Evaluation of 4-bromophenol biodegradation in mixed pollutants system by Arthrobacter chlorophenolicus A6 in an upflow packed bed reactor

Bromophenol is listed as priority pollutant by U.S. EPA, however, there is no report so far on its removal in mixed pollutants system by any biological reactor operated in continuous mode. Furthermore, bromophenol along with chlorophenol and nitrophenol are usually the major constituents of paper pulp and pesticide industrial effluent. The present study investigated simultaneous biodegradation of these three pollutants with specially emphasis on substrate competition and crossed inhibition by Arthrobacter chlorophenolicus A6 in an upflow packed bed reactor (UPBR). A 2³ full factorial design was employed with these pollutants at two different levels by varying their influent concentration in the range of 250–450 mg l^?1. Almost complete removal of all these pollutants and 97 % effluent toxicity removal were achieved in the UPBR at a pollutant loading rate of 1707 mg l^?1 day^?1 or lesser. However, at higher loading rates, the reactor performance deteriorated due to transient accumulation of toxic intermediates. Statistical analysis of the results revealed a strong negative interaction of 4-CP on 4-NP biodegradation. On the other hand, interaction effect between 4-CP and 4-BP was found to be insignificant. Among these three pollutants 4-NP preferentially degraded, however, 4-CP exerted more inhibitory effect on 4-NP biodegradation. This study demonstrated the potential of A. chlorophenolicus A6 for biodegradation of 4-BP in mixed pollutants system by a flow through UPBR system.     

Biodegradation of direct blue 129 diazo dye by Spirodela polyrrhiza: An artificial neural networks modeling

Phytoremediation potential of the aquatic plant Spirodela polyrrhiza was examined for direct blue 129 (DB129) azo dye. The dye removal efficiency was optimized under the variable conditions of the operational parameters including removal time, initial dye concentration, pH, temperature and amount of plant. The study reflected the significantly enhanced dye removal efficiency of S. polyrrhiza by increasing the temperature, initial dye concentration and amount of plant. Intriguingly, artificial neural network (ANN) predicted the removal time as the most dominant parameter on DB129 removal efficiency. Furthermore, the effect of dye treatment on some physiologic indices of S. polyrrhiza including growth rate, photosynthetic pigments content, lipid peroxidation and antioxidant enzymes were studied. The results revealed a reduction in photosynthetic pigments content and in multiplication of fronds after exposure to dye solution. In contrast, malondialdehyde content as well as catalase (CAT) and peroxidase (POD) activities significantly increased that was probably due to the ability of plant to overcome oxidative stress. As a result of DB129 biodegradation, a number of intermediate compounds were identified by gas chromatography–mass spectroscopy (GC–MS) analysis. Accordingly, the probable degradation pathway of DB129 in S. polyrrhiza was postulated.     

Biotransformation of 4-sec-butylphenol by Gram-positive bacteria of the genera Mycobacterium and Nocardia including modifications on the alkyl chain and the hydroxyl group

The environmental pollutant 4-sec-butylphenol (4-sec-BP) which possesses estrogenic properties was transformed by the aerobic Gram-positive bacteria Mycobacterium neoaurum and Nocardia cyriacigeorgica into three main products (P1–P3) which were isolated and structurally characterized in detail. Two of them were products of a process resembling anaerobic metabolism of alkylphenols based on modifications of the alkyl side chain of 4-sec-BP. The first product (P1) was identified as 4-(2-hydroxy-1-methylpropyl)-phenol. The second product P2 was isolated as a mixture of at least four structures which could be identified as I 4-sec-butylidenecyclohexa-2,5-dienone; II 4-(1-methylenepropyl)-phenol; III 4-(1-methylpropenyl)-phenol; and IV 4-(1-methylallyl)-phenol. In contrast to P1 and P2, the third product (P3) resulted from a modification of the hydroxyl group of 4-sec-BP. This product was only formed by M. neoaurum and was identified as the glucoside conjugate 4-sec-butylphenol-α-d-glucopyranoside. Since in general, fungi synthesize sugar conjugates to detoxify hazardous pollutants, the formation of this conjugate is a peculiarity of M. neoaurum. Thus, altogether, six products were formed from 4-sec-BP and different transformation pathways are introduced. The hydroxylating and glucosylating capacity of the characterized bacteria open up applications in environmental protection.     

