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Oxidative metabolism of phthalic acid by soil Pseudomonads

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... A soil Pseudomonas sp. degraded o-phthalic acid through the formation of 4,5-dihydroxyphthalate and pro- tocatechuate [6]. Isophthalic acid was degraded through the formation of protocatechuate by a soil bacterium [7]. ...
... Generally phthalate isomers are degraded via introduction of two hydroxyl groups either at 3,4 or 4,5 position by the aerobic organisms [6][7][8]. The metabolism of homophthalate by the isolated strain follows a different pathway. ...
Article
A microorganism capable of degrading homophthalic acid as a sole source was isolated from garden soil. The strain was identified as Pseudomonas alcaligenes. The organism degraded homphthalate by a pathway which involved phenylactate and p-hydroxyphenylacetate as intermediates. The intermediates have been identified by physico-chemical methods. A tentative pathway for the degradation of homophthalate is proposed based on isolation of intermediates, oxygen uptake studies and presence of enzymes involved in the degradation.
... The degradation of phthalate isomers and phthalate esters has been studied extensively in various microorganisms [2][3][4][5]. In a soil Pseudomonas sp. and in Pseudomonas testosteroni, 4,5-dihydroxyphthalic acid and protocatechuic acid were shown to be the intermediates in o-phthalate metabolism [6,7]. A Micrococcus sp. was found to degrade o-phthalic acid via 3,4-dihydroxyphthalate and protocatechuate [8], whereas a Bacillus sp. was shown to initially decarboxylate o-phthalic acid to benzoate, which is further converted to gentisic acid, a substrate for ring cleavage [9]. ...
... The resuits provide evidence that terephthalate is probably metabolized via protocatechuate. Protocatechuate has been reported as an intermediate of 2 other phthalate isomers [3,6]. Several microorganisms employ initial double hydroxylation in aromatic acid and hydrocarbon metabolism, yielding dihydrodiol which is dehydrogenated in vivo to the corresponding orthodihydroxy compounds [21]. ...
Article
A Gram-positive bacterium with the ability to utilize terephthalic acid as sole carbon source was isolated from soil. The strain was identified as a Bacillus sp. Protocatechuate was shown to be a key intermediate in the degradation of terephthalate. Oxygen uptake studies were carried out with the probable intermediates. The presence of different enzymes was tested for. A mechanism is proposed for the degradation of terephthalate.
... The ease of phthalic acid biodegradation in nature fo llows the order: o-phthalate > terephthalate > isophthalate [7,24]. Aerobic bacteria use molecular oxygen as a cosubstrate to attack the stable aromatic ring of phthalate through dioxygenase-catalyzed addition of hydroxyl groups that faci litate decarboxylation to protocatechuate, a key intermediate of aerobic degradation of aromatic compounds 1253 (25)(26)(27)(28)(29). Aerobic phtha late degradation has been studi ed in detail. ...
... Oxidation of aromatic hydrocarbons by procaryotes and eucaryotes involves the conversion of such compounds into dihydroxyphenols, the prerequisite structures for ring fission. Either the elimination of substitute groups from the benzene nucleus (9,23) or the hydroxylation of a benzene nucleus can yield these dihydroxy compounds (8,12,16). In the case of eucaryotes, hydroxylation reactions are catalyzed by mono-oxygenases in the presence of reduced pyridine nucleotides with incorporation of a single atom of molecular oxygen into substrate molecule (17,26). ...
Article
A rumen isolate, Coprococcus, sp. Pe(1)5, was found to carry phloroglucinol reductase, which catalyzed the initial step in the breakdown of phloroglucinol. The organism uses phloroglucinol as the sole source of carbon and energy when grown in the absence of oxygen. Induced levels of enzyme were detected in cells grown either on phloroglucinol or on other carbon sources in the presence of limiting quantities of phloroglucinol. Although the organism is a strict anaerobe, the enzyme from anaerobically grown cells was insensitive to air. The partially purified enzyme required reduced nicotinamide adenine dinucleotide phosphate as an electron donor and was specific for phloroglucinol. However, partial enzyme activity (14 to 17%) was also detected in the presence of 2-methyl-1,4-naphthoquinone but not in the presence of several other phenolic compounds. The enzyme exhibited a higher affinity for phloroglucinol than for reduced nicotinamide adenine dinucleotide phosphate, with K(m) values of 3.0 x 10 M and 29.0 x 10 M, respectively. The optimum pH for maximal enzyme activity was 7.4, and the molecular weight of the native protein was about 130,000, as determined by the Sephadex gel filtration technique.
... The appearance of multiple UV absorption peaks during the metabolism of 2:3-PDCA by Strain OP-1 resembles changes that occur upon the conversion of phthalic acid to 4 : 5-dihydroxyphthalic acid [6,10]. The spectral changes probably indicate hydroxylated products since C5 and C6 of 2 : 3-PDCA are available for 4 : 5-dioxygenative attack. ...
Article
The prevalence of bacteria in the environment that catabolise synthetic phthalic acids (PAs) might be related to the natural occurrence of pyridine dicarboxylic acids (PDCAs). However, the bacterial metabolism of o-phthalic acid (phthalic acid) and its PDCA analogs was mostly exclusive. An exception was the oxidation of 2:3 and 3:4-PDCAs by a marine bacterium (Strain OP-1) when grown on phthalic acid. The metabolism of PDCAs by Strain OP-1 was induced by phthalic acid and, as for phthalate catabolism, the metabolism of 2:3-PDCA required Na+ ions.
... The degradation results in this study are in agreement with Hamzah et al., (2010), who observed that P. aerugenosa degraded 48% of light crude oil and up to 77% in 24h and 48h respectively. Ribbons and Evans, (1960) identified Pseudomonas to have the highest tolerance limit and degrading ability. In a related study of the degradation of phthalic acid by Pseudomonas and other soil microorganisms, Murad et al., (2007) found that Pseudomonas was able to degrade 72% of phthalic acid in 48 hours. ...
