Biodegradation of organic pollutants in saline wastewater by halophilic microorganisms: a review

Agro-food, petroleum, textile, and leather industries generate saline wastewater with a high content of organic pollutants such as aromatic hydrocarbons, phenols, nitroaromatics, and azo dyes. Halophilic microorganisms are of increasing interest in industrial waste treatment, due to their ability to degrade hazardous substances efficiently under high salt conditions. However, their full potential remains unexplored. The isolation and identification of halophilic and halotolerant microorganisms from geographically unrelated and geologically diverse hypersaline sites supports their application in bioremediation processes. Past investigations in this field have mainly focused on the elimination of polycyclic aromatic hydrocarbons and phenols, whereas few studies have investigated N-aromatic compounds, such as nitro-substituted compounds, amines, and azo dyes, in saline wastewater. Information regarding the growth conditions and degradation mechanisms of halophilic microorganisms is also limited. In this review, we discuss recent research on the removal of organic pollutants such as organic matter, in terms of chemical oxygen demand (COD), dyes, hydrocarbons, N-aliphatic and N-aromatic compounds, and phenols, in conditions of high salinity. In addition, some proposal pathways for the degradation of aromatic compounds are presented.     

Biodegradation capability of Absidia fusca Linnemann towards environmental pollutants

The purpose of this work was to study the bioremediation capability of Absidia fusca Linnemann (Zygomycete) towards different classes of xenobiotics (lignin-derived compounds, chloroaromatic compounds, polycyclic aromatic hydrocarbons) the presence of which in contaminated soils, water and sediments poses a significant risk to the environment and human health. Two strains from different origins were compared. One was from an official collection and grown in non-inducing conditions, while the other was isolated during the course of the survey of fungal flora in a polluted soil from Annaba (Algeria). All data were analyzed and results validated via a statistical treatment. We showed the effect of the factors studied (origin of the strain, xenobiotic) but also the interactions between these factors. The strain of A. fusca isolated from a polluted soil was able to efficiently degrade most of the xenobiotics tested, particularly: pentachlorophenol, phenol, catechol, guaiacol and ferulic acid. This property also existed in the other strain but at a very low level.     

The use of anthracene as a model compound in a comparative study of hydrous pyrolysis methods for industrial waste remediation

Polycyclic aromatic hydrocarbons are very stable compounds and tend to bioaccumulate in the environment due to their high degree of conjugation and aromaticity. Hydrous pyrolysis is explored as a technique for the treatment of industrial water containing PAH, using anthracene as a model compound. The reactivity of anthracene under a range of temperatures and durations are studied in this paper. Aliquots of 1.0-10.0 mg of anthracene in a range of 1.0-5.0 mL of H₂O are subjected to hydrous pyrolysis under varied conditions of temperature, reagents and duration. The conditions include oxidising systems comprising distilled water, hydrogen peroxide and Nafion-SiO₂ solid catalyst in water; and reducing systems of formic acid and formic acid/Nafion-SiO₂/Pd-C catalysts to assess a range of redox reaction conditions. Oxygen in air played a role in some of the reaction conditions. Pyrolysed products were identified and quantified by the use of Gas Chromatography-Mass Spectrometry (GC-MS). The major products were anthrone, anthraquinone, xanthone from oxidation; and multiple hydro-anthracene derivatives from reductive hydogenation. The nature of reaction conditions influenced the extent of anthracene degradation. The products formed are more reactive (less stable) as compared to anthracene the starting material and will therefore be less persistent in the environment.     