Biodegradation of 4-bromophenol by Arthrobacter chlorophenolicus A6 in batch shake flasks and in a continuously operated packed bed reactor

The present study investigated growth and biodegradation of 4-bromophenol (4-BP) by Arthrobacter chlorophenolicus A6 in batch shake flasks as well as in a continuously operated packed bed reactor (PBR). Batch growth kinetics of A. chlorophenolicus A6 in presence of 4-BP followed substrate inhibition kinetics with the estimated biokinetic parameters value of μ _max = 0.246 h^?1, K _i = 111 mg L^?1, K _s  = 30.77 mg L^?1 and K = 100 mg L^?1. In addition, variations in the observed and theoretical biomass yield coefficient and maintenance energy of the culture were investigated at different initial 4-BP concentration. Results indicates that the toxicity tolerance and the biomass yield of A. chlorophenolicus A6 towards 4-BP was found to be poor as the organism utilized the substrate mainly for its metabolic maintenance energy. Further, 4-BP biodegradation performance by the microorganism was evaluated in a continuously operated PBR by varying the influent concentration and hydraulic retention time in the ranges 400–1,200 mg L^?1 and 24–7.5 h, respectively. Complete removal of 4-BP was achieved in the PBR up to a loading rate of 2,276 mg L^?1 day^?1.     

Isolation and Characterization of 4-tert-Butylphenol-Utilizing Sphingobium fuliginis Strains from Phragmites australis Rhizosphere Sediment

