Recirculation of H2, CO2, and ethylene improves carbon fixation and carboxylate yields in anaerobic fermentation

Anaerobic fermentation with mixed cultures has gained momentum as a bioprocess for its promise to produce platform carboxylates from low-value biomass feedstocks. Anaerobic fermenters are net carbon emitters and their carboxylate yields are limited by electron donor availability. In a new approach to tackle these two disadvantages, we operated two bioreactors fed with acetate and lactate as a model feedstock while recirculating H2/CO2 to stimulate concomitant autotrophic activity. After 42 days of operation, hydrogenotrophic methanogenesis was predominant and ethylene (≥1.3 kPa) was added to one of the reactors, inhibiting methanogenesis completely and recovering net carbon fixation (0.20 g CO2 L-1 d-1). When methanogenesis was inhibited, exogenous H2 accounted for 17% of the consumed electron donors. Lactate-to-butyrate selectivity was 101% (88% in the control without ethylene) and lactate-to-caproate selectivity was 17% (2.3% in the control). Community analysis revealed that ethylene caused Methanobacterium to be washed out, giving room to acetogenic bacteria. In contrast to 2-bromoethanosulfonate, ethylene is a scalable methanogenesis inhibition strategy that did not collaterally block i-butyrate formation. By favoring the bacterial share of the community to become mixotrophic, the concept offers a way to simultaneously increase selectivity to medium-chain carboxylates and to develop a carbon-fixing chain elongation process.

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Metagenomics-guided analysis of microbial chemolithoautotrophic phosphite oxidation yields evidence of a seventh natural CO2fixation pathway

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.1715549114 ◽

2017 ◽

Vol 115 (1) ◽

pp. E92-E101 ◽

Cited By ~ 52

Author(s):

Israel A. Figueroa ◽

Tyler P. Barnum ◽

Pranav Y. Somasekhar ◽

Charlotte I. Carlström ◽

Anna L. Engelbrektson ◽

...

Keyword(s):

Wastewater Treatment ◽

16S Rrna ◽

Carbon Fixation ◽

Community Analysis ◽

Metabolic Model ◽

Rrna Gene ◽

Autotrophic Growth ◽

Anaerobic Wastewater Treatment ◽

Natural Carbon ◽

Environmental Relevance

Dissimilatory phosphite oxidation (DPO), a microbial metabolism by which phosphite (HPO32−) is oxidized to phosphate (PO43−), is the most energetically favorable chemotrophic electron-donating process known. Only one DPO organism has been described to date, and little is known about the environmental relevance of this metabolism. In this study, we used 16S rRNA gene community analysis and genome-resolved metagenomics to characterize anaerobic wastewater treatment sludge enrichments performing DPO coupled to CO2reduction. We identified an uncultivated DPO bacterium,CandidatusPhosphitivorax (Ca.P.) anaerolimi strain Phox-21, that belongs to candidate order GW-28 within theDeltaproteobacteria, which has no known cultured isolates. Genes for phosphite oxidation and for CO2reduction to formate were found in the genome ofCa.P. anaerolimi, but it appears to lack any of the known natural carbon fixation pathways. These observations led us to propose a metabolic model for autotrophic growth byCa.P. anaerolimi whereby DPO drives CO2reduction to formate, which is then assimilated into biomass via the reductive glycine pathway.

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Development of an enhanced chain elongation process for caproic acid production from waste-derived lactic acid and butyric acid

International Chain Elongation Conference 2020 ◽

10.18174/icec2020.18007 ◽

2020 ◽

Author(s):

Corine Nzeteu

Keyword(s):

Lactic Acid ◽

Butyric Acid ◽

Acid Production ◽

Caproic Acid ◽

Chain Elongation ◽

Elongation Process ◽

The Right

Contribution to the International Chain Elongation Conference 2020 | ICEC 2020. An abstract can be found in the right column.

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Recent progress in oligonucleotide synthesis.

Acta Biochimica Polonica ◽

10.18388/abp.1996_4515 ◽

1996 ◽

Vol 43 (1) ◽

pp. 37-44 ◽

Cited By ~ 9

Author(s):

W Pfleiderer ◽

S Matysiak ◽

F Bergmann ◽

R Schnell

Keyword(s):

Acid Catalysis ◽

Solid Phase ◽

Chain Elongation ◽

Synthetic Approach ◽

Blocking Group ◽

General Application ◽

Acidic Conditions ◽

Elongation Process ◽

Acid Labile ◽

Solid Phase Material

New blocking group combinations for the machine-aided oligoribonucleotide synthesis on solid phase material have been developed and tested regarding their general application. An acetal function for 2'-OH protection offers a series of advantages in the synthetic approach but special conditions have to be fulfilled in order to guarantee a selective cleavage of the temporary 5'-OH blocking group such as the dansylethoxycarbonyl or even the acid-labile dimethoxytrityl group in the chain elongation process. The final removal of the 2'-O-acetal function in the partially deblocked oligomer proceeds unexpectedly well under weak acidic conditions due to a supposed intramolecular acid catalysis.