Desorption of polycyclic aromatic hydrocarbons from field-contaminated soil to a two-dimensional hydrophobic surface before and after bioremediation

This study investigated environmental distributions and production mechanisms of chlorinated polycyclic aromatic hydrocarbons (Cl-PAHs) in the sediments from some tidal flats located in Asia. Cl-PAHs were found in sediments taken from Arao tidal flat, Kikuchigawa River and Shirakawa River. The range of ∑Cl-PAHs was from 25.5 to 483 pg g⁻¹ for Kikuchigawa River and Arao tidal flat, respectively.Concentrations of PAHs and Cl-PAHs showed no significant correlations (r = 0.134). This result suggests that the origins of these compounds differ. In the identified Cl-PAH isomers, the most abundant Cl-PAH isomer was 9,10-dichloroanthracene (9,10-di-Cl-ANT) in the three sites. In general, concentrations of Cl-ANTs in the coastal environment are about 3-5 orders of magnitude lower than those of anthracene (ANT). However, concentration ratios between Cl-ANTs and ANT (Cl-ANTs/ANT) in the sediments ranged from 4.1% to 24.6%. This result indicated that Cl-PAHs were not generated under industrial processes but the high concentration ratios have resulted from the contribution of photochemical production of Cl-ANTs in the sediments because ANT is known to have high photochemical reactivity.For examining this phenomenon, ANT adsorbed onto glass beads was irradiated with UV under the mimicked field conditions of tidal flats. As a result, it was noticed that, while chlorinated derivatives were negligible in a light-controlled group, production of 2-Cl-ANT, 9-Cl-ANT and 9,10-diCl-ANT on the irradiated surface were found in this study. These results suggest that photochemical reaction of PAHs can be a potential source of the occurrence of Cl-PAHs in the coastal environment.     

Distribution of PAHs in tissues of wetland plants and the surrounding sediments in the Chongming wetland, Shanghai, China

Polycyclic aromatic hydrocarbons (PAHs) concentrations were determined in sediments and three types of wetland plants collected from the intertidal flats in the Chongming wetland. The concentration of total PAHs in sediments ranged from 38.7 to 136.2 ng g⁻¹. Surface sediment concentrations were higher in regions with plant cover than in bare regions. Rhizome-layer sediments (56.8-102.4 ng g⁻¹) contained less PAHs than surface sediments (0-5 cm). Concentrations of PAHs in plant tissues ranged from 51.9 to 181.2 ng g⁻¹, with highest concentrations in the leaves of Scirpus. Most of the PAHs in the leaves and other plant tissues were low molecular weight compounds (LMW, 2-4 rings), and a similar distribution pattern of PAHs in different types of plants was also observed. Source analysis indicated that plants and sediments both came from pyrogenic sources, but plants had additional petroleum contamination. The low ratio of benzo[a]anthracene over chrysene suggests that the wetland PAHs came mainly from long-distance atmospheric transportation. Significant bioaccumulation of PAHs from the sediments into plants was not observed for high molecular weight PAHs (HMW, 5-6 rings) in Chongming wetland. The small RCFs (root concentration factor from sediments) for HMW PAHs and large RCFs for LMW PAHs suggested that roots accumulated LMW PAHs selectively from sediments in Chongming wetland.     

Enhanced degradation of polycyclic aromatic hydrocarbons by biodegradation combined with a modified Fenton reaction

A study has been conducted to enhance degradation of a mixture of polycyclic aromatic hydrocarbons (PAHs) by combining biodegradation with hydrogen peroxide oxidation in a former manufactured gas plant (MGP) soil. An active bacterial consortium enriched from the MGP surface soil (0-2 m) biodegraded more than 90% of PAHs including 2-, 3-, and 4-ring hydrocarbons in a model soil. The consortium was also able to transform about 50% of 4- and 5-ring hydrocarbons in the MGP soil. As a chemical oxidant, Fenton's reagent (H2O2 + Fe2+) was very efficient in the destruction of a mixture of PAHs (i.e., naphthalene (NAP), fluorene (FLU), phenanthrene (PHE), anthracene (ANT), pyrene (PYR), chrysene (CHR), and benzo(a)pyrene (BaP)) in the model soil; noticeably, 84.5% and 96.7% of initial PYR and BaP were degraded, respectively. In the MGP soil, the same treatment destroyed more than 80% of 2- and 3-ring hydrocarbons and 20-40% of 4- and 5-ring compounds. However, the low pH requirement (pH 2-3) for optimum Fenton reaction made the process incompatible with biological treatment and posed potential hazards to the soil ecosystem where the reagent was used. In order to overcome such limitation, a modified Fenton-type reaction was performed at near neutral pH by using ferric ions and chelating agents such as catechol and gallic acid. By the combined treatment of the modified Fenton reaction and biodegradation, more than 98% of 2- or 3-ring hydrocarbons and between 70% and 85% of 4- or 5-ring compounds were degraded in the MGP soil, while maintaining its pH about 6-6.5.     