We isolated three Sphingobium fuliginis strains from Phragmites australis rhizosphere sediment that were capable of utilizing 4-tert-butylphenol as a sole carbon and energy source. These strains are the first 4-tert-butylphenol-utilizing bacteria. The strain designated TIK-1 completely degraded 1.0 mM 4-tert-butylphenol in basal salts medium within 12 h, with concomitant cell growth. We identified 4-tert-butylcatechol and 3,3-dimethyl-2-butanone as internal metabolites by gas chromatography-mass spectrometry. When 3-fluorocatechol was used as an inactivator of meta-cleavage enzymes, strain TIK-1 could not degrade 4-tert-butylcatechol and 3,3-dimethyl-2-butanone was not detected. We concluded that metabolism of 4-tert-butylphenol by strain TIK-1 is initiated by hydroxylation to 4-tert-butylcatechol, followed by a meta-cleavage pathway. Growth experiments with 20 other alkylphenols showed that 4-isopropylphenol, 4-sec-butylphenol, and 4-tert-pentylphenol, which have alkyl side chains of three to five carbon atoms with α-quaternary or α-tertiary carbons, supported cell growth but that 4-n-alkylphenols, 4-tert-octylphenol, technical nonylphenol, 2-alkylphenols, and 3-alkylphenols did not. The rate of growth on 4-tert-butylphenol was much higher than that of growth on the other alkylphenols. Degradation experiments with various alkylphenols showed that strain TIK-1 cells grown on 4-tert-butylphenol could degrade 4-alkylphenols with variously sized and branched side chains (ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, tert-butyl, n-pentyl, tert-pentyl, n-hexyl, n-heptyl, n-octyl, tert-octyl, n-nonyl, and branched nonyl) via a meta-cleavage pathway but not 2- or 3-alkylphenols. Along with the degradation of these alkylphenols, we detected methyl alkyl ketones that retained the structure of the original alkyl side chains. Strain TIK-1 may be useful in the bioremediation of environments polluted by 4-tert-butylphenol and various other 4-alkylphenols.4-tert-Butylphenol is an alkylphenol with a tertiary branched side chain of four carbon atoms at the para position of phenol. It is an industrially important chemical and is abundantly and widely used for the production of phenolic, polycarbonate, and epoxy resins. Production of 4-tert-butylphenol in the European Union in 2001 was 25,251 tons (t) (9). In Japan, according to the National Institute of Technology and Evaluation (http://www.safe.nite.go.jp/english/sougou/view/ComprehensiveInfoDisplay_en.faces), production of 4-tert-butylphenol amounted to 27,761 t in 2007. 4-tert-Butylphenol is widely distributed in aquatic environments, including river waters (20), seawaters (17), river sediments (17), marine sediments (23), and effluent samples from sewage treatment plants and wastewater treatment plants (22). Furthermore, 4-tert-butylphenol interacts with estrogen receptors (29, 30, 34, 35, 39) and exhibits other toxic effects on aquatic organisms and humans (4, 15, 16, 25, 26, 42, 43). Therefore, it is necessary to study the biodegradation of 4-tert-butylphenol to understand its fate in the aquatic environment, to establish technologies to treat the waters polluted by it, and to remove it from contaminated environments.Studies of the biodegradation of alkylphenols have focused mainly on branched 4-nonylphenol. Several strains of sphingomonad bacteria, including Sphingomonas sp. strain TTNP3 (38), Sphingobium xenophagum Bayram (11), and Sphingomonas cloacae S-3^T (10), have recently been isolated from activated sludge. These strains can degrade branched 4-nonylphenol and utilize it as a sole carbon source. In addition, several Pseudomonas strains that can degrade medium-chain 4-n-alkylphenols (e.g., 4-n-butylphenol) and utilize them as sole carbon sources have been isolated from activated sludge or contaminated soil; they include Pseudomonas veronii INA06 (1), Pseudomonas sp. strain KL28 (21), and Pseudomonas putida MT4 (36). Biodegradation of branched 4-nonylphenol and 4-n-butylphenol has been well studied, but little is known about the biodegradation of 4-tert-butylphenol, although this compound has a structure similar to those of branched 4-nonylphenol and 4-n-butylphenol. There is only one report on the biotransformation of 4-tert-butylphenol—by resting cells of S. xenophagum strain Bayram grown on technical nonylphenol—but this strain cannot grow on 4-tert-butylphenol (11, 14). To our knowledge, there are no reports of bacteria that utilize 4-tert-butylphenol as the sole carbon source, and the biochemical pathway of 4-tert-butylphenol utilization has not been described.Here we characterize three Sphingobium fuliginis strains—TIK-1, TIK-2, and TIK-3—isolated from rhizosphere sediment of the reed Phragmites australis. These strains could use 4-tert-butylphenol as a sole carbon source. On the basis of additional tests of strain TIK-1, we propose that it degrades 4-tert-butylphenol through 4-tert-butylcatechol along a meta-cleavage pathway. We also show that strain TIK-1 cells grown on 4-tert-butylphenol can degrade a wide range of 4-alkylphenols via a meta-cleavage pathway.     

Stimulation of nitrogen removal in the rhizosphere of aquatic duckweed by root exudate components

