Advanced aspects of acetogens.

Acetogens are a diverse group of anaerobic bacteria that are capable of carbon dioxide fixation and have for long fascinated scientists due to their unique metabolic prowess. Historically, acetogens have been recognized for their remarkable ability to grow and to produce acetate from different one-carbon sources, including carbon dioxide, carbon monoxide, formate, methanol, and methylated organic compounds. The key metabolic pathway in acetogens responsible for converting these one-carbon sources is ́the Wood-Ljungdahl pathway.

Lactate-mediated mixotrophic co-cultivation of Clostridium drakei and recombinant Acetobacterium woodii for autotrophic production of volatile fatty acids.

Background: Acetogens, a diverse group of anaerobic autotrophic bacteria, are promising whole-cell biocatalysts that fix CO during their growth. However, because of energetic constraints, acetogens exhibit slow growth and the product spectrum is often limited to acetate. Enabling acetogens to form more valuable products such as volatile fatty acids during autotrophic growth is imperative for cementing their place in the future carbon neutral industry.

Recombinant Production of Rhamnolipids in KT2440 on Cultures Grown Chemo-Autotrophically with Carbon Dioxide and Hydrogen.

The establishment of sustainable processes for the production of commodity chemicals is one of today's central challenges for biotechnological industries. The chemo-autotrophic fixation of CO and the subsequent production of acetate by acetogenic bacteria via anaerobic gas fermentation represents a promising platform for the ecologically sustainable production of high-value biocommodities via sequential fermentation processes. In this study, the applicability of acetate-containing cell-free spent medium of the gas-fermenting acetogenic bacterium WP1 as the feeder strain for growth and the recombinant production of PAO1 mono-rhamnolipids in the well-established nonpathogenic producer strain KT2440 were investigated.

Complete genome sequences of DSM 10507 isolated from human feces and DSM 935 isolated from mouse feces.

We report on the closed genome sequences of the acetogen S5a33 (DSM 10507) and of CLC-1 (DSM 935). The S5a33 genome harbors a chromosome (3,590,609 bp) and a plasmid (7,176 bp). The CLC-1 genome consists of a single chromosome (6,097,890 bp).

Refining and illuminating acetogenic Eubacterium strains for reclassification and metabolic engineering.

Background: The genus Eubacterium is quite diverse and includes several acetogenic strains capable of fermenting C1-substrates into valuable products. Especially, Eubacterium limosum and closely related strains attract attention not only for their capability to ferment C1 gases and liquids, but also due to their ability to produce butyrate. Apart from its well-elucidated metabolism, E.

Genome-based metabolic and phylogenomic analysis of three Terrisporobacter species.

Acetogenic bacteria are of high interest for biotechnological applications as industrial platform organisms, however, acetogenic strains from the genus Terrisporobacter have hitherto been neglected. To date, three published type strains of the genus Terrisporobacter are only covered by draft genome sequences, and the genes and pathway responsible for acetogenesis have not been analyzed. Here, we report complete genome sequences of the bacterial type strains Terrisporobacter petrolearius JCM 19845T, Terrisporobacter mayombei DSM 6539T and Terrisporobacter glycolicus DSM 1288T.

Lactate based caproate production with and process control of via lactate dependent electrolysis.

Syngas fermentation processes with acetogens represent a promising process for the reduction of CO emissions alongside bulk chemical production. However, to fully realize this potential the thermodynamic limits of acetogens need to be considered when designing a fermentation process. An adjustable supply of H as electron donor plays a key role in autotrophic product formation.

Novel synthetic co-culture of and using CO and in situ generated H for the production of caproic acid via lactic acid.

is known to produce mainly acetate from CO and H, but the production of higher value chemicals is desired for the bioeconomy. Using chain-elongating bacteria, synthetic co-cultures have the potential to produce longer-chained products such as caproic acid. In this study, we present first results for a successful autotrophic co-cultivation of mutants and a wild-type strain in a stirred-tank bioreactor for the production of caproic acid from CO and H via the intermediate lactic acid.

Reclassification of Hellinger 1944 and (ex McCoy and McClung 1935) Cato . 1988.

, and share a very high similarity based on multi-locus sequence analysis. In this study, their correct taxonomic status was determined using genomic and phenotypic investigations. Average nucleotide identity based on MUMmer alignment of the genomes and DNA-DNA hybridization resulted in values of 98.

Autotrophic lactate production from H + CO using recombinant and fluorescent FAST-tagged Acetobacterium woodii strains.

Lactate has various uses as industrial platform chemical, poly-lactic acid precursor or feedstock for anaerobic co-cultivations. The aim of this study was to construct and characterise Acetobacterium woodii strains capable of autotrophic lactate production. Therefore, the lctBCD genes, encoding the native Lct dehydrogenase complex, responsible for lactate consumption, were knocked out.

Engineering Acetobacterium woodii for the production of isopropanol and acetone from carbon dioxide and hydrogen.

The capability of four genetically modified Acetobacterium woodii strains for improved production of acetone from CO and hydrogen was tested. The acetone biosynthesis pathway was constructed by combining genes from Clostridium acetobutylicum and Clostridium aceticum. Expression of acetone production genes was demonstrated in all strains.

Production of the biocommodities butanol and acetone from methanol with fluorescent FAST-tagged proteins using metabolically engineered strains of Eubacterium limosum.