Article
In response to the quest for an environmentally friendly mode of disposal of shea nut cake, One hundred and sixty two (162) soil samples were collected at random at 0-20 cm, 20-40 cm and 40-60 cm soil depth from shea nut cake dumping sites in Jusonayilli, Gurugu and Kasalgu within the Sanaregu District of the Northern Region of Ghana, from September, 2010 to July, 2011. This is to isolate bacteria with high shea nut cake degrading ability and consequently select the potential application of these bacteria in bioremediation. The bacteria were grown in mineral salt medium supplemented with 2% shea nut cake as sole source of carbon. More Gram negative bacteria were involved in shea nut cake degradation than Gram positive bacteria. Two isolates which gave good growth on 5% shea nut cake agar were identified biochemically as Pseudomonas species. Both grew optimally at 35oC and at pH 7.0. Yeast extracts enhanced growth. Pseudomanas strain G9 degraded 71.25% shea nut cake, while Pseudomonas strain G38 degraded 50.35% shea nut cake within 48 h. Pseudomonas G9 can be used to degrade shea nut cake. G9 and G38 are different species of Pseudomonas and molecular typing such as PCR can be used to determine the exact spe-cies.Keywords: Shea nut cake, selective isolation, biodegradation, bacteria
... 1,2,4-Tricarboxybenzene representing the structural analogue of 4SPA is not oxidized because it, perhaps, also is not transported into the cell due to the possibly very narrow substrate specificity of the transport system for 4SPA or, perhaps, of the limited substrate specificity of the sulfophthalate dioxygenase. Consequently, there is no proof for the dioxygenation of this tricarboxy compound and, therefore, we cannot show the specific region of the dioxygenolytic attack onto 4SPA: positions 3,4-und 4,5-are accessible which then could yield the respective intermediary and unstable sulfodihydrodiols in analogy to both stable dihydrodiols known from the degradation of phthalate (Ribbons & Evans 1960;Eaton & Ribbons 1982). Therefore, we cannot completely exclude 3,4-dihydroxyphthalate from the pathway we have suggested in Figure 5. ...
Article
Full-text available
The bacteriumPseudomonas sp. strain RW31 isolated from the river Elbe utilized the ammonium salt of 4-sulfophthalate (4SPA) as sole source of carbon, sulfur, nitrogen, and energy and grew also with phthalate (PA) and several other aromatic compounds as sole carbon and energy source. The xenobiotic sulfo group of 4SPA was eliminated as sulfite, which transiently accumulated in the culture supernatant up to about 10 M and was slowly oxidized to the stoichiometrical amount of sulfate. Biodegradation routes of 4SPA as well as of PA converged into the protocatechuate pathway and from found activities for the decarboxylation of 4,5-dihydroxyphthalate we deduce this compound the first rearomaticized intermediate after initial dioxygenation. Protocatechuate then underwentmeta-cleavage mediated by a protocatechuate 4,5-dioxygenase activity which was competitively inhibited by the structurally related compound 3,4,5-trihydroxybenzoate; protocatechuate accumulated in the medium up to an about 2 mM concentration. Indications for the presence of selective transport systems are presented.
... Terephthalic acid has been designated by the U.S. Environmental Protection Agency as a pollutant (USEPA, 1978). Research on terephthalic acid degradation is also widespread concerned (Ribbons and Evans, 1960;Park et al., 2003;Crepaldi et al., 2002). ...
Article
The biodegradation of terephthalic acid (TA) by the Pseudomonas sp. was researched in this paper. The optimal nitrogen source was urea with its concentration of 1400 mg/l. The optimal conditions for TA degradation were optimized by orthogonal test. The test result showed the pH 7.0, temperature of 30°C and shaking speed of 140 rpm were the best condition for degradation. In that condition, terephthalic acid was almost degraded completely after 48 h cultivation of Pseudomonas sp. by inoculating 4% seed culture. Kinetics of degradation was performed at different initial TA concentrations. The degradation could be described with a first-order kinetics model. The half-life of degradation was about 12 h when the concentration of terephthalic acid was between 600 and 1000 mg/l.
... Mineralization of phthalic acid ester in the environment is largely microbial and involves a sequence of reactions that is common to all phthalates (Hashizume et al. 2002;Staples et al. 1997;Yuan et al. 2002). At first, the ester linkage between alkyl chains and the aromatic ring is hydrolyzed to form monoesters and then phthalic acid (Ribbons et al. 1984;Wang et al. 1999), which is oxidized via the 3-oxoadipate pathway (Engelhardt et al. 1976;Ribbons and Evans 1960). In the case of BBP, the same course of degradation, with monoesters as intermediates, was reported for different microorganisms Dutta 2003, 2008a;Xu et al. 2006). ...
Article
Full-text available
Butyl benzyl phthalate (BBP), an aryl alkyl ester of 1,2-benzene dicarboxylic acid, is extensively used in vinyl tiles and as a plasticizer in PVC in many commonly used products. BBP, which readily leaches from these products, is one of the most important environmental contaminants, and the increased awareness of its adverse effects on human health has led to a dramatic increase in research aimed at removing BBP from the environment via bioremediation. This review highlights recent progress in the degradation of BBP by pure and mixed bacterial cultures, fungi, and in sludge, sediment, and wastewater. Sonochemical degradation, a unique abiotic remediation technique, and photocatalytic degradation are also discussed. The degradation pathways for BBP are described, and future research directions are considered.
... The degradation of phthalic acid esters [1-5] and phthalic acid (O-phthalic acid) [6][7][8][9] has been studied extensively in various microorganisms. In a soil Pseudomonas and Pseudomonas testosteroni [7] 4,5-dihydroxyphthalic acid and protocatechuic acid were shown to be the intermediates in phthalic acid catabolism. ...
... All rights reserved. phthalic acid to the central intermediate, protocatechuate (Ribbons and Evans, 1960;Nomura et al., 1992). Due to their inherent aromaticity, however, phthalates accumulate in anoxic sediments and in these environments, less is known about their degradation. ...
Article
Phthalic acid esters (phthalates) are anthropogenic compounds that are used as plasticizers. Unfortunately, because phthalates are non‐covalently intercalated into plastic polymers they leach into the environment, accumulating in anoxic sediments. This has negative consequences for animal and human health. Denitrifying Betaproteobacteria, such as Aromatoleum aromaticum, can use ortho‐phthalate, derived by ester hydrolysis, as a carbon and energy source. Mergelsberg et al. (in press) deconstruct the pathway whereby ortho‐phthalic acid is converted, via the highly unstable phthaloyl‐CoA, to the central intermediate of anaerobic aromatic degradation, benzoyl‐CoA. The latter reaction is catalysed by UbiD‐like phthaloyl‐CoA decarboxylase (PCD). Succinyl‐CoA:o‐phthalate CoA‐transferase (SPT) generates phthaloyl‐CoA, which accumulates at only sub‐micromolar concentrations, while the Km of PCD for phthaloyl‐CoA is two‐orders of magnitude higher. This seemingly insurmountable kinetic barrier is overcome because A. aromatoleum massively over‐produces PCD and because the decarboxylation reaction is irreversible. These features of the pathway facilitate capture of phthaloyl‐CoA as it is released from SPT without the need for direct substrate‐channelling. The authors provide strong evidence from both in vivo and in vitro studies to support their conclusions. This work reveals how these anaerobic bacteria have rapidly evolved a stop‐gap measure to allow them to completely degrade an otherwise recalcitrant aromatic xenobiotic. This article is protected by copyright. All rights reserved.