Plants can stimulate bacterial nitrogen (N) removal by secretion of root exudates that may serve as carbon sources as well as non-nutrient signals for denitrification. However, there is a lack of knowledge about the specific non-nutrient compounds involved in this stimulation. Here, we use a continuous root exudate-trapping system in two common aquatic duckweed species, Spirodela polyrrhiza (HZ1) and Lemna minor (WX3), under natural and aseptic conditions. An activity-guided bioassay using denitrifying bacterium Pseudomonas fluorescens showed that crude root exudates of the two species strongly enhanced the nitrogen-removal efficiency (NRE) of P. fluorescens (P < 0.05) under both conditions. Water-insoluble fractions (F) obtained under natural conditions stimulated NRE to a significant extent, promoting rates by about 30 %. Among acidic, neutral and basic fractions, a pronounced stimulatory effect was also observed for the neutral fractions from HZ1 and WX3 under both conditions, whereas the acidic fractions from WX3 displayed an inhibitory effect. Analysis of the active fractions using gas chromatography/mass spectrometry (GC/MS) revealed that duckweed released fatty acid methyl esters and fatty acid amides, specifically: methyl hexadecanoate, methyl (Z)-7-hexadecenoate, methyl dodecanoate, methyl-12-hydroxystearate, oleamide, and erucamide. Methyl (Z)-7-hexadecenoate and erucamide emerged as the effective N-removal stimulants (maximum stimulation of 25.9 and 33.4 %, respectively), while none of the other tested compounds showed stimulatory effects. These findings provide the first evidence for a function of fatty acid methyl esters and fatty acid amides in stimulating N removal of denitrifying bacteria, affording insight into the “crosstalk” between aquatic plants and bacteria in the rhizosphere.     

Tracking the source of Bacillus thuringiensis Cry1Ab endotoxin in the environment

The application of Bacillus thuringiensis (Bt) and the growing of genetically-modified crops are currently practised to control infestations of crop-eating insects. The increasing use of these biopesticides could lead to an increase in Cry1Ab endotoxin in both terrestrial and aquatic environments. The aim of this study was to quantify levels of Cry1Ab endotoxin and locate its source in the environment. Agricultural soils and surface waters were spiked with crystals (biopesticide-Dipel^®) or with pure Bt-corn endotoxin. Cry1Ab concentrations were then determined with immunoassays. Additionally, surface water, soils and sediments were sampled in an area sprayed with Bt kurstaki and at a site where genetically-modified corn expressing Cry1Ab is grown. Isotopic analysis was performed on the endotoxin from Bt and Bt corn to characterize the proportions of ¹³C/¹²C and ¹⁵N/¹⁴N. The results showed that Bt-corn endotoxin is degraded more rapidly in water than in soils (t_1/2: 4 and 9 days, respectively), while crystals appeared to be more resilient, as expected. The isotopic patterns of ¹³C and ¹⁵N in Bt-corn endotoxin differed markedly from Bt, making it possible to track the source of Cry1Ab in the environment. Preliminary field surveys indicate that Cry1Ab is fairly uncommon in aquatic environments, being found only at trace concentrations when it is detected.     

Carbon dioxide assimilation from air and water by duckweed Spirodela polyrrhiza (L.) Schleid

Carbon dioxide assimilation by duckweed, S. polyrrhiza, was measured using a glass assimilation box and ¹⁴C-NaHCO₃, under different pH conditions of water. S. polyrrhiza assimilates carbon dioxide from both air and water. The carbon assimilation from air is comparable to the assimilation from water under normal pH conditions.     

Degradation of Polycyclic Aromatic Hydrocarbons at Low Temperature under Aerobic and Nitrate-Reducing Conditions in Enrichment Cultures from Northern Soils

The potential for biodegradation of polycyclic aromatic hydrocarbons (PAHs) at low temperature and under anaerobic conditions is not well understood, but such biodegradation would be very useful for remediation of polluted sites. Biodegradation of a mixture of 11 different PAHs with two to five aromatic rings, each at a concentration of 10 μg/ml, was studied in enrichment cultures inoculated with samples of four northern soils. Under aerobic conditions, low temperature severely limited PAH biodegradation. After 90 days, aerobic cultures at 20°C removed 52 to 88% of the PAHs. The most extensive PAH degradation under aerobic conditions at 7°C, 53% removal, occurred in a culture from creosote-contaminated soil. Low temperature did not substantially limit PAH biodegradation under nitrate-reducing conditions. Under nitrate-reducing conditions, naphthalene, 2-methylnaphthalene, fluorene, and phenanthrene were degraded. The most extensive PAH degradation under nitrate-reducing conditions at 7°C, 39% removal, occurred in a culture from fuel-contaminated Arctic soil. In separate transfer cultures from the above Arctic soil, incubated anaerobically at 7°C, removal of 2-methylnaphthalene and fluorene was stoichiometrically coupled to nitrate removal. Ribosomal intergenic spacer analysis suggested that enrichment resulted in a few predominant bacterial populations, including members of the genera Acidovorax, Bordetella, Pseudomonas, Sphingomonas, and Variovorax. Predominant populations from different soils often included phylotypes with nearly identical partial 16S rRNA gene sequences (i.e., same genus) but never included phylotypes with identical ribosomal intergenic spacers (i.e., different species or subspecies). The composition of the enriched communities appeared to be more affected by presence of oxygen, than by temperature or source of the inoculum.     

