Identification of acrylate, the product of the dehydration of (<i>R</i>)‐lactate catalysed by cell‐free extracts from <i>Clostridium propionicum</i>

Schweiger, Georg

doi:10.1016/0014-5793(85)80917-0

Cited by 31 publications

(20 citation statements)

References 10 publications

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“…Clostridia have been shown to convert cysteine to acetate by two mechanisms that do not involve key enzymes of the Wood pathway. Clostridium propionicurn degrades cysteine to propionate and acetate through acrylate as an intermediate (42). Some clostridia deaminate cysteine to pyruvate by a cysteine desulfhydralase and convert pyruvate to acetate via acetyl coenzyme A (1).…”

Section: Discussionmentioning

confidence: 99%

Clostridium ultunense sp. nov., a Mesophilic Bacterium Oxidizing Acetate in Syntrophic Association with a Hydrogenotrophic Methanogenic Bacterium

Schnürer

Schink²,

Svensson³

1996

International Journal of Systematic Bacteriology

286

216

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A syntrophic acetate-oxidizing bacterium, strain BST (T = type strain), was isolated from a previously described mesophilic triculture that was able to syntrophically oxidize acetate and form methane in stoichiometric amounts. Strain BST was isolated with substrates typically utilized by homoacetogenic bacteria. Strain BST was a spore-forming, gram-positive, rod-shaped organism which utilized formate, glucose, ethylene glycol, cysteine, betaine, and pyruvate. Acetate and sometimes formate were the main fermentation products. Small amounts of alanine were also produced from glucose, betaine, and cysteine. Strain BST grew optimally at 37°C and pH 7. The G+C content of the DNA of strain BST was 32 mol%. A 16s rRNA sequence analysis revealed that strain BST was a member of a new species of the genus Closfridium. We propose the name Clostridium ultunense for this organism; strain BS is the type strain of C. ultunense.Anaerobic oxidations of fatty acids to hydrogen and carbon dioxide by proton-reducing bacteria are, from a thermodynamic point of view, very unfavorable reactions (38). Under standard conditions, these hydrogen-producing reactions are all endergonic. However, standard conditions are not the conditions that occur in most natural anaerobic environments; at a very low partial pressure of hydrogen, like the partial pressure achieved in the presence of hydrogenotrophs, such as methanogenic or sulfate-reducing bacteria, the oxidation reaction becomes exergonic (9, 48). By consuming hydrogen, the hydrogenotrophs can create conditions under which the protonreducing bacteria can perform oxidations that otherwise could not yield energy; i.e., the latter organisms depend entirely on the former to fulfill their function.Several different species of bacteria are able to oxidize fatty acids (38). Syntrophomonas wolfei degrades straight-chain fatty acids up to octanoate, forming acetate and propionate together with H,, in cocultures with either a methanogen or a sulfate reducer (25). Propionate is degraded to acetate, carbon dioxide, and H, by Syntrophobacter wolinii in cocultures with members of the genus Desulfovibrio (5). Clostridium blyantii oxidizes fatty acids with 4 to 11 carbon atoms in associations with several different hydrogen-utilizing bacteria (43). Acetic acid is associated with the lowest levels of energy released from the fatty acids degraded in syntrophic cooperations. Thus, the partial pressure of hydrogen has to be very low for this reaction to proceed, and the energy available is influenced by the electron acceptor used. Under standard conditions, acetate oxidation coupled to methane formation releases less energy than acetate oxidation coupled to sulfate reduction (AGO' = -31.0 kJ/mol and AGO' = -47.7 kJ/mol, respectively). The changes in free energy are also slightly greater at higher temperatures. Syntrophic oxidation of acetate has been observed with thermophilic and mesophilic cultures, as well as at moderate tem- peratures with both methanogenic and sulfate-reducing bacteria as the hydrogen-c...