Observations on the preferential biodegradation of selected components of polyaromatic hydrocarbon mixtures

The capacity of the naphthalene degrading enzyme (NAH) system of Pseudomonas fluorescens 5R and a number of other NAH system bacterial isolates to degrade mixtures of polyaromatic hydrocarbons (PAHs) and heterocyclic compounds were examined. It was found that all the examined organisms displayed similar patterns of preferential compound degradation when presented with the same mixture. Using strains that possess portions of the NAH system, this preferential degradation was localized to the activity of naphthalene dioxygenase. Comparisons of the first-order rates of compound degradation with the structures of the mixture components indicated that increased deviation from the base structure of naphthalene led to slower disappearance. Structural features that were found to decrease the rate of compound degradation include an increase in the number of methyl substituents and an increase in the size of a substituent.     

Oxidation of polycyclic aromatic hydrocarbons by fungal isolates from an oil contaminated refinery soil

BACKGROUND AND OBJECTIVE: Indigenous soil microorganisms are used for the biodegradation of petroleum hydrocarbons in oily waste residues from the petroleum refining industry. The objective of this investigation was to determine the potential of indigenous strains of fungi in soil contaminated with petroleum hydrocarbons to biodegrade polycyclic aromatic hydrocarbons (PAH). MATERIALS AND METHODS: Twenty one fungal strains were isolated from a soil used for land-farming of oily waste residues from the petrochemical refining industry in Singapore and identified to genus level using laboratory culture and morphological techniques. Isolates were incubated in the presence of 30 mg/L of phenanthrene over a period of 28 days at 30 degrees C. The most effective strain was further evaluated to determine its ability to oxidise a wider range of PAH compounds of various molecular weight i.e acenaphthene, fluorene, fluoranthene, chrysene, benzo(a)pyrene and dibenz(ah)anthracene RESULTS AND DISCUSSION: After 28 days of incubation, 18 of the 21 fungal cultures were capable of oxidising over 50% of the phenanthrene present in culture medium, relative to abiotic controls. Fungal isolate, Penicillium sp. 06, was able to oxidise 89% of the phenanthrene present. This isolate could also oxidise more than 75% of the acenaphthene, fluorene and fluoranthene after 30 days of incubation. However, the oxidation of high molecular weight PAH i.e. chrysene, benzo(a)pyrene and dibenz(ah)anthracene by the Penicillium sp. 06 isolate was limited, where the extent of oxidation was inversely proportional to PAH molecular weight. CONCLUSIONS: Fungal isolate, Penicillium sp. 06, was effective at oxidising a range of PAH in petroleum contaminated soils, but higher molecular weight PAH were more recalcitrant. RECOMMENDATIONS AND OUTLOOK: There is potential for the re-application of this fungal strain to soil for bioremediation purposes.     