Biodegradation of alkyl branched aromatic alkanoic naphthenic acids by Pseudomonas putida KT2440

The majority of the world’s crude oil reserves consist of highly biodegraded heavy and super heavy crude oils and oil sands that have not yet been fully exploited. These vast resources contain complex mixtures of carboxylic acids known as naphthenic acids (NAs). NAs cause major environmental and economic problems, as they are recalcitrant, corrosive and toxic. Although aromatic acids make up a small proportion of most NA mixtures, they have demonstrable toxicities to some organisms (e.g. some bacteria and algae) and ideally need to be removed or reduced by remediation. The present study analysed the ability of Pseudomonas putida KT2440 to degrade highly recalcitrant aromatic acids, as exemplified by the alkyl phenylalkanoic acid (4′-t-butylphenyl)-4-butanoic acid (t-BPBA) and the more degradable (4′-n-butylphenyl)-4-butanoic acid (n-BPBA). n-BPBA was completely metabolized after 14 days, with the production of a persistent metabolite identified as (4′-n-butylphenyl)ethanoic acid (BPEA) which resulted from removal of two carbon atoms from the carboxyl side chain (beta-oxidation) as observed previously with a mixed consortium. However, when n-BPBA concentration was increased two-fold, degradation decreased by 56% with a concomitant six-fold decrease in cell numbers, suggesting that at greater concentrations, n-BPBA may be toxic to P. putida KT2440. In contrast, P. putida KT2440 was unable to degrade the highly recalcitrant t-BPBA even after 49 days. These findings have implications for NA bioremediation in the environment.     

Purification of heparinase and heparitinase by affinity chromatography on glycosaminoglycan-bound ah-sepha-rose 4b

Heparinase and heparitinase were separated from an extract of Flavobacterium heparinum, induced with heparin by using column chromatography on hydroxylapatite. As the heparinase preparation contained chondroitinases B and C, chondroitinase B was removed by rechromatography on a hydroxylapatite column. Chondroitinase C was then eliminated by column chromatography on O-phosphono(“phospho”)-cellulose. The heparinase preparation thus obtained was free from sulfoamidase for 2-deoxy-2-sulfoamino-D-glucose (GlcN-2S), sulfatase for 2-amino-2-deoxy-6-O-sulfo D-glucose (GlcN-6S), as well as (δ_4,5glycosiduronase for the unsaturated disaccharides obtained from heparin. The remaining sulfatase for 4-deoxy-α-L-thero-hex-4-enopyranosyluronic acid 2-sulfate (δUA-2S) in the heparinase preparation was removed by affinity chromatography with dermatan sulfate-bound AH-Sepharose 4B coated with dermatan sulfate. The heparitinase preparation separated by column chromatography on hydroxyla patite was purified by affinity chromatography with heparin-bound AH-Sepharose 4B coated with heparin. Sulfatase for 2-amino-2-deoxy-6-O-sulfo-D-glucose (GlcN-6S) and δ_4,5glycosiduronase for the unsaturated disaccharides obtained from heparin were removed by this chromatography. Sulfatase for 4-deoxy-α-L-threo-hex-4-enopyranosyluronic acid 2-sulfate (δUA-2S) remaining in the heparitinase preparation was finally removed by column chromatography on hydroxylapatite. The recoveries of the purified preparations of heparinase and heparitinase were estimated to be 39 and 50%, respectively, from the crude enzyme fractions obtained by the first column chromatography on hydroxyl- patite. The purified heparinase and heparitinase were free from all enzymes that could degrade the sulfated unsaturated disaccharides produced from heparin with heparinase.     