... The dissimilatory pathway of phthalate was previously reported in a soil pseudomonad (11) that is probably different from P. testosteroni, as suggested by the operation of the orthocleavage pathway ofprotocatechuate. Although P. testosteroni degrades protocatechuate via the meta-cleavage pathway, it is evident from the present study that phthalate is also metabo (11) reported a manometric assay of 4,5-dihydroxyphthalate decarboxylase by measuring the decarboxylation under anaerobic conditions. ...
Article
A mutant strain of Pseudomonas testosteroni blocked in phthalate catabolism converted phthalate into 4,5-dihydroxyphthalate. The latter compound was isolated, and its physical properties were determined. A stoichiometric conversion of the compound to protocatechuate was demonstrated spectrophotometrically with crude extracts of a protocatechuate 4,5-dioxygenase-deficient mutant. Therefore, phthalate is metabolized through 4,5-dihydroxyphthalate and protocatechuate, which is further degraded by protocatechuate 4,5-dioxygenase in P. testosteroni. By using several mutants blocked in phthalate catabolism, 4,5-dihydroxyphthalate decarboxylase was shown to be induced by phthalate. A simple spectrophotometric assay for the enzyme is also reported.
... The aerobic biodegradation of PA, IPA and TPA has been studied since almost 60 years (Ribbons and Evans, 1960;Keyser et al., 1976), and has meanwhile been demonstrated in a large number of Grampositive and -negative bacteria, as well as in some fungi. For detailed lists of species that use the three phthalic acid isomers as sole source of carbon and energy we refer to previous reviews (Vamsee-Krishna and Phale, 2008;Gao and Wen, 2016). ...
Article
Full-text available
The environmentally relevant xenobiotic esters of phthalic acid (PA), isophthalic acid (IPA) and terephthalic acid (TPA) are produced on a million ton scale annually and are predominantly used as plastic polymers or plasticizers. Degradation by microorganisms is considered as the most effective means of their elimination from the environment and proceeds via hydrolysis to the corresponding phthalic acid isomers and alcohols under oxic and anoxic conditions. Further degradation of PA, IPA and TPA differs fundamentally between anaerobic and aerobic microorganisms. The latter introduce hydroxyl functionalities by dioxygenases to facilitate subsequent decarboxylation by either aromatizing dehydrogenases or cofactor‐free decarboxylases. In contrast, anaerobic bacteria activate the phthalic acids isomers to the respective thioesters using CoA ligases or CoA transferases followed by decarboxylation to the central intermediate benzoyl‐CoA. Decarboxylases acting on the three phthalic acid CoA thioesters belong to the UbiD enzyme family that harbor a prenylated FMN cofactor to achieve the mechanistically challenging decarboxylation. Capture of the extremely instable PA‐CoA intermediate is accomplished by a massive overproduction of PCD and a balanced production of PA‐CoA forming/decarboxylating enzymes. The strategy of anaerobic phthalate degradation probably represents a snapshot of an ongoing evolution of a xenobiotic degradation pathway via a short‐lived reaction intermediate. This article is protected by copyright. All rights reserved.
... The ease of phthalic acid biodegradation in nature follows the order: o-phthalate > terephthalate > isophthalate [7,24]. Aerobic bacteria use molecular oxygen as a cosubstrate to attack the stable aromatic ring of phthalate through dioxygenase-catalyzed addition of hydroxyl groups that facilitate decarboxylation to protocatechuate, a key intermediate of aerobic degradation of aromatic compounds [25][26][27][28][29]. Aerobic phthalate degradation has been studied in detail. ...
Article
Full-text available
Syntrophorhabdus aromaticivorans is a syntrophically fermenting bacterium that can degrade isophthalate (3- carboxybenzoate). It is a xenobiotic compound which has accumulated in the environment for more than 50 years due to its global industrial usage and can cause negative effects on the environment. Isophthalate degradation by the strictly anaerobic S. aromaticivorans was investigated to advance our understanding of the degradation of xenobiotics introduced into nature, and to identify enzymes that might have ecological significance for bioremediation. Differential proteome analysis of isophthalate- vs benzoate-grown cells revealed over 400 differentially expressed proteins of which only four were unique to isophthalate-grown cells. The isophthalate-induced proteins include a phenylacetate:CoA ligase, a UbiD-like decarboxylase, a UbiX-like flavin prenyltransferase, and a hypothetical protein. These proteins are encoded by genes forming a single gene cluster that putatively codes for anaerobic conversion of isophthalate to benzoyl-CoA. Subsequently, benzoyl-CoA is metabolized by the enzymes of the anaerobic benzoate degradation pathway that were identified in the proteomic analysis. In vitro enzyme assays with cell-free extracts of isophthalate-grown cells indicated that isophthalate is activated to isophthalyl-CoA by an ATP-dependent isophthalate:CoA ligase (IPCL), and subsequently decarboxylated to benzoyl-CoA by a UbiD family isophthalyl-CoA decarboxylase (IPCD) that requires a prenylated flavin mononucleotide (prFMN) cofactor supplied by UbiX to effect decarboxylation. Phylogenetic analysis revealed that IPCD is a novel member of the functionally diverse UbiD family (de)carboxylases. Homologs of the IPCD encoding genes are found in several other bacteria, such as aromatic compound-degrading denitrifiers, marine sulfate-reducers, and methanogenic communities in a terephthalate-degrading reactor. These results suggest that metabolic strategies adapted for degradation of isophthalate and other phthalate are conserved between microorganisms that are involved in the anaerobic degradation of environmentally relevant aromatic compounds.
... Phylogenetic analysis of 16S rRNA gene sequences shows that the isolated strains were positioned close with the members of genus Pseudomonas, which are previously reported to degrade persistent organic pollutants [45][46][47]. The 16S rRNA gene sequence of Pseudomonas sp. ...
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A Pseudomonas fluorescens strain SKP3 capable of utilizing both phthalic acid and terephthalic acid as sole source of carbon and energy was isolated by enrichment technique. Phthalic acid, terephthalic acid and protocatechuic acid were easily oxidized by both phthalate-grown and glucose-grown cells without a lag period. Phthalic acid is metabolized through the ortho cleavage pathway and terephthalic acid through the meta cleavage pathway and the enzymes of the two pathways are constitutive in nature. A large plasmid of approximately 140kb in size was found to be involved in the degradation of phthalates. The catabolic plasmid pSKL was transferable to different hosts.
