Microbial co-cultivation induces a metabolic shift, promoting syngas conversion to chain-elongated acids

Introduction: Syngas, a mixture of H2, CO and CO2, can be generated from a wide range of (low-biodegradable wastes) and is a suitable feedstock for biotechnological processes. Several microorganisms are able to use syngas for growth, but main natural products from this fermentation are acetate and ethanol. In order to extend the range of products from syngas fermentation, we constructed a synthetic co-culture of Clostridium autoethanogenum, a carboxydotrophic acetogen, with Clostridium kluyveri, a bacterium employing the reverse -oxidation pathwaya. C. autoethanogenum converted syngas to acetate and ethanol, and C. kluyveri elongated these products to butyrate and caproate. Methods: Experiments in batch bottles and chemostats were conducted to study the differences in physiological behavior between monocultures of C. autoethanogenum and co-cultures of C. autoethanogenum and C. kluyveri. In addition to physiological characterization a transcriptomics approach was used to unravel the molecular functioning of this co-cultureb. Results: Expression of the central carbon- and energy-metabolism of C. autoethanogenum in pure or in co-culture with C. kluyveri remained unaltered. However, the electron flux from CO to intermediate products (acetate/ethanol) was substantially shifted towards the production of ethanol. In co-culture conditions fed with additional acetate, the metabolism of C. autoethanogenum could be pushed to produce only ethanol from CO, resulting in high yields of chain elongated acids by the co-culture. Conclusions: The results suggest that thermodynamics and metabolic dependence between the two strains, rather than gene expression, plays a key role in the ratio of products formed during CO fermentation by C. autoethanogenum. Overall this suggests that microbial interactions can be exploited to steer the syngas fermentation process towards products of interest, enhancing both the efficiency and the products spectrum of syngas fermentation technology.info:eu-repo/semantics/publishedVersio

The role of ethanol oxidation during carboxydotrophic growth of clostridium autoethanogenum

The WoodLjungdahl pathway is an ancient metabolic route used by acetogenic carboxydotrophs to convert CO into acetate, and some cases ethanol. When produced, ethanol is generally seen as an end product of acetogenic metabolism, but here we show that it acts as an important intermediate and co-substrate during carboxydotrophic growth of Clostridium autoethanogenum. Depending on CO availability, C. autoethanogenum is able to rapidly switch between ethanol production and utilization, hereby optimizing its carboxydotrophic growth. The importance of the aldehyde ferredoxin:oxidoreductase (AOR) route for ethanol production in carboxydotrophic acetogens is known; however, the role of the bifunctional alcohol dehydrogenase AdhE (AldAdh) route in ethanol metabolism remains largely unclear. We show that the mutant strain C. autoethanogenum adhE1a, lacking the Ald subunit of the main bifunctional aldehyde/alcohol dehydrogenase (AdhE, CAETHG\_3747), has poor ethanol oxidation capabilities, with a negative impact on biomass yield. This indicates that the AdhAld route plays a major role in ethanol oxidation during carboxydotrophic growth, enabling subsequent energy conservation via substrate-level phosphorylation using acetate kinase. Subsequent chemostat experiments with C. autoethanogenum show that the wild type, in contrast to adhE1a, is more resilient to sudden changes in CO supply and utilizes ethanol as a temporary storage for reduction equivalents and energy during CO-abundant conditions, reserving these stored assets for more CO-limited conditions. This shows that the direction of the ethanol metabolism is very dynamic during carboxydotrophic acetogenesis and opens new insights in the central metabolism of C. autoethanogenum and similar acetogens.info:eu-repo/semantics/publishedVersio

