
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.
丁酸梭菌是发酵产氢常用的物种之一。在产氢的同时，它可以产生酸（乳酸、乙酸和丁酸）和 CO₂，以及少量的乙醇。有人提出，消除竞争途径，如丁酸盐形成途径，应该可以提高梭菌属物种的氢气产量。然而，由于这些生物体缺乏遗传工具，该策略的应用受到了阻碍。在这项研究中，我们通过大肠杆菌的种间共轭成功地将质粒（pMTL007）转移到丁酸梭菌中，并敲除了丁酸梭菌中编码β-羟丁酰辅酶 A 脱氢酶的 hbd 基因。发酵数据表明，丁酸梭菌中 hbd 的失活消除了丁酸盐形成途径，导致乙醇产量显著增加，与野生型菌株相比，氢气产量明显下降。然而，在低氢气分压下，hbd 缺陷型菌株的氢气产量增加伴随着乙醇产量的降低，表明丁酸梭菌的氢气生产可能与乙醇形成途径竞争 NADH。结合发现一种潜在的分支氢化酶，本研究扩展了我们对丁酸梭菌产氢机制的理解。
