Clotridial hydrogenases and the biohydrogen production

Poster (2010, July 01)

Among the large variety of microorganisms capable of fermentative hydrogen production, strict anaerobes such as Clostridium spp. are one of the most widely studied. They produce hydrogen by butyric and ... [more ▼]

Among the large variety of microorganisms capable of fermentative hydrogen production, strict anaerobes such as Clostridium spp. are one of the most widely studied. They produce hydrogen by butyric and mixed-acid fermentations at optimal pH values ranging from 4.5 to 5.5. While fermentative conditions such as substrate type, pH, hydraulic and solid retention time, H2 partial pressure and the concentration of acids produced have been extensively studied and optimized, relatively little is known about the different forms of hydrogenases present in clostridia. Building on previous reports [1, 2] and by analyzing sequenced genomes, we found that [FeFe] hydrogenases are not a homogenous group of enzymes, but exist in multiple forms with different modular structures and are especially abundant in Clostridum spp. [3]. However, among the numerous studies performed on fermentative hydrogen production by Clostridium sp., only a few are specifically concerned with hydrogenases. Even there the authors focus on one type of [FeFe] hydrogenase, (CpI-like) without considering the existence of multiple forms of this enzyme within one species. Therefore, we focused our research on the better characterization of different forms of hydrogenases present in the genus Clostridium. Using newly designed degenerate primers, specific for clostridial hydrogenases, we amplified different hydrogenases from our species of interest. Further, by designing specific qPCR assays we have quantitatively targeted different hydrogenases. By analyzing differential gene expression, according to applied growth conditions, we believe to optimize the hydrogen production process in order to achieve better production rates. To conclude, we think that a a precise knowledge of hydrogen metabolism and hydrogenases is essential to optimization of the biohydrogen production process and should therefore be a goal for future research. [less ▲]

The surprising diversity of clostridial hydrogenases: a comparative genomic perspective

in Microbiology (2010), 156

Among the large variety of micro-organisms capable of fermentative hydrogen production, strict anaerobes such as members of the genus Clostridium are the most widely studied. They can produce hydrogen by ... [more ▼]

Among the large variety of micro-organisms capable of fermentative hydrogen production, strict anaerobes such as members of the genus Clostridium are the most widely studied. They can produce hydrogen by a reversible reduction of protons accumulated during fermentation to dihydrogen, a reaction which is catalysed by hydrogenases. Sequenced genomes provide completely new insights into the diversity of clostridial hydrogenases. Building on previous reports, we found that [FeFe] hydrogenases are not a homogeneous group of enzymes, but exist in multiple forms with different modular structures and are especially abundant in members of the genus Clostridium. This unusual diversity seems to support the central role of hydrogenases in cell metabolism. In particular, the presence of multiple putative operons encoding multisubunit [FeFe] hydrogenases highlights the fact that hydrogen metabolism is very complex in this genus. In contrast with [FeFe] hydrogenases, their [NiFe] hydrogenase counterparts, widely represented in other bacteria and archaea, are found in only a few clostridial species. Surprisingly, a heteromultimeric Ech hydrogenase, known to be an energy-converting [NiFe] hydrogenase and previously described only in methanogenic archaea and some sulfur-reducing bacteria, was found to be encoded by the genomes of four cellulolytic strains: Clostridum cellulolyticum, Clostridum papyrosolvens, Clostridum thermocellum and Clostridum phytofermentans [less ▲]