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Different bacteria, isolated from soil by the enrichment method, were able to grow on phthalic acid as carbon source. Protocatechuate was identified as intermediate in phthalate metabolism. All phthalategrown bacteria oxidized phthalate and protocatechuate rapidly without having a lag-period. Benzoic acid, terephthalic acid, protocatechuic acid, salicylic acid, di- and mono-butyl phthalate were also metabolized by some of the organisms, benzoic acid being degraded via catechol and terephthalic acid via protocatechuate as intermediate. All organisms tested cleaved protocatechuate or catechol, respectively, by the ortho fission, when grown on phthalate, terephthalate, or benzoate as carbon source. A characterization and tentative identification of the organisms is given.
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The oxidation ofp-hydroxybenzoic acid, quinic acid, vanillin and coumarin in soil was studied. With vanillin, and particularly with coumarin, the lag phase for oxygen consumption was longer and the rate of oxygen consumption attained more than one peak. In soil preincubated with the relevant substrate, the second dose of the same substrate was oxidized more rapidly. If the soil was preincubated with glucose, the lag phase was also shortened and oxygen consumption was raised with all aromatic substrates.
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Aromatic compounds and steroids are among the remarkable variety of organic compounds utilized by rhodococci as growth substrates. This degradation helps maintain the global carbon cycle and has increasing applications ranging from the biodegradation of pollutants to the biocatalytic production of drugs and hormones. The catabolism of aromatic compounds and steroids converge as steroid degradation proceeds via aromatic intermediates. Consistent with the aerobic lifestyle of rhodococci, these pathways are rich in oxygenases. Analysis of five rhodococcal genomes confirms the modular nature of the aromatic compound catabolic pathways: peripheral pathways degrade compounds such as biphenyl and phthalate to common intermediates, while central pathways transform these intermediates, such as catechol and phenylacetate, to central metabolites. Studies of Rhodococcus jostii RHA1 in particular have revealed a similar modular structure of steroid degradation pathways, which is also conserved in related actinobacteria, such as Mycobacterium tuberculosis. Indeed, steroid degradation appears to be a very common, potentially ubiquitous characteristic of rhodococci. Nevertheless, the steroid catabolic pathways appear to be more redundant than the aromatic compound catabolic pathways. Finally, studies in rhodococci have helped elucidate the role of key steroid-degrading proteins including the Mce4 steroid uptake system which define a new class of ABC transporters. The significance of some of these recent discoveries for industrial processes and pathogenesis is discussed.
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Recent studies on the biodegradation phthalate esters in natural ecosystems, sewage, and laboratory cultures are reviewed. There is ample evidence to demonstrate that bacteria are major elements in the biodegradative processes and that in most situations complete oxidation of the aromatic ring occurs; much less is known about the catabolism of the alcoholic moiety, e.g., 2-ethylhexanol. Evidence is presented to support catabolic pathways in pseudomonads and micrococci that are initiated by successive hydrolyses of the diesters to give the phthalate anion. Thereafter a dioxygenase catalyzes the formation of 4,5-dihydro-4,5-dihydroxyphthalate, which is oxidized by an NAD-dependent dehydrogenase to give 4,5-dihydroxyphthalate, Protocatechuate, formed by decarboxylation of 4,5-dihydroxyphthalate, is the substrate for ring cleavage enzymes. Whereas flurorescent pseudomonads use the beta-ketoadipate pathway, the nonfluorescent strains and micrococci examined use of meta-cleavage (4,5-) route. All the intermediates proposed have been accumulated by enzymes purified from Pseudomonas fluorescens. Isophthalate and terephthalate (anions) are readily used as carbon sources by aerobic bacteria, and preliminary evidence is consistent with catabolic routes for these isomers converging at the ring-cleavage substrate protocatechuate. Some possible effects and interactions of synthetic organic chemicals with the natural microflora, and the influence of other vectors, is discussed in relation to the maintenance of the carbon cycle and environmental pollution.
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A Bacillus sp., isolated by anaerobic enrichment on a o-phthalic acid-nitrate medium, grew either aerobically or anaerobically on phthalic acid. Cells grown anaerobically on phthalate immediately oxidized phthalate and benzoate with nitrate, whereas aerobic oxidation only occurred after a lag period and was inhibited by chloramphenicol. 2-Fluoro-and 3-fluorobenzoate were formed from 3-fluorophthalate by cells grown anaerobically on phthalate. Aerobically grown cells immediately oxidized phthalate, benzoate, 3-hydroxybenzoate and gentisate with oxygen. The aerobic and anaerobic route of catabolism of phthalate may thus share an initial decarboxylation to benzoate. This is the first report of the anaerobic dissimilation of phthalic acid by a pure bacterial culture.
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Gram-positive Rhodococcus erythropolis strain S1 formed enzymes for the degradation of phthalate when grown in a phthalate-containing minimal medium. The membrane fraction prepared from phthalate-grown cells by ultrasonication converted phthalate to protocatechuate as the final product. Using two membrane-bound enzymes, phthalate 3,4-dioxygenase (PO) and 3,4-dihydro-3,4-dihydroxyphthalate 3,4-dehydrogenase (PH), prepared by solubilization of the membrane fraction, 3,4-dihydroxyphthalate was selectively obtained from phthalata. Fe2+ and Mn2+ stimulated the formation of 3,4-dihydroxyphthalate by the membrane-bound PO and PH system.
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The primary and ultimate biodegradability of phthalic acid, monobutyl phthalate, and five structurally diverse phthalic acid ester plasticizers in river water and activated sludge samples were determined via ultraviolet spectrophotometry, gas chromatography, and CO2 evolution. The compounds studied underwent rapid primary biodegradation in both unacclimated river water and acclimated activated sludge. When activated sludge acclimated to phthalic acid esters was used as the inoculum for the CO2 evolution procedure, greater than 85% of the total theoretical CO2 was evolved. These studies demonstrate that the phthalic acid ester plasticizers and intermediate degradation products readily undergo ultimate degradation in different mixed microbial systems at concentrations ranging from 1 to 83 mg/liter.
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Phthalate ester isomers, including dimethyl phthalate (DMP), dimethyl isophthalate (DMI) and dimethyl terephthalate (DMT), were found to be transformed by Rhodococcus rubber Sa isolated from a mangrove sediment using DMT as a carbon source initially. At a concentration of 80 mg l−1, transformation of DMP, DMI and DMT was achieved in 9, 1 and 5 days, respectively. During the hydrolytical transformation of DMP, DMI and DMT, their corresponding intermediates were identified as mono-methyl phthalate (MMP), mono-methyl isophthalate (MMI) and mono-methyl terephthalate (MMT), suggesting that transformation of all three isomers followed an identical biochemical pathway of de-esterification. However, none of the produced monoesters was further transformed by R. rubber Sa and they accumulated in the culture media during incubation. It seems that further transformation of monoesters require a set of hydrolytic enzymes different from those involved in the first transformation reaction. Kinetics of DMT, DMI and DMP transformation was well described by the modified Gompertz model independent of the individual substrate condition or a mixture of the three isomers. Both DMI and DMT were easier transformed substrates than DMP, resulting in higher maximum transformation rate (Rm) and shorter lag time phase (λ) derived from the modified Gompertz model. The modified Gompertz model based on one-substrate system can be used in fitting transformation kinetics of mixture substrate system. Our data suggest that degradation of phthalate diesters involves different enzymes in the hydrolysis of the two identical ester groups.