Microbial propionate production from carbon monoxide a novel bioprocess

Introduction: The fermentation of CO-rich gases by carboxidotrophic microbes is a promising way to produce valuable organic compounds. Propionate is a value-added compound with numerous industrial applications, e.g. as an antifungal agent in food and feed, and as a building block to produce plastics and herbicides. Propionate is currently produced by petrochemical processes, but it can be produced from ethanol and acetate by some propionogenic bacteria. Ethanol and acetate are usually formed by acetogenic bacteria from CO-rich gases. Accordingly, propionate can be indirectly produced from CO-rich gases, representing a new approach on the realm of microbial CO conversion. Methodology: Four distinct synthetic co-cultures were constructed, consisting of: Acetobacterium wieringae (DSM 1911T) and Pelobacter propionicus (DSM 2379T); A. wieringae (DSM 1911T) and Anaerotignum neopropionicum (DSM 3847T); A. wieringae strain JM and P. propionicus (DSM 2379T); A. wieringae strain JM and A. neopropionicum (DSM 3847T). The physiology of CO conversion to propionate was accessed and a proteogenomic analysis was performed in the best performing co-culture to get insight into the involved biochemical pathways and microbial interactions within the synthetic consortium. Results: Propionate was produced by all the co-cultures, with the highest titer (~24 mM) measured in the co-culture composed of A. wieringae strain JM + A. neopropionicum, which also produced isovalerate (~4 mM), butyrate (~1 mM), and isobutyrate (~0.3 mM). In this synthetic consortium, A. wieringae strain JM converts CO to a acetate and ethanol via the Wood-Ljungdahl pathway; acetate can also be converted to ethanol through the action of aldehyde oxidoreductase (AOR); A. neopropionicum converts ethanol to propionate via the acrylate pathway. In addition, proteins related to amino acid metabolism and stress response were highly abundant during co-cultivation, which raises the hypothesis that amino acids are exchanged by the two microorganisms, and this results in isovalerate and isobutyrate production. Conclusions: This synthetic co-culture represents a new bioprocess for the microbial production of propionate from carbon monoxide, that couples the Wood-Ljungdahl and acrylate pathways. Furthermore, this symbiosis engages an interesting perspective on how C1-fixing and C3-producing microorganisms can be used to expand the product scope of gas fermentation.Portuguese Foundation for Science and Technology (FCT): POCI-01-0145-FEDER-031377; strategic funding of UIDB/04469/2020 unit; BioTecNorte operation (NORTE-01-0145-FEDER-000004); FCT doctoral grants PD/BD/128030/2016 and PD/BD/150583/2020. Netherlands Science Foundation (NWO): Project NWO-GK-07; Perspectief Programma P16-10; Gravitation Grant, Project 024.002.002.info:eu-repo/semantics/publishedVersio

Production of propionate from carbon monoxide by a synthetic co-culture

info:eu-repo/semantics/publishedVersio

Enrichment of anaerobic syngas-converting communities and isolation of a novel carboxydotrophic Acetobacterium wieringae strain jm