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Section: Discussionmentioning

confidence: 99%

Clostridium ultunense sp. nov., a Mesophilic Bacterium Oxidizing Acetate in Syntrophic Association with a Hydrogenotrophic Methanogenic Bacterium

Schnürer

Schink²,

Svensson³

1996

International Journal of Systematic Bacteriology

286

216

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“…Acrylate has also been shown to serve as a terminal electron acceptor for Desulfovibrio acrylicus, producing propionate which is not further metabolized as a growth substrate (31). Cell extracts of C. propionicum have been shown to dehydrate (R)-lactate to acrylate (20), suggesting that the reverse reaction could be another strategy for acrylate catabolism. Figure 1 summarizes the deamidation reaction that produces acrylic acid from acrylamide and possible subsequent fates of acrylate.…”

mentioning

confidence: 99%

Photoheterotrophic Metabolism of Acrylamide by a Newly Isolated Strain of Rhodopseudomonas palustris

Wampler

Ensign

2005

Appl Environ Microbiol

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Acrylamide, a neurotoxin and suspected carcinogen, is produced by industrial processes and during the heating of foods. In this study, the microbial diversity of acrylamide metabolism has been expanded through the isolation and characterization of a new strain of Rhodopseudomonas palustris capable of growth with acrylamide under photoheterotrophic conditions. The newly isolated strain grew rapidly with acrylamide under photoheterotrophic conditions (doubling time of 10 to 12 h) but poorly under anaerobic dark or aerobic conditions. Acrylamide was rapidly deamidated to acrylate by strain Ac1, and the subsequent degradation of acrylate was the rate-limiting reaction in cell growth. Acrylamide metabolism by succinate-grown cultures occurred only after a lag period, and the induction of acrylamide-degrading activity was prevented by the presence of protein or RNA synthesis inhibitors. 13 Acrylamide is a toxic three-carbon compound containing an amide group and an ␣,␤-unsaturated olefin bond. It exerts its toxic effects by forming adducts to nucleophilic moieties such as sulfhydryl groups on proteins (4). Acrylamide is potent neurotoxin (30) and suspected to be a carcinogen (21, 27). Although acrylamide is not typically found in nature, it is widely used in industrial processes as a polymerizing agent, hardener, and as a flocculent in water treatment. Accordingly, acrylamide released from industrial processes has resulted in the contamination of both soils and aquatic environments (6). Recently, it was discovered that acrylamide is formed in starchy foods after being cooked at the high temperatures required for frying and baking (26,27). These foods, which have undetectable levels before cooking, have acrylamide levels as high as 2.3 mg/kg after cooking (25). The formation of acrylamide is believed to be a product of the reaction between asparagine and glucose during the cooking process (14, 24).In spite of acrylamide's toxicity in the monomer form, some microorganisms are able to utilize acrylamide as their sole carbon source for growth (16,17,22,32,33). All studies conducted to date show that there is an initial deamidation step that converts acrylamide to acrylic acid (acrylate) (15,17,22,33). The subsequent fate of acrylate has not been well defined for acrylamideutilizing bacteria but probably involves pathways and enzymes that have been characterized to various degrees for other bacteria capable of acrylate catabolism. In aerobic acrylate-utilizing bacteria, acrylate metabolism has been shown to proceed via hydroxylation to ␤-hydroxypropionate, which is further oxidized to CO 2 (1, 2). Highlighting a different fate for acrylate under anaerobic conditions, Clostridium propionicum is capable of fermenting acrylate to acetate and propionate (10). Acrylate has also been shown to serve as a terminal electron acceptor for Desulfovibrio acrylicus, producing propionate which is not further metabolized as a growth substrate (31). Cell extracts of C. propionicum have been shown to dehydrate (R)-lactate to acrylate (20)...

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“…The equilibrium ratio [acrylyl-CoA]/[lactoyl-CoA] is only about 0.005. 260 The molar ratio [acrylate]/[lactate] was found to be approximately 0.03 at equilibrium. 261 Equilibrium limitations will also play a role if 3-hydroxypropionate is used for enzymatic acrylic acid production, because cultivation of R. erythropolis LG12 with 40 g/L of acrylic acid resulted in 44% conversion into 3-hydroxypropionate.…”

Section: Acrylic Acidmentioning

confidence: 98%

Transformation of Biomass into Commodity Chemicals Using Enzymes or Cells

2013

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Identification of acrylate, the product of the dehydration of (R)‐lactate catalysed by cell‐free extracts from Clostridium propionicum

Cited by 31 publications

References 10 publications

Clostridium ultunense sp. nov., a Mesophilic Bacterium Oxidizing Acetate in Syntrophic Association with a Hydrogenotrophic Methanogenic Bacterium

Clostridium ultunense sp. nov., a Mesophilic Bacterium Oxidizing Acetate in Syntrophic Association with a Hydrogenotrophic Methanogenic Bacterium

Photoheterotrophic Metabolism of Acrylamide by a Newly Isolated Strain of Rhodopseudomonas palustris

Transformation of Biomass into Commodity Chemicals Using Enzymes or Cells

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