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A dibutyl phthalate (DBP) transforming bacterium, strain M673, was isolated and identified as Acinetobacter sp. This strain could not grow on dialkyl phthalates, including dimethyl, diethyl, dipropyl, dibutyl, dipentyl, dihexyl, di(2-ethylhexyl), di-n-octyl, and dinonyl phthalate, but suspensions of cells could transform these compounds to phthalate via corresponding monoalkyl phthalates. During growth in Luria-Bertani medium, M673 produced the high amounts of non-DBP-induced intracellular hydrolase in the stationary phase. One DBP hydrolase gene containing an open reading frame of 1,095 bp was screened from a genomic library, and its expression product hydrolyzed various dialkyl phthalates to the corresponding monoalkyl phthalates.
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In order to investigate phthalates in landfill leachates, four landfill simulation reactors, filled with municipal solid waste from a housing area, were studied. Plasticised polyvinyl chloride (PVC) was added to two of the reactors. Two reactors, one with and one without the additional PVC, were aerated for 3 months to achieve methanogenic conditions. The other two became acidogenic a few days after filling and closing. After approximately 3 years, the acidogenic waste became methanogenic. The leachates were analysed for phthalic acid diesters and their degradation products, phthalic acid monoesters and o-phthalic acid. The occurrence of monobenzyl phthalate (MbenzP) and mono(2-ethylhexyl) phthalate (MEHP) showed that the diesters, butylbenzyl phthalate (BBP) and di(2-ethylhexyl) phthalate (DEHP), released from the PVC products had been transformed, and that they were not completely sorbed to particles or to the waste material. Monoesters were observed once methanogenic conditions were established. The monoesters and phthalic acid were present in concentrations several orders of magnitude higher than the diesters themselves. Our results show that it is important to include monoesters in studies of the fate of diesters. To date, monoesters have been neglected in investigations of organic pollutants in landfill leachates.
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Methods of aerobic degradation of aromatic compounds in the biosphere are well understood, but it is only relatively recently that it has been shown how some bacteria can also degrade these substrates in the absence of molecular oxygen. This occurs by photometabolism (Athiorhodaceae), nitrate respiration (Pseudomonas and Moraxella sp.) and methanogenic fermentation (a consortium) in which the benzene nucleus is first reduced and then cleaved by hydrolysis to yield aliphatic acids for cell growth. These methods may be used by microbial communities to catabolise man-made pollutants.
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Trace metal speciation in aquatic environments is inherently complex due to the large number of possible interactions with dissolved and particulate components. Adsorption onto iron oxyhydroxide and bacterial surfaces, as well as the formation of metal-ligand complexes can play important roles in controlling the fate and transport of trace metals in natural environments. The objective of this study is to describe and understand metal speciation and distribution in a complex biogeochemical system by incrementally increasing the complexity from simple binary systems to a dynamic quaternary system containing a trace metal, iron oxide and bacteria that are active and metabolizing an organic ligand. Copper, cadmium, and phthalic acid (H2Lp) adsorption onto ferrihydrite in binary systems was well reproduced using the diffuse layer model (DLM). The adsorption of H2Lp adsorption was analogous to that of inorganic diprotic acids in terms of the relationship between the adsorption constants and acidity constants. In ternary systems H2Lp caused Cu2+ or Cd2+ adsorption to be either enhanced (due to surface ternary complex formation) or inhibited (due to solution complex formation) depending on the conditions. The DLM could only describe the effect of H2Lp on metal ion sorption by including ternary complexes of the form ≡FeOHMLp (0), where ≡FeOH is a surface site and M is Cu or Cd. The relationship between binary metal adsorption constants and the ternary complex adsorption constants from this and previous studies suggest several properties of ternary complexes. First, ternary complex structures on both ferrihydrite and goethite are either the same or similar. Second, those cations having large adsorption constants also have large equilibrium constants for ternary complex formation. Third, ligands forming stronger solution complexes with cations will also form stronger surface ternary complexes but because of the strong solution complexes these ligands will not necessarily enhance cation adsorption. The bacterial strain Comamonas spp. was isolated from the activated sludge of a wastewater treatment plant. Comamonas spp. could effectively degrade H2Lp in the presence of Cd2+ and ferrihydrite and was therefore chosen to study the effect of H2Lp degradation on Cd2+ speciation. Proton, cadmium and H2Lp adsorption onto Comamonas spp. were measured. The Comamonas spp. titration curve is flatter than that of ferrihydrite, indicating a higher degree of site heterogeneity at the bacterial surface. Adsorption edges of Cd2+ adsorption onto Comamonas spp. occurred over about 4~5 pH units compared to those of ferrihydrite which occurred over ≈ 2 pH units on a dry weight basis. Comamonas spp. can accumulate a larger amount of Cd2+ than ferrihydrite especially under lower pH conditions. Proton and Cd2+ adsorption onto Comamonas spp. cells over a wide sorbent/sorbate and pH range was reasonably well described by a four site non-electrostatic model. The acid-base and Cd2+ adsorption behaviour of Comamonas spp. in this work were within the range of studies of bacteria adsorption. Phthalic acid adsorption onto inactive Comamonas spp. was negligible over a pH range of 3 to 8 and became significant only at pH < 3 where H2Lp was fully protonated. This is consistent with the proposed mechanism for ligand adsorption onto bacterial surfaces which involved a balance between hydrophobic interaction and electrostatic repulsion. The presence of H2Lp decreased Cd2+ adsorption onto Comamonas spp. due to competition for Cd2+ between the bacterial cell surface and the formation of solution complexes of Cd2+. This was accurately modelled with the Cd-Lp solution species indicating that no significant surface ternary interaction occurred between Cd2+, phthalic acid and Comamonas spp.. Cadmium adsorption onto ferrihydrite-Comamonas spp. mixtures was slightly less than the simple additive predicted adsorption of ferrihydrite plus Comamonas spp.. This suggests there is a weak interaction between ferrihydrite and Comamonas spp. and this interaction could be modelled by including a generic reaction between the ferrihydrite and Comamonas spp. surface sites. Cadmium distribution in a system of inactive Comamonas spp.-ferrihydrite in the absence and presence of H2Lp could be predicted by combining the ferrihydrite and bacteria models with the inclusion of the ferrihydrite-bacteria interaction. The effects of H2Lp degradation on Cd2+ distribution were investigated in dynamic systems with live bacteria. Results showed that Cd2+ adsorption in these dynamic systems was reasonably estimated with the model parameters developed in the proceeding experiments though uncertainty exists in the dynamic process with regards to H2Lp biodegradation products and changes in the bacteria population. This thesis was therefore able to provide a better understanding of metal speciation in complex and heterogeneous realistic environments by experimentally examining and modelling metal speciation and distribution in various systems with increasing complexity. This helps to bridge the gap of quantitative description of metal speciation from simple laboratory experiment systems to real world systems, both natural and engineered.