The datasets generated for this study can be found in the 16S rRNA gene sequences submitted to the European Nucleotide Database (ENA) accession numbers LR655884, LR657299 to LR657303, PRJEB33623. The Whole Genome Shotgun project of Acetobacterium wieringae strain JM has been deposited at DDBJ/ENA/GenBank under the accession VSLA00000000.Syngas is a substrate for the anaerobic bioproduction of fuels and valuable chemicals. In this study, anaerobic sludge was used for microbial enrichments with synthetic syngas and acetate as main substrates. The objectives of this study were to identify microbial networks (in enrichment cultures) for the conversion of syngas to added-value products, and to isolate robust, non-fastidious carboxydotrophs. Enrichment cultures produced methane and propionate, this last one an unusual product from syngas fermentation. A bacterium closely related to Acetobacterium wieringae was identified as most prevalent (87% relative abundance) in the enrichments. Methanospirillum sp. and propionate-producing bacteria clustering within the genera Anaerotignum and Pelobacter were also found. Further on, strain JM, was isolated and was found to be 99% identical (16S rRNA gene) to A. wieringae DSM 1911T. Digital DNA-DNA hybridization (dDDH) value between the genomes of strain JM and A. wieringae was 77.1%, indicating that strain JM is a new strain of A. wieringae. Strain JM can grow on carbon monoxide (100% CO, total pressure 170 kPa) without yeast extract or formate, producing mainly acetate. Remarkably, conversion of CO by strain JM showed shorter lag phase than in cultures of A. wieringae DSM 1911T, and about four times higher amount of CO was consumed in 7 days. Genome analysis suggests that strain JM uses the Wood-Ljungdahl pathway for the conversion of one carbon compounds (CO, formate, CO2/H2). Genes encoding bifurcational enzyme complexes with similarity to the bifurcational formate dehydrogenase (Fdh) of Clostridium autoethanogenum are present, and possibly relate to the higher tolerance to CO of strain JM compared to other Acetobacterium species. A. wieringae DSM 1911T grew on CO in medium containing 1 mM formate.The involved research was financially supported by Project NWO-GK-07 from the Netherlands Science Foundation (NWO), a Gravitation Grant (Project 024.002.002) of the Netherlands Ministry of Education, Culture and Science, and by the Portuguese Foundation for Science and Technology (FCT) under the scope of the strategic funding of UIDB/04469/2020 unit and BioTecNorte operation (NORTE-01-0145-FEDER-000004) funded by the European Regional Development Fund under the scope of Norte2020–Programa Operacional Regional do Norte. The financial support from FCT and European Social Fund (POPH-QREN) through the grant PD/BD/128030/2016 given to AA, and through the project INNOVsyn – Innovative strategies for syngas fermentation (POCI-01-0145-FEDER-031377), are gratefully acknowledged.info:eu-repo/semantics/publishedVersio

Propionate production from carbon monoxide by synthetic cocultures of acetobacterium wieringae and propionigenic bacteria

Gas fermentation is a promising way to convert CO-rich gases to chemicals. We studied the use of synthetic cocultures composed of carboxydotrophic and propionigenic bacteria to convert CO to propionate. So far, isolated carboxydotrophs cannot directly ferment CO to propionate, and therefore, this cocultivation approach was investigated. Four distinct synthetic cocultures were constructed, consisting of Acetobacterium wieringae (DSM 1911T) and Pelobacter propionicus (DSM 2379T), Ac. wieringae (DSM 1911T) and Anaerotignum neopropionicum (DSM 3847T), Ac. wieringae strain JM and P. propionicus (DSM 2379T), and Ac. wieringae strain JM and An. neopropionicum (DSM 3847T). Propionate was produced by all the cocultures, with the highest titer (;24mM) being measured in the coculture composed of Ac. wieringae strain JM and An. neopropionicum, which also produced isovalerate (;4mM), butyrate (;1mM), and isobutyrate (0.3mM). This coculture was further studied using proteogenomics. As expected, enzymes involved in the Wood-Ljungdahl pathway in Ac. wieringae strain JM, which are responsible for the conversion of CO to ethanol and acetate, were detected; the proteome of An. neopropionicum confirmed the conversion of ethanol to propionate via the acrylate pathway. In addition, proteins related to amino acid metabolism and stress response were highly abundant during cocultivation, which raises the hypothesis that amino acids are exchanged by the two microorganisms, accompanied by isovalerate and isobutyrate production. This highlights the importance of explicitly looking at fortuitous microbial interactions during cocultivation to fully understand coculture behavior.This research was financially supported by Project NWO-GK-07 from the Netherlands Science Foundation (NWO), the Perspectief Programma P16-10 from NWO Applied and Engineering Sciences (AGS), by a Gravitation Grant (Project 024.002.002) of the Netherlands Ministry of Education, Culture and Science, and by the Portuguese Foundation for Science and Technology (FCT) under the scope of the strategic funding of UIDB/04469/2020 unit and BioTecNorte operation (NORTE-01-0145-FEDER-000004) funded by the European Regional Development Fund under the scope of Norte2020— Programa Operacional Regional do Norte. The financial support from FCT and European Social Fund (POPH-QREN) through the grant PD/BD/128030/2016 (given to Ana Luísa Arantes) and PD/BD/150583/2020 (given to João P. C. Moreira) and through the project INNOVsyn—Innovative strategies for syngas fermentation (POCI-01-0145-FEDER-031377) are gratefully acknowledged.info:eu-repo/semantics/publishedVersio