Isolation and characterization of mesotrione-degrading Bacillus sp. from soil

Dissipation kinetics of mesotrione, a new triketone herbicide, sprayed on soil from Limagne (Puy-de-Dôme, France) showed that the soil microflora were able to biotransform it.Bacteria from this soil were cultured in mineral salt solution supplemented with mesotrione as sole source of carbon for the isolation of mesotrione-degrading bacteria. The bacterial community structure of the enrichment cultures was analyzed by temporal temperature gradient gel electrophoresis (TTGE). The TTGE fingerprints revealed that mesotrione had an impact on bacterial community structure only at its highest concentrations and showed mesotrione-sensitive and mesotrione-adapted strains. Two adapted strains, identified as Bacillus sp. and Arthrobacter sp., were isolated by colony hybridization methods.Biodegradation assays showed that only the Bacillus sp. strain was able to completely and rapidly biotransform mesotrione. Among several metabolites formed, 2-amino-4-methylsulfonylbenzoic acid (AMBA) accumulated in the medium. Although sulcotrione has a chemical structure closely resembling that of mesotrione, the isolates were unable to degrade it.     

Biodegradation of aliphatic and aromatic hydrocarbons by natural soil microflora and pure cultures of imperfect and lignolitic fungi

The biodegradation of aliphatic and aromatic hydrocarbons by natural soil microflora and seven fungi species, including imperfect strains and higher level lignolitic species, is compared in a 90-day laboratory experiment using a natural, not-fertilized soil contaminated with 10% crude oil. The natural microbial soil assemblage isolated from an urban forest area was unable to significantly degrade crude oil, whereas pure fungi cultures effectively reduced the residues by 26-35% in 90 days. Normal alkanes were almost completely degraded in the first 15 days, whereas aromatic compounds (phenanthrene and methylphenanthrenes) exhibited slower kinetics. Aspergillus terreus and Fusarium solani, isolated from oil-polluted areas, produced the more efficient attack of aliphatic and aromatic hydrocarbons, respectively. Overall, imperfect fungi isolated from polluted soils showed a somewhat higher efficiency, but the performance of unadapted, indigenous, lignolitic fungi was comparable, and all three species, Pleurotus ostreatus, Trametes villosus and Coriolopsis rigida, effectively degraded aliphatic and aromatic components. The simultaneous, multivariate analysis of 22 parameters allowed the elucidation of a clear reactivity trend of the oil components during biodegradation: lower molecular weight n-alkanes > phenanthrene > 3-2-methylphenanthrenes > intermediate chain length n-alkanes > longer chain length n-alkanes > isoprenoids approximately 9-1-methylphenanthrenes. Irrespective of the individual degrading capacities, all fungi species tested seem to follow this decomposition sequence.     

Synthesis of zirconia-immobilized copper chelates for catalytic decomposition of hydrogen peroxide and the oxidation of polycyclic aromatic hydrocarbons

Chelating sorbents with diethylenetriaminepenta(methylene-phosphonic acid) (DTPMPA) and ethylenediaminetetraacetic acid ligands immobilized on zirconia matrix were prepared and subsequently saturated with Cu(II). All the Cu chelates catalyzed decomposition of H(2)O(2) yielding highly reactive hydroxyl radicals. All of them were also able to catalyze degradation of polycyclic aromatic hydrocarbons (anthracene, benzo[a]pyrene and benzo[b]fluoranthene). The most effective DTPMPA-based catalysts G-32 and G-35 (10 mg ml(-1) with 100 mmol H(2)O(2)) caused almost complete decomposition of 15 ppm anthracene and benzo[a]pyrene during a five day catalytic cycle at 30 degrees C. Anthracene-1,4-dione was the main product of anthracene oxidation by all catalysts. The catalysts were active in several cycles without regeneration.     