Article
4,5-Dihydroxyphthalate (DHP) production was carried out using Pseudomonas testosteroni immobilized in alginate gel beads. Strontium chloride was more suitable for a gelation agent with regard to DHP production than calcium chloride or barium chloride. The optimal gelation time was about 0.5 h, and the DHP production rate decreased with an increase in gelation time. The optimal pH for DHP production using the immobilized cells was shifted about 1.0 to the alkali side compared with that for the suspended cells. A repeated batch operation using the immobilized cells was carried out. It was effective for efficient DHP production, and a high production rate was maintained to the fifth cycle.
Article
Phthalate oxygenase was induced in Rhodococcus erythropolis S-1, a Gram-positive bacterium, when this bacterium was cultured in a medium containing phthalate as a sole carbon source. The enzyme was purified 118-fold with 4.7% activity yield. The purified enzyme appeared homogenous on native PAGE. This enzyme is a large protein (213 kDa), a tetramer of identical 56kDa monomers, and a flavoprotein containing FAD with NADH-dependent dioxygenase activity. The enzyme is specific for phthalate and other closely related aromatic compounds. Optimum pH and temperature were 6.5 and 40°C. The Km for phthalate and NADH were 0.040 mM and 0.069 mM. The enzyme catalyzes dihydroxylation of phthalate to form 3,4-dihydro-3,4-dihydroxyphthalate with consumption of NADH and oxygen.
Article
The ability of strain Rhodococcus opacus 1CP to utilize 3-hydroxybenzoate (3-HBA) and gentisate in concentrations up to 600 and 700 mg/L, respectively, as sole carbon and energy sources in liquid mineral media was demonstrated. Using high-performance liquid chromatography (HPLC) and thin-layer chromatography, 2,5-dihydroxybenzoate (gentisate) was identified as the key intermediate of 3-hydroxybenzoate transformation. In the cell-free extracts of the strain grown on 3-HBA or gentisate, the activities of 3-hydroxybenzoate 6-hydroxylase, gentisate 1,2-dioxygenase, and maleylpyruvate isomerase were detected. During growth on 3-HBA, low activity of catechol 1,2-dioxygenase was detected. Based on the data obtained, the pathway of 3-HBA metabolism by strain R. opacus 1CP was proposed.
Article
Phthalates are common plasticizers used in pPVC (plasticized polyvinyl chloride) products. Phthalates are commonly found in the child rearing products (for teething, toys etc.). blood bags, dialysis tubing, paints, lacquers, cosmetics, coatings of capsules etc. The present study was conducted to explore the potential of new microbial strains for the biodegradation and biotransformation of phthalic acid. A bacterial isolate, Pseudomonas sp. P1, was found to degrade phthalic acid in agar plate assay as evident by the formation of clear zone around the colony. The strain was tested for the growth and tolerance limit on different concentrations (10-3000 ppm) of phthalic acid in mineral salt medium with and without glucose. On mineral salt agar plates, containing phthalic acid as a sole source of carbon, rich growth along with the hydrolyzing zone was observed upto the maximum concentration of 2800 ppm without glucose and upto the maximum concentration of 2900 ppm of phthalic acid with glucose. Transformational studies were carried out in mineral salt liquid medium containing varying concentrations (100-500 ppm) of phthalic acid. Microbial growth was checked at 570 nm at different time intervals and the cell free supernatant was analyzed for the disappearance of phthalic acid at 280 nm. The highest percentage of degradation of phthalic acid was found at 37°C and pH 8, i.e. 59% and 64% respectively. In mineral salt medium without glucose, phthalic acid degraded up to 72% at 500 ppm after 48 hours of incubation.
Article
ortho‐Phthalate derives from industrially produced phthalate esters which are massively used as plasticizers and constitute major emerging environmental pollutants. The pht pathway for the anaerobic bacterial biodegradation of o‐phthalate involves its activation to phthaloyl‐CoA followed by decarboxylation to benzoyl‐CoA. Here we have explored further the pht peripheral pathway in denitrifying bacteria and shown that it requires also an active transport system for o‐phthalate uptake that belongs to the poorly characterized class of TAXI‐TRAP transporters. The construction of a fully functional pht cassette combining both catabolic and transport genes allowed to expand the o‐phthalate degradation ecological trait to heterologous hosts. Unexpectedly, the pht cassette also allowed the aerobic conversion of o‐phthalate to benzoyl‐CoA when coupled to a functional box central pathway. Hence, the pht pathway may constitute an evolutionary acquisition for o‐phthalate degradation by bacteria that thrive either in anoxic environments, or in environments that face oxygen limitations and that rely on benzoyl‐CoA, rather than on catecholic central intermediates, for the aerobic catabolism of aromatic compounds. Finally, the recombinant pht cassette was used both to screen for functional aerobic box pathways in bacteria, and to engineer recombinant biocatalysts for o‐phthalate bioconversion into sustainable bioplastics, e.g., polyhydroxybutyrate, in plastic recycling industrial processes. This article is protected by copyright. All rights reserved.
Chapter
Die festen anorganischen Bestandteile des Bodens sind Minerale. Sie lassen sich unterteilen in primäre und sekundäre Minerale. Unter primären Mineralen sollen im folgenden alle solche verstanden werden, die magmatischen oder metamorphen Ursprungs sind, während zu den sekundären Mineralen alle bei der Verwitterung entstandenen Minerale gezählt werden sollen, gleichgültig ob sie direkt bei der Verwitterung magmatischer oder metamorpher Gesteine oder auf dem Umweg über das Sediment in den Boden gelangten. Tonminerale des Bodens, die dem Sedimentgestein entstammen, sind daher in gleicher Weise sekundär wie solche, die sich bei der Verwitterung magmatischer Gesteine zum Boden bildeten.
Chapter
A large variety of naturally occurring and man-made compounds pose the danger of thyroid disease by interfering with thyroid function. These compounds can alter thyroid structure and function by acting directly on the gland or by affecting its regulatory mechanisms. The gland may increase in size to become a goiter. Thyroid hormone secretion may remain adequate or become insufficient, depending on dietary iodine intake or the presence of underlying thyroid disease.