Restraining of glycoprotein VI- and integrin α2β1-dependent thrombus formation y platelet PECAM1

The platelet receptors, glycoprotein VI (GPVI) and integrin α2β1 jointly control collagen-dependent thrombus formation via protein tyrosine kinases. It is unresolved to which extent the ITIM (immunoreceptor tyrosine-based inhibitory motif) receptor PECAM1 and its downstream acting protein tyrosine phosphatase PTPN11 interfere in this process. Here, we hypothesized that integrin α2β1 has a co-regulatory role in the PECAM1- and PTPN11-dependent restraint of thrombus formation. We investigated platelet activation under flow on collagens with a different GPVI dependency and using integrin α2β1 blockage. Blood was obtained from healthy subjects and from patients with Noonan syndrome with a gain-of-function mutation of PTPN11 and variable bleeding phenotype. On collagens with decreasing GPVI activity (types I, III, IV), the surface-dependent inhibition of PECAM1 did not alter thrombus parameters using control blood. Blockage of α2β1 generally reduced thrombus parameters, most effectively on collagen IV. Strikingly, simultaneous inhibition of PECAM1 and α2β1 led to a restoration of thrombus formation, indicating that the suppressing signaling effect of PECAM1 is masked by the platelet-adhesive receptor α2β1. Blood from 4 out of 6 Noonan patients showed subnormal thrombus formation on collagen IV. In these patients, effects of α2β1 blockage were counterbalanced by PECAM1 inhibition to a normal phenotype. In summary, we conclude that the suppression of GPVI-dependent thrombus formation by either PECAM1 or a gain-of-function of PTPN11 can be overruled by α2β1 engagement

Production of medium-chain fatty acids and higher alcohols by a synthetic co-culture grown on carbon monoxide or syngas

Synthesis gas, a mixture of CO, H2, and CO2, is a promising renewable feedstock for bio-based production of organic chemicals. Production of medium-chain fatty acids can be performed via chain elongation, utilizing acetate and ethanol as main substrates. Acetate and ethanol are main products of syngas fermentation by acetogens. Therefore, syngas can be indirectly used as a substrate for the chain elongation process.ERC Grant (Project 323009) and the Gravitation Grant (Project 024.002.002) of the Netherlands Ministry of Education, Culture and Science, and the Netherlands Science Foundation (NWO

Proteomic analysis of the hydrogen and carbon monoxide metabolism of Methanothermobacter marburgensis

Hydrogenotrophic methanogenic archaea are efficient H2 utilizers, but only a few are known to be able to utilize CO. Methanothermobacter thermoautotrophicus is one of the hydrogenotrophic methanogens able to grow on CO, albeit about 100 times slower than on H2 + CO2. In this study we show that the hydrogenotrophic methanogen Methanothermobacter marburgensis, is able to perform methanogenic growth on H2/CO2/CO and on CO as a sole substrate. To gain further insight in its carboxydotrophic metabolism, the proteome of M. marburgensis, grown on H2/CO2 and H2/CO2/CO, was analysed. Cultures grown with H2/CO2/CO showed relative higher abundance of enzymes involved in the reductive acetyl-CoA pathway and proteins involved in redox metabolism. The data suggest that the strong reducing capacity of CO negatively affects hydrogenotrophic methanogenesis, making growth on CO as a sole substrate difficult for this type of methanogens. M. marburgensis appears to partly deal with this by upregulating co-factor regenerating reactions and activating additional pathways allowing for formation of other products, like acetate.Research of AS is supported by an ERC grant (project 323009) and a Gravitation grant (project024.002.002)of the Netherlands Ministry of Education, Culture and Science and the Netherlands Science Foundation (NWO)