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AcetoBase: a functional gene repository and database for formyltetrahydrofolate synthetase sequences

Database ◽

10.1093/database/baz142 ◽

2019 ◽

Vol 2019 ◽

Cited By ~ 1

Author(s):

Abhijeet Singh ◽

Bettina Müller ◽

Hans-Henrik Fuxelius ◽

Anna Schnürer

Keyword(s):

Carbon Fixation ◽

Sequence Data ◽

Gene Encoding ◽

Formyltetrahydrofolate Synthetase ◽

Protein Levels ◽

Acetogenic Bacteria ◽

Blast Database ◽

Key Enzyme ◽

Chemolithoautotrophic Bacteria ◽

Taxonomic Studies

Abstract Acetogenic bacteria are imperative to environmental carbon cycling and diverse biotechnological applications, but their extensive physiological and taxonomical diversity is an impediment to systematic taxonomic studies. Acetogens are chemolithoautotrophic bacteria that perform reductive carbon fixation under anaerobic conditions through the Wood–Ljungdahl pathway (WLP)/acetyl-coenzyme A pathway. The gene-encoding formyltetrahydrofolate synthetase (FTHFS), a key enzyme of this pathway, is highly conserved and can be used as a molecular marker to probe acetogenic communities. However, there is a lack of systematic collection of FTHFS sequence data at nucleotide and protein levels. In an attempt to streamline investigations on acetogens, we developed AcetoBase - a repository and database for systematically collecting and organizing information related to FTHFS sequences. AcetoBase also provides an opportunity to submit data and obtain accession numbers, perform homology searches for sequence identification and access a customized blast database of submitted sequences. AcetoBase provides the prospect to identify potential acetogenic bacteria, based on metadata information related to genome content and the WLP, supplemented with FTHFS sequence accessions, and can be an important tool in the study of acetogenic communities. AcetoBase can be publicly accessed at https://acetobase.molbio.slu.se.

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Hydrogenotrophic methanogenesis in archaeal phylum Verstraetearchaeota reveals the shared ancestry of all methanogens

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.1815631116 ◽

2019 ◽

Vol 116 (11) ◽

pp. 5037-5044 ◽

Cited By ~ 66

Author(s):

Bojk A. Berghuis ◽

Feiqiao Brian Yu ◽

Frederik Schulz ◽

Paul C. Blainey ◽

Tanja Woyke ◽

...

Keyword(s):

Paradigm Shift ◽

Carbon Fixation ◽

Methanogenic Archaea ◽

Global Carbon Cycle ◽

Hydrogenotrophic Methanogenesis ◽

Shared Ancestry ◽

Hydrogenotrophic Methanogens ◽

Methyl Coenzyme M Reductase ◽

Global Carbon ◽

Insight Into

Methanogenic archaea are major contributors to the global carbon cycle and were long thought to belong exclusively to the euryarchaeal phylum. Discovery of the methanogenesis gene cluster methyl-coenzyme M reductase (Mcr) in the Bathyarchaeota, and thereafter the Verstraetearchaeota, led to a paradigm shift, pushing back the evolutionary origin of methanogenesis to predate that of the Euryarchaeota. The methylotrophic methanogenesis found in the non-Euryarchaota distinguished itself from the predominantly hydrogenotrophic methanogens found in euryarchaeal orders as the former do not couple methanogenesis to carbon fixation through the reductive acetyl-CoA [Wood–Ljungdahl pathway (WLP)], which was interpreted as evidence for independent evolution of the two methanogenesis pathways. Here, we report the discovery of a complete and divergent hydrogenotrophic methanogenesis pathway in a thermophilic order of the Verstraetearchaeota, which we have named Candidatus Methanohydrogenales, as well as the presence of the WLP in the crenarchaeal order Desulfurococcales. Our findings support the ancient origin of hydrogenotrophic methanogenesis, suggest that methylotrophic methanogenesis might be a later adaptation of specific orders, and provide insight into how the transition from hydrogenotrophic to methylotrophic methanogenesis might have occurred.