Article
A strain PA-18 was isolated from the active sludge of p-phthalic acid (PTA) wastewater treatment in Yangtze Petrochemical Company. The 16SrDNA fragment was amplified from strain PA-18 by PCR, and the 16SrDNA sequence analysis indicated that strain PA-18 shared 99% 16SrDNA sequence homology with Pseudomonas sp. In the phylogenetic framework of bacterial classification, PA-18 belongs to Pseudomonas sp. Under the condition of temperature 37°C, pH 7.0 and OD660nm 2.0, the PTA decomposition rate of this bacterial strain was beyond 95% after 24 h. Meanwhile, this strain also could treat PTA wastewater with CODCr removal of 85%. p-Phthalic acid was degraded by the strain PA-18 through the intermediate formation of protocatechuic acid in the aerobic state.
Article
This chapter discusses the evaluation of methods used to determine metabolic pathways. It also discusses the methods used to investigate the main metabolic pathways found in microorganisms. Two distinguishing features of the chemistry of living matter have called for the development of specialized experimental approaches and methods—namely, the extreme rapidity by which reactions of the metabolic network are catalyzed, and by the means by which the regulation of their rates is accomplished. The configuration of an enzyme, and the efficiency of its catalytic centre, may be profoundly altered when metabolites other than substrates or products are bound to the protein molecule. This recognition of allosteric behavior permits a description of mechanisms by which many metabolic pathways may be regulated. The chapter explains the way in which the studies of metabolic pathways in mammals may resemble or differ from those concerned with microbes. With organisms of both kinds, some limited information can be obtained by relating the compounds excreted by the organism to those supplied in its diet. The chapter illustrates two themes for explaining the use of induced auxotrophs in determining biosynthetic. The first is that the complexities of metabolism require experimental findings to be interpreted with caution; and second, that the elucidation of biosynthetic pathways proceeds from an outline of the steps involved, through a more detailed knowledge of their chemistry, to a study of isolated enzymes and the nature of their regulation in the cell.
Article
Phthalates or phthalic acid esters are a group of xenobiotic and hazardous compounds blended in plastics to enhance their plasticity and versatility. Enormous quantities of phthalates are produced globally for the production of plastic goods, whose disposal and leaching out into the surroundings cause serious concerns to the environment, biota and human health. Though in silico computational, in vitro mechanistic, pre-clinical animal and clinical human studies showed endocrine disruption, hepatotoxic, teratogenic and carcinogenic properties, usage of phthalates continues due to their cuteness, attractive chemical properties, low production cost and lack of suitable alternatives. Studies revealed that microbes isolated from phthalate-contaminated environmental niches efficiently bioremediate various phthalates. Based upon this background, this review addresses the enumeration of major phthalates used in industry, routes of environmental contamination, evidences for health hazards, routes for in situ and ex situ microbial degradation, bacterial pathways involved in the degradation, major enzymes involved in the degradation process, half-lives of phthalates in environments, etc. Briefly, this handy module would enable the readers, environmentalists and policy makers to understand the impact of phthalates on the environment and the biota, coupled with the concerted microbial efforts to alleviate the burden of ever increasing load posed by phthalates.
Article
Phthalates or phthalic acid esters are a group of xenobiotic and hazardous compounds blended in plastics to enhance their plasticity and versatility. Enormous quantities of phthalates are produced globally for the production of plastic goods, whose disposal and leaching out into the surroundings cause serious concerns to the environment, biota and human health. Though in silico computational, in vitro mechanistic, pre-clinical animal and clinical human studies showed endocrine disruption, hepatotoxic, teratogenic and carcinogenic properties, usage of phthalates continues due to their cuteness, attractive chemical properties, low production cost and lack of suitable alternatives. Studies revealed that microbes isolated from phthalate-contaminated environmental niches efficiently bioremediate various phthalates. Based upon this background, this review addresses the enumeration of major phthalates used in industry, routes of environmental contamination, evidences for health hazards, routes for in situ and ex situ microbial degradation, bacterial pathways involved in the degradation, major enzymes involved in the degradation process, half-lives of phthalates in environments, etc. Briefly, this handy module would enable the readers, environmentalists and policy makers to understand the impact of phthalates on the environment and the biota, coupled with the concerted microbial efforts to alleviate the burden of ever increasing load posed by phthalates.
Article
Fluorochemicals are rare in Nature and fluoroaromatic compounds have not been described as natural products with respect to formation of aryl-fluorine bonds. By contrast many synthetic fluoroaromatic compounds are substrates for several microbial enzymes, particularly oxygenases, and are transformed to previously undescribed fluorochemicals suitable for further modifications by other enzymes systems or by chemical means. These lead to interesting multi-functional molecules, monomers for novel chiral and achiral polymers, chiral intermediates and synthons for some heterocycles and α- amino acids. Wild-type and mutant microbial strains have been used to biotransform some fluoroaromatic compounds in near quantitative yields to novel fluorinated products, as well as other flourophenolics already known by chemical synthesis. Some of the microbial transformations of mono-, di-, tri- and tetrafluoroaromatic compounds are described, and the vast potential of further biotransformations is indicated.
Article
The fungusAspergillus niger degraded homophthalic acid through the involvement ofo-hydroxyphenylacetic acid and homogentisic acid as the metabolic intermediates. Isolation of intermediates was carried out by extracting the spent medium and by using inhibitor in replacement culture techniques. Metabolites were characterized by various physicochemical methods. Oxygen uptake studies and enzyme investigations also confirmed that the degradation of homophthalic acid follows through these intermediates in the fungus.
Article
produces inducibly a hydro-lyase which catalyzes the reversible conversion of γ=oxalomesaconate into (−)-γ-oxalocitramalate. The enzyme has been purified to homogeneity from the bacteria grown with phthalate. The enzyme was a dimeric protein (pI=4.9) with a Mr of 68,000 and showed a high specificity for γ-oxalomesaconate (Km=14 μM) and (−)-γ-oxalocitramalate (Km=6.4 μM). Equilibrium constant for the hydration of γ-oxalomesaconate at pH 8.0 and 24°C was 2.5. Various thiols activated the enzyme.