Biodegradation and metabolic pathway of sulfamethoxazole by Pseudomonas psychrophila HA-4, a newly isolated cold-adapted sulfamethoxazole-degrading bacterium

Sulfamethoxazole is a common antibiotic that is frequently detected in wastewater and surface water. This study investigated the biodegradation and metabolic pathway of sulfamethoxazole by Pseudomonas psychrophila HA-4, a cold-adapted bacterium. Strain HA-4, which uses sulfamethoxazole as its sole source of carbon and energy, was isolated at a low temperature (10 °C) and identified as P. psychrophila by physico-biochemical characterization and 16S rRNA gene sequence analysis. Strain HA-4 removed sulfamethoxazole at temperatures ranging from 5.0 °C to 30 °C, with the maximal removal rate at 10 °C. The maximal removal rate of sulfamethoxazole by strain HA-4 was 34.30 % after 192 h at 10 °C. The highest percentage of unsaturated fatty acid was determined to be 23.03 % at 10 °C, which adheres to the characteristic for cold-adapted psychrophiles and psychrotrophs. At low concentrations of sulfamethoxazole, the growth kinetics correlated well with the Haldane model. The single-substrate parameter values of sulfamethoxazole on cell growth were determined to be μ _max?=?0.01 h^?1, K _s?=?20.91 mg/l and K _i?=?170.60 mg/l. Additionally, the major intermediates from sulfamethoxazole biodegradation by strain HA-4, including aniline, 3-amino-5-methylisoxazole, 4-aminothiophenol and sulfanilamide, were identified by GC-MS and high-resolution mass spectrometry (HR-MS) analysis. The results demonstrate that strain HA-4 has the potential to degrade sulfamethoxazole at low temperatures.     

Removal of estrogenic activity of iso-butylparaben and n-butylparaben by laccase in the presence of 1-hydroxybenzotriazole

In the presence of a redox mediator, 1-hydroxybenzotriazole (HBT), iso-butylparaben (iso-BP) and n-butylparaben (n-BP) were treated with laccase from white rot fungus Trametes versicolor. HPLC analysis demonstrated that iso-BP and n-BP almost completely disappeared from the reaction mixture after 4 h of treatment with the laccase-HBT system. Using the yeast two-hybrid assay system, it was also confirmed that the laccase-HBT system substantially removed the estrogenic activity of iso-BP and n-BP after 4 h of treatment. Furthermore, there was a linear relationship between the removal of estrogenic activity of both parabens and the decrease in their concentrations. These results demonstrate that the laccase-HBT system is effective in eliminating iso-BP and n-BP, and removing the estrogenic activity of both parabens.     

Biodegradation of the herbicide propanil, and its 3,4-dichloroaniline by-product in a continuously operated biofilm reactor