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Production of a newly discovered PHA family member with an isobutyrate-fed enrichment culture

Applied Microbiology and Biotechnology ◽

10.1007/s00253-021-11742-9 ◽

2022 ◽

Author(s):

Chris M. Vermeer ◽

Larissa J. Bons ◽

Robbert Kleerebezem

Keyword(s):

Family Member ◽

Metabolic Pathways ◽

Volatile Fatty Acids ◽

Anaerobic Fermentation ◽

Enrichment Culture ◽

Dry Weight ◽

Chain Elongation ◽

Structural Isomer ◽

Distinct Character ◽

Pha Production

Abstract Using microbial enrichment cultures for the production of waste-derived polyhydroxyalkanoates (PHAs) is a promising technology to recover secondary resources. Volatile fatty acids (VFAs) form the preferred substrate for PHA production. Isobutyrate is a VFA appearing in multiple waste valorization routes, such as anaerobic fermentation, chain elongation, and microbial electrosynthesis, but has never been assessed individually on its PHA production potential. This research investigates isobutyrate as sole carbon source for a microbial enrichment culture in comparison to its structural isomer butyrate. The results reveal that the enrichment of isobutyrate has a very distinct character regarding microbial community development, PHA productivity, and even PHA composition. Although butyrate is a superior substrate in almost every aspect, this research shows that isobutyrate-rich waste streams have a noteworthy PHA-producing potential. The main finding is that the dominant microorganism, a Comamonas sp., is linked to the production of a unique PHA family member, poly(3-hydroxyisobutyrate) (PHiB), up to 37% of the cell dry weight. This is the first scientific report identifying microbial PHiB production, demonstrating that mixed microbial communities can be a powerful tool for discovery of new metabolic pathways and new types of polymers. Key points • PHiB production is a successful storage strategy in an isobutyrate-fed SBR • Isomers isobutyrate and butyrate reveal a very distinct PHA production behavior • Enrichments can be a tool for discovery of new metabolic pathways and polymers Graphical abstract

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Effect of ultrasonic pretreatment on chain elongation of saccharified residue from food waste by anaerobic fermentation

Environmental Pollution ◽

10.1016/j.envpol.2020.115936 ◽

2021 ◽

Vol 268 ◽

pp. 115936 ◽

Cited By ~ 1

Author(s):

Hongzhi Ma ◽

Yujia Lin ◽

Yong Jin ◽

Ming Gao ◽

Hongai Li ◽

...

Keyword(s):

Food Waste ◽

Anaerobic Fermentation ◽

Chain Elongation ◽

Ultrasonic Pretreatment

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New approach to peptide chain elongation in the N-C-direction in solid phase synthesis (‘inverse synthesis’)

Peptides 1994 ◽

10.1007/978-94-011-1468-4_83 ◽

1995 ◽

pp. 201-202 ◽

Cited By ~ 1

Author(s):

E. Bayer ◽

B. Henkel ◽

L. Zhang ◽

N. Clausen ◽

C. Goldammer ◽

...

Keyword(s):

Solid Phase Synthesis ◽

Solid Phase ◽

Peptide Chain ◽

Chain Elongation ◽

New Approach ◽

Phase Synthesis

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Three Novel Clostridia Isolates Produce n-Caproate and iso-Butyrate from Lactate: Comparative Genomics of Chain-Elongating Bacteria

Microorganisms ◽

10.3390/microorganisms8121970 ◽

2020 ◽

Vol 8 (12) ◽

pp. 1970

Author(s):

Bin Liu ◽

Denny Popp ◽

Nicolai Müller ◽

Heike Sträuber ◽

Hauke Harms ◽

...

Keyword(s):

Comparative Genomics ◽

Energy Conservation ◽

Core Genome ◽

Anaerobic Fermentation ◽

Batch Cultivation ◽

Chain Elongation ◽

Hydrogen Formation ◽

Lactate Oxidation ◽

Platform Chemicals ◽

Genome Heterogeneity

The platform chemicals n-caproate and iso-butyrate can be produced by anaerobic fermentation from agro-industrial residues in a process known as microbial chain elongation. Few lactate-consuming chain-elongating species have been isolated and knowledge on their shared genetic features is still limited. Recently we isolated three novel clostridial strains (BL-3, BL-4, and BL-6) that convert lactate to n-caproate and iso-butyrate. Here, we analyzed the genetic background of lactate-based chain elongation in these isolates and other chain-elongating species by comparative genomics. The three strains produced n-caproate, n-butyrate, iso-butyrate, and acetate from lactate, with the highest proportions of n-caproate (18%) for BL-6 and of iso-butyrate (23%) for BL-4 in batch cultivation at pH 5.5. They show high genomic heterogeneity and a relatively small core-genome size. The genomes contain highly conserved genes involved in lactate oxidation, reverse β-oxidation, hydrogen formation and either of two types of energy conservation systems (Rnf and Ech). Including genomes of another eleven experimentally validated chain-elongating strains, we found that the chain elongation-specific core-genome encodes the pathways for reverse β-oxidation, hydrogen formation and energy conservation, while displaying substantial genome heterogeneity. Metabolic features of these isolates are important for biotechnological applications in n-caproate and iso-butyrate production.

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