Ability of Activated Sludge to Degrade Nitrobenzene in Municipal Wastewater

Pseudomonas pseudoalcaligenes JS45 utilizes nitrobenzene as the sole source of nitrogen, carbon, and energy. Previous studies have shown that degradation of nitrobenzene involves the reduction of nitrobenzene to nitrosobenzene and hydroxylaminobenzene, followed by rearrangement to 2-aminophenol, which then undergoes meta ring cleavage to 2-aminomuconic semialdehyde. In the present paper, we report the enzymatic reactions responsible for the release of ammonia after ring cleavage. 2-Aminomuconic semialdehyde was oxidized to 2aminomuconate in the presence of NAD by enzymes in crude extracts. 2-Aminomuconate was subsequently deaminated stoichiometrically to 4-oxalocrotonic acid. No cofactors are required for the deamination. Two enzymes, 2-aminomuconic semialdehyde dehydrogenase and a novel 2-aminomuconate deaminase, distinguished by partial purification of the crude extracts, catalyzed the two reactions. 4-Oxalocrotonic acid was further degraded to pyruvate and acetaldehyde. The key enzyme, 2-aminomuconate deaminase, catalyzed the hydrolytic deamination that released ammonia, which served as the nitrogen source for growth of the organism.

mentioning

confidence: 99%

Studies of the catabolic pathway of degradation of nitrobenzene by Pseudomonas pseudoalcaligenes JS45: removal of the amino group from 2-aminomuconic semialdehyde

He¹,

Spain²

1997

“…The pollution potential is great, and nitrobenzene is listed as a U.S. Environmental Protection Agency priority pollutant (17), yet little is known about its biodegradation. Degradation of nitrobenzene has been detected in various waste streams and sludges (9,25,26) and in soil enrichment cultures (13,21), but the degradative pathways remain unknown.…”

mentioning

confidence: 99%

Degradation of nitrobenzene by a Pseudomonas pseudoalcaligenes

Nishino¹,

Spain²

1993

241

132

A Pseudomonas pseudoalkaligenes able to use nitrobenzene as the sole source of carbon, nitrogen, and energy was isolated from soil and groundwater contaminated with nitrobenzene. The range of aromatic substrates able to support growth was limited to nitrobenzene, hydroxylaminobenzene, and 2-aminophenol. Washed suspensions of nitrobenzene-grown cells removed nitrobenzene from culture fluids with the concomitant release of ammonia. Nitrobenzene, nitrosobenzene, hydroxylaminobenzene, and 2-aminophenol stimulated oxygen uptake in resting cells and in extracts of nitrobenzene-grown cells. Under aerobic and anaerobic conditions, crude extracts converted nitrobenzene to 2-aminophenol with oxidation of 2 mol of NADPH. Ring cleavage, which required ferrous iron, produced a transient yellow product with a maximum A380. In the presence of NAD, the product disappeared and NADH was produced. In the absence of NAD, the ring fission product was spontaneously converted to picolinic acid, which was not further metabolized. These results indicate that the

“…Bacteria that metabolize polar nitroaromatic compounds such as the mononitrobenzoates (3,17), mononitrophenols (33,40), and several of the dinitrophenol isomers (2, 14) have been described, but little is known about the degradation of nonpolar nitroaromatic compounds. Biodegradation of nitrobenzene has been reported in activated sludge (26,28), in municipal wastewater systems (9), in aniline plant wastewater (26), and in nitrobenzene plant wastewater (27). In one study, sewage effluent converted nitrobenzene to aniline under anaerobic conditions, but under aerobic conditions nitrobenzene disappeared and no aromatic amines were detected (12).…”

mentioning

confidence: 99%

Biotransformation of nitrobenzene by bacteria containing toluene degradative pathways

Haigler

Spain

1991

108

Nonpolar nitroaromatic compounds have been considered resistant to attack by oxygenases because of the electron withdrawing properties of the nitro group. We have investigated the ability of seven bacterial strains containing toluene degradative pathways to oxidize nitrobenzene. Cultures were induced with toluene vapor prior to incubation with nitrobenzene, and products were identified by high-performance liquid chromatography and gas chromatography-mass spectrometry. Pseudomonas cepacia G4 and a strain of Pseudomonas harboring the TOL plasmid (pTN2) did not transform nitrobenzene. Cells of Pseudomonas putida Fl and Pseudomonas sp. strain JS150 converted nitrobenzene to 3-nitrocatechol. Transformation of nitrobenzene in the presence of 1802 indicated that the reaction in JS150 involved the incorporation of both atoms of oxygen in the 3-nitrocatechol, which suggests a dioxygenase mechanism. P. putida 39/D, a mutant strain of P. putida Fl, converted nitrobenzene to a compound tentatively identified as cis-1,2-dihydroxy-3-nitrocyclohexa-3,5diene. This compound was rapidly converted to 3-nitrocatechol by cells of strain JS150. Cultures of Pseudomonas mendocina KR-1 converted nitrobenzene to a mixture of 3and 4-nitrophenol (10 and 63%, respectively). Pseudomonas pickettii PKO1 converted nitrobenzene to 3-and 4-nitrocatechol via 3-and 4-nitrophenol. The nitrocatechols were slowly degraded to unidentified metabolites. Nitrobenzene did not serve as an inducer for the enzymes that catalyzed its oxidation. These results indicate that the nitrobenzene ring is subject to initial attack by both mono-and dioxygenase enzymes.