The persistence of propanil in soil and aquatic environments along with the possible accumulation of toxic degradation products, such as chloroanilines, is of environmental concern. In this work, a continuous small-scale bioprocess to degrade the herbicide propanil, its main catabolic by-product, 3,4-dichloroaniline (3,4-DCA), and the herbicide adjuvants is carried out. A microbial consortium, constituted by nine bacterial genera, was selected. The isolated strains, identified by amplification and sequencing of their 16S rDNA, were: Acidovorax sp., Luteibacter (rhizovicinus), Xanthomonas sp., Flavobacterium sp., Variovorax sp., Acinetobacter (calcoaceticus), Pseudomonas sp., Rhodococcus sp., and Kocuria sp. The ability of the microbial consortium to degrade the herbicide was evaluated in a biofilm reactor at propanil loading rates ranging from 1.9 to 36.8 mg L^?1 h^?1. Complete removal of propanil, 3,4-DCA, chemical oxygen demand and total organic carbon was obtained at propanil loading rates up to 24.9 mg L^?1 h^?1. At higher loading rates, the removal efficiencies decayed. Four of the identified strains could grow individually in propanil, and 3,4-DCA: Pseudomonas sp., Acinetobacter calcoaceticus, Rhodococcus sp., and Xanthomonas sp. The Kokuria strain grew on 3,4-DCA, but not on propanil. The first three bacteria have been related to biodegradation of phenyl urea herbicides or chlorinated anilines. Although some strains of the genera Xanthomonas and Kocuria have a role in the biodegradation of several xenobiotic compounds, as far as we know, there are no reports about degradation of propanil by Xanthomonas or 3,4-DCA by Kocuria species.     

Genomic and Phenotypic Diversity of Coastal Vibrio cholerae Strains Is Linked to Environmental Factors

Studies of Vibrio cholerae diversity have focused primarily on pathogenic isolates of the O1 and O139 serotypes. However, autochthonous environmental isolates of this species routinely display more extensive genetic diversity than the primarily clonal pathogenic strains. In this study, genomic and metabolic profiles of 41 non-O1/O139 environmental isolates from central California coastal waters and four clinical strains are used to characterize the core genome and metabolome of V. cholerae. Comparative genome hybridization using microarrays constructed from the fully sequenced V. cholerae O1 El Tor N16961 genome identified 2,787 core genes that approximated the projected species core genome within 1.6%. Core genes are almost universally present in strains with widely different niches, suggesting that these genes are essential for persistence in diverse aquatic environments. In contrast, the dispensable genes and phenotypic traits identified in this study should provide increased fitness for certain niche environments. Environmental parameters, measured in situ during sample collection, are correlated to the presence of specific dispensable genes and metabolic capabilities, including utilization of mannose, sialic acid, citrate, and chitosan oligosaccharides. These results identify gene content and metabolic pathways that are likely selected for in certain coastal environments and may influence V. cholerae population structure in aquatic environments.     

Biodegradation of 4-nitroanisole by two Rhodococcus spp.

Two Rhodococcus strains, R. opacus strain AS2 and R. erythropolis strain AS3, that were able to use 4-nitroanisole as the sole source of carbon and energy, were isolated from environmental samples. The first step of the degradation involved the O-demethylation of 4-nitroanisole to 4-nitrophenol which accumulated transiently in the medium during growth. Oxygen uptake experiments indicated the transformation of 4-nitrophenol to 4-nitrocatechol and 1,2,4-trihydroxybenzene prior to ring cleavage and then subsequent mineralization. The nitro group was removed as nitrite, which accumulated in the medium in stoichiometric amounts. In R. opacus strain AS2 small amounts of hydroquinone were produced by a side reaction, but were not further degraded.     

Biodegradation of pyrene by Candida sp. S1 under high salinity conditions

Polycyclic aromatic hydrocarbon is a toxic recalcitrant environmental pollutant and its removal from the environment is very essential. In this study, a novel S1 strain isolated from the tropical rain forest was identified as Candida species based on 18S rRNA. The pyrene biodegradation was performed by Candida sp. S1. Pyrene was 35% degraded in 15 days. The percentage of pyrene biodegradation increased up to 75% with 24 g L⁻¹ of sodium chloride and decreased along with increasing salinity. Under the acidic condition, the biodegradation was increased up to 60% at pH 5. It was also found that the increasing glucose concentration of more than 10 g L⁻¹ had no significant effect on pyrene biodegradation, while agitation proved to have greater influence. There was a positive relationship between biomass growth and biodegradation rate of pyrene. One pyrene metabolite was identified from the extract solution and analyzed by a thin-layer chromatography, UV–visible absorption and gas chromatography–mass spectrometry. The metabolite found in the pyrene degradation was benzoic acid. Suitable conditions must be found to promote a successful microbial augmentation in liquid culture.