Article
acid, whichreducedthegasproduction and enhanced thebuildup ofintermediates. Useofhigh-performance liquid chromatography andtwogas chromatographic procedures yielded identification ofthefollowing compounds: caffeate, p-hydroxycinnamate, cinnamate, phenylpropionate, phenylacetate, benzoate, andtoluene during ferulate degradation; andbenzene, cyclohexane, methylcyclohexane, cyclohexanecarboxylate, cyclohexanone, 1-methylcyclohexanone, pimelate, adipate, succinate, lactate, heptanoate, caproate, isocaproate, valerate, butyrate, isobutyrate, propionate, and acetate during thedegradation ofeither benzoate or ferulate. Basedon theidentification oftheabove compounds, more complete reductive pathways forferulate andbenzoate areproposed. Benzoate hasbeenusedasthemodelcompound fora numberofstudies ontheanaerobic degradation ofaromatic compounds. Methanogenic benzoate degradation wasstud- iedbyseveral different laboratories (2,9,17,19,24),and pathways forring reduction andfission weredescribed. The information wasreviewed andthepathways weresumma- rized byEvans(7). Morecomplex aromatic substrates have alsobeeninvestigated. Methanogenic fermentation of phenylpropionate andphenylacetate wasexamined byBalba andEvans(3), andafewrelated aromatic compounds were considered during theinvestigations onbenzoate (6,26). Kaiser andHanselmann (16) studied theanaerobic degrada- tion ofmethoxyl andhydroxyl trisubstituted benzenoids by methanogenic consortia enriched fromfreshwater anaerobic sediments. Bryantandco-workers (S.BarikandM.P. Bryant, Abstr. Annu.Meet.Am.Soc.Microbiol. 1984, 172, p.133)investigated thedegradation ofbenzoate, phenylace- tate, andphenolbymethanogenic enrichments andby syntrophic associations ofhydrogen-producing andhydro-
Article
Biotransformations of 3-fluorophthalic acid have been investigated using blocked mutants of Pseudomonas testosteroni that are defective in the metabolism of phthalic acid (benzene-1,2-dicar-boxyfic acid). Mutant strains were grown with L-glutamic acid in the presence of 3-fluorophthalic acid as inducer of phthalic acid catabolic enzymes. Products that accumulated in the medium were isolated, purified and identified as the fluoroanalogues of those produced from phthalic acid by the same strains. The previously undescribed fluorochemicals cis-3-fluoro-4,5-dihydro-4,5-dihydroxyphthalic acid (VI) and 3-fluoro-4,5-dihydroxyphthalic acid (VII) have been obtained by biotransformation of 3-fluorophthalic acid, and 3-fluoro-5-hydroxyphthalic acid (X) from (VI) by freeze drying. In addition, samples of 2-fluoro-3,4-dihydroxybenzoic acid (2-fluoroprotocatechuic acid, VIII) and 3-fluoro-4,Sdi-hydroxybenzoic acid (5-fluoroprotocatechuic acid, IX) were obtained with a mutant deficient in the ring-fission enzyme, showing that the fluorine substituent in their precursor substrate (VII) is not recognized by the decarboxylase of the pathway, which shows no preference for which carboxyl group is removed. These studies of 3-fluorophthalic acid catabolism demonstrate the opportunities available for the production of novel fluorochemicals in reasonable yields by microbial transformations.
Article
Moraxella sp. isolated from soil grows anaerobically on benzoate by nitrate respiration; nitrate or nitrite are obligatory electron acceptors, being reduced to molecular N2 during the catabolism of the substrate. This bacterium also grows aerobically on benzoate. 2. Aerobically, benzoate is metabolized by ortho cleavage of catechol followed by the beta-oxoadipate pathway. 3. Cells of Moraxella grown anaerobically on benzoate are devoid of ortho and meta cleavage enzymes; cyclohexanecarboxylate and 2-hydroxycyclohexanecarboxylate were detected in the anaerobic culture fluid. 4. [ring-U-14C]Benzoate, incubated anaerobically with cells in nitrate-phosphate buffer, gave rise to labelled 2-hydroxycyclohexanecarboxylate and adipate. When [carboxy-14C]benzoate was used, 2-hydroxycyclohexanecarboxylate was radioactive but the adipate was not labelled. A decarboxylation reaction intervenes at some stage between these two metabolites. 5. The anaerobic metabolism of benzoate by Moraxella sp. through nitrate respiration takes place by the reductive pathway (Dutton & Evans, 1969). Hydrogenation of the aromatic ring probably occurs via cyclohexa-2,5-dienecarboxylate and cyclohex-1-enecarboxylate to give cyclohexanecarboxylate. The biochemistry of this reductive process remains unclear. 6. CoA thiol esterification of cyclohexanecarboxylate followed by beta-oxidation via the unsaturated and hydroxy esters, would afford 2-oxocyclohexanecarboxylate. Subsequent events in the Moraxella culture differ from those occurring with Rhodopseudomonas palustris; decarboxylation precedes hydrolytic cleavage of the alicyclic ring to produce adipate in the former, whereas in the latter the keto ester undergoes direct hydrolytic fission to pimelate.
Article
Full-text available
Thesis (Ph. D. in Biochemistry)--University of California, Berkeley, Jan. 1957. Includes bibliographical references (leaves 52-54).
Article
Full-text available
N-Formylmaleamic acid, a probable intermediate in the bacterial metabolism of nicotinic acid, has been synthesized by photoisomerization of its trans isomer, N-formylfumaramic acid. The compound previously reported to be N-formylmaleamic acid has been shown to be N-formylfumaramic acid.
Article
Data are presented indicating that the major pathway for the oxidation of naphthalene by a strain of Pseudomonas occurs via salicylic acid, which is further oxidized through catechol to β-ketoadipic acid. On the basis of growth, simultaneous adaptation, and cell-free extract experiments, the following compounds are regarded as unlikely intermediates in naphthalene dissimilation: 1,4-naphthoquinone, α-naphthol, β-naphthol, 1,3-dihydroxynaphthalene, 2,3-dihydroxynaphthalene, 1,5-dihydroxynaphthaIene, phenol, trans-o-hydroxycinnamic acid, and phthalic acid. Evidence was found that a second pathway of naphthalene oxidation produces 1,2-naphthoquinone. 1,2-Dihydroxynaphthalene was found to be non-enzymatically converted to 1,2-naphthoquinone. The 1,2-naphthoquinone was not further metabolized and was found to be responsible for the characteristic brown to reddish orange color of the culture medium. Omission of FeCl2 and MgSO4 from the basal medium prevented the formation of salicylic acid but did not interfere with the production of 1,2-naphthoquinone.
The enzymes which catalyze reactions of molecular oxygen occur in three principle classes: (i) oxygen transferases, (ii) mixed function oxidases, and (iii) electron transferases. The first class catalyzes the transfer of a molecule of molecular oxygen to substrate. The second class catalyzes the transfer of one atom of the oxygen to substrate; the other atom undergoes two-equivalent reduction. The third class catalyses the reduction of molecular oxygen to hydrogen peroxide or to water.
Article
A cell-free bacterial preparation is described which can oxidatively cleave gentisic acid to yield maleylpyruvic acid. In the presence of GSH this preparation can be made to catalyze the isomerization and hydrolysis of maleylpyruvate to yield fumaric and pyruvic acids. Other sulfhydryl-containing compounds cannot replace reduced glutathione.
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