Background: The interest in using methanol as a substrate to cultivate acetogens increased in recent years since it can be sustainably produced from syngas and has the additional benefit of reducing greenhouse gas emissions. Eubacterium limosum is one of the few acetogens that can utilize methanol, is genetically accessible and, therefore, a promising candidate for the recombinant production of biocommodities from this C1 carbon source. Although several genetic tools are already available for certain acetogens including E.

Isobutanol Production by Autotrophic Acetogenic Bacteria.

Two different isobutanol synthesis pathways were cloned into and expressed in the two model acetogenic bacteria and . is specialized on using CO + H gas mixtures for growth and depends on sodium ions for ATP generation by a respective ATPase and Rnf system. On the other hand, grows well on syngas (CO + H + CO mixture) and depends on protons for energy conservation.

Identifying and Engineering Bottlenecks of Autotrophic Isobutanol Formation in Recombinant by Systemic Analysis.

(, CLJU) is natively endowed producing acetic acid, 2,3-butandiol, and ethanol consuming gas mixtures of CO, CO, and H (syngas). Here, we present the syngas-based isobutanol formation using harboring the recombinant amplification of the "Ehrlich" pathway that converts intracellular KIV to isobutanol. Autotrophic isobutanol production was studied analyzing two different strains in 3-L gassed and stirred bioreactors.

Electron availability in CO , CO and H mixtures constrains flux distribution, energy management and product formation in Clostridium ljungdahlii.

Acetogens such as Clostridium ljungdahlii can play a crucial role reducing the human CO footprint by converting industrial emissions containing CO , CO and H into valuable products such as organic acids or alcohols. The quantitative understanding of cellular metabolism is a prerequisite to exploit the bacterial endowments and to fine-tune the cells by applying metabolic engineering tools. Studying the three gas mixtures CO  + H , CO and CO + CO  + H (syngas) by continuously gassed batch cultivation experiments and applying flux balance analysis, we identified CO as the preferred carbon and electron source for growth and producing alcohols.

gen. nov., sp. nov., a new caproate-producing bacterium and emended description of the genus .

A strictly anaerobic bacterial strain designated EA1 was isolated from an enrichment culture inoculated with biogas reactor content. Cells of strain EA1 are spore-forming rods (1-3×0.4-0.

Induced heterologous expression of the arginine deiminase pathway promotes growth advantages in the strict anaerobe Acetobacterium woodii.

The advantage of using acetogens such as Acetobacterium woodii as biocatalysts converting the cheap substrate and greenhouse gas carbon dioxide (CO) into value-added chemicals comes together with the disadvantage of a low overall ATP gain due to the bioenergetics associated with the Wood-Ljungdahl pathway. Expanding the product spectrum of recombinant A. woodii strains to compounds with high ATP-demanding biosynthesis is therefore challenging.

Genome Sequence of the Caproic Acid-Producing Bacterium Caproiciproducens galactitolivorans BS-1 (JCM 30532).

BS-1 is an anaerobic bacterium that produces acetate, butyrate, and caproate. The genome has a size of 2.57 Mbp and harbors 2,439 predicted protein-coding genes.

Anaerobic Production of Poly(3-hydroxybutyrate) and Its Precursor 3-Hydroxybutyrate from Synthesis Gas by Autotrophic Clostridia.

Anaerobic production of the biopolymer poly(3-hydroxybutyrate) (PHB) and the monomer 3-hydroxybutyrate (3-HB) was achieved using recombinant clostridial acetogens supplied with syn(thesis) gas as the sole carbon and energy source. 3-HB production was successfully accomplished by a new synthetic pathway containing the genes (encoding thiolase A), (encoding CoA-transferase A/B), and (encoding ()-3-hydroxybutyrate dehydrogenase). The respective recombinant [p83_tcb] strain produced autotrophically 0.

Different response of bacteria, archaea and fungi to process parameters in nine full-scale anaerobic digesters.

Biogas production is a biotechnological process realized by complex bacterial, archaeal and likely fungal communities. Their composition was assessed in nine full-scale biogas plants with distinctly differing feedstock input and process parameters. This study investigated the actually active microbial community members by using a comprehensive sequencing approach based on ribosomal 16S and 28S rRNA fragments.

Bacterial Anaerobic Synthesis Gas (Syngas) and CO+H Fermentation.

Anaerobic bacterial gas fermentation gains broad interest in various scientific, social, and industrial fields. This microbial process is carried out by a specific group of bacterial strains called acetogens. All these strains employ the Wood-Ljungdahl pathway but they belong to different taxonomic groups.

Using gas mixtures of CO, CO and H as microbial substrates: the do's and don'ts of successful technology transfer from laboratory to production scale.

The reduction of CO emissions is a global effort which is not only supported by the society and politicians but also by the industry. Chemical producers worldwide follow the strategic goal to reduce CO emissions by replacing existing fossil-based production routes with sustainable alternatives. The smart use of CO and CO /H mixtures even allows to produce important chemical building blocks consuming the said gases as substrates in carboxydotrophic fermentations with acetogenic bacteria.

Gas fermentation for commodity chemicals and fuels.

Gas fermentation is a microbial process that contributes to at least four of the sustainable development goals (SDGs) of the United Nations. The process converts waste and greenhouse gases into commodity chemicals and fuels. Thus, world's climate is positively affected.

Complete Genome Sequence of the Autotrophic Acetogen DSM 92 Using Nanopore and Illumina Sequencing Data.

Here, we report the closed genome sequence of , an Rnf- and cytochrome-containing autotrophic acetogen that is able to convert carbon monoxide to acetate using the Wood-Ljungdahl pathway. The genome consists of a circular chromosome (4.59 Mb).