     

Archaeal and bacterial communities of heavy metal contaminated acidic waters from zinc mine residues in Sepetiba Bay

Mining of metallic sulfide ore produces acidic water with high metal concentrations that have harmful consequences for aquatic life. To understand the composition and structure of microbial communities in acid mine drainage (AMD) waters associated with Zn mine tailings, molecular diversity of 16S genes was examined using a PCR, cloning, and sequencing approach. A total of 78 operational taxonomic units (OTUs) were obtained from samples collected at five different sites in and around mining residues in Sepetiba Bay, Brazil. We analyzed metal concentration, physical, chemical, and microbiological parameters related to prokaryotic diversity in low metal impacted compared to highly polluted environments with Zn at level of gram per liter and Cd–Pb at level of microgram per liter. Application of molecular methods for community structure analyses showed that Archaea and Bacteria groups present a phylogenetic relationship with uncultured environmental organisms. Phylogenetic analysis revealed that bacteria present at the five sites fell into seven known divisions, α-Proteobacteria (13.4%), β-Proteobacteria (16.3%), γ-Proteobacteria (4.3%), Sphingobacteriales (4.3%), Actinobacteria (3.2%) Acidobacteria (2.1%), Cyanobacteria (11.9%), and unclassified bacteria (44.5%). Almost all archaeal clones were related to uncultivated Crenarchaeota species, which were shared between high impacted and low impacted waters. Rarefaction curves showed that bacterial groups are more diverse than archaeal groups while the overall prokaryotic biodiversity is lower in high metal impacted environments than in less polluted habitats. Knowledge of this microbial community structure will help in understanding prokaryotic diversity, biogeography, and the role of microorganisms in zinc smelting AMD generation and perhaps it may be exploited for environmental remediation procedures in this area.     

Biodegradation of sulfonamides by <Emphasis Type="Italic">Shewanella oneidensis</Emphasis> MR-1 and <Emphasis Type="Italic">Shewanella</Emphasis> sp. strain MR-4

Because of extensive sulfonamides application in aquaculture and animal husbandry and the consequent increase in sulfonamides discharged into the environment, strategies to remediate sulfonamide-contaminated environments are essential. In this study, the resistance of Shewanella oneidensis MR-1 and Shewanella sp. strain MR-4 to the sulfonamides sulfapyridine (SPY) and sulfamethoxazole (SMX) were determined, and sulfonamides degradation by these strains was assessed. Shewanella oneidensis MR-1 and Shewanella sp. strain MR-4 were resistant to SPY and SMX concentrations as high as 60 mg/L. After incubation for 5 days, 23.91 ± 1.80 and 23.43 ± 2.98% of SPY and 59.88 ± 1.23 and 63.89 ± 3.09% of SMX contained in the medium were degraded by S. oneidensis MR-1 and Shewanella sp. strain MR-4, respectively. The effects of the initial concentration of the sulfonamides and initial pH of the medium on biodegradation, and the degradation of different sulfonamides were assessed. The products were measured by LC–MS; with SPY as a substrate, 2-AP (2-aminopyridine) was the main stable metabolite, and with SMX as a substrate, 3A5MI (3-amino-5-methyl-isoxazole) was the main stable metabolite. The co-occurrence of 2-AP or 3A5MI and 4-aminobenzenesulfonic acid suggests that the initial step in the biodegradation of the two sulfonamides is S–N bond cleavage. These results suggest that S. oneidensis MR-1 and Shewanella sp. strain MR-4 are potential bacterial resources for biodegrading sulfonamides and therefore bioremediation of sulfonamide-polluted environments.