Reduction of selenite to red elemental selenium by moderately halotolerant Bacillus megaterium strains isolated from Bhitarkanika mangrove soil and characterization of reduced product

Two Gram (+) bacterial strains, BSB6 and BSB12, showing resistance and potential for Se(IV) reduction among 26 moderately halotolerant isolates from the Bhitarkanika mangrove soil were characterized by biochemical and 16S rDNA sequence analyses. Both of them were strictly aerobic and able to grow in a wide range of pH (4-11), temperature (4-40 °C) and salt concentration (4-12%) having an optimum growth at 37 °C, pH ∼7.5 and 7% salt (NaCl). The biochemical characteristics and 16S rDNA sequence analysis of BSB6 and BSB12 showed the closest phylogenetic similarity with the species Bacillus megaterium. Both the strains effectively reduced Se(IV) and complete reduction of selenite (up to 0.25 mM) was achieved within 40 h. SEM with energy dispersive X-ray and TEM analyses revealed the formation of nano size spherical selenium particles in and around the bacterial cells which were also supported by the confocal micrograph study. The UV-Vis diffuse reflectance spectra and XRD of selenium precipitates revealed that the selenium particles are in the nanometric range and crystalline in nature. These bacterial strains may be exploited further for bioremediation process of Se(IV) at relatively high salt concentrations and green synthesis of selenium nanoparticles.     

The effect of temperature on the rate of disappearance of polycyclic aromatic hydrocarbons from soils

The effect of temperature on the range and rate of disappearance of four polycyclic aromatic hydrocarbons (PAHs; fluorene, anthracene, pyrene and chrysene) added as a mixture of pure compounds to two different soils (light loam and loamy sand) was investigated over 180 days in a laboratory experiment. An increase in temperature from 10 to 25 degrees C enhanced the losses of all four PAHs from both soils. The effect of temperature on the rate of PAH disappearance depended on the physico-chemical properties of the compound and of the soil. The long half-lives at lower temperatures as obtained in the laboratory tests may suggest high persistence of higher molecular weight PAHs under some field conditions.     

GC/MS analysis of polynuclear aromatic hydrocarbons in sediment samples from the Niger Delta region

Thirteen sediment samples from different locations in the Niger Delta region of Nigeria were analyzed for the presence of 16 polynuclear aromatic hydrocarbons (PAHs) via gas chromatography/mass spectrometry. The specific target compounds for this study included naphthalene, acenaphthylene, acenaphthene, flourene, phenanthrene, anthracene, flouranthene, pyrene, benz[a]anthracene, chrysene, benzo[b]fluoranthene, benzo[k]flouranthene, benzo[a]pyrene, benzo[ghi]perylene, dibenz[a,h]anthracene, and indeno[1,2,3-cd]pyrene. Four isotopically labeled polynuclear aromatic hydrocarbons (acanaphthene-d10, phenanthrene-d10, chrysene-d12 and perylene-d12) were used for internal standardization. All 16 PAHs were found in most of the thirteen samples with concentration ranging from 0.1 microg/kg to 28 microg/kg. It was also found that the 5 and 6-ring PAHs were present in higher concentrations than all the other compounds, indicating their high resistance to microbial degradation.     

Crude oil and hydrocarbon-degrading strains of Rhodococcus rhodochrous isolated from soil and marine environments in Kuwait

Soil and marine samples collected from different localities in Kuwait were screened for microorganisms capable of oil degradation. Both fungi and bacteria were isolated. The fungal flora consisted of Aspergillus terreus, A. sulphureus, Mucor globosus, Fusarium sp. and Penicillum citrinum. Mucor globosus was the most active oil degrading fungus isolated. Bacterial isolates included Bacillus spp. Enterobacteriaceae, Pseudomonas spp., Nocardia spp., Streptomyces spp.,and Rhodococcus spp. Among these Rhodococcus strains were the most efficient in oil degradation and, relatively speaking, the most abundant. Bacterial and fungal isolates differed in their ability to degrade crude oil, with Rhodococcus isolates being more active that fungin in n-alkane biodegradation, particularly in the case of R. rhodochrous. In addition to medium chain n-alkanes, fungi utilized one or more of the aromatic hydrocarbons studied, while bacteria failed to do so. R. rhodochorous KUCC 8801 was shown by GLC and post-growth studies to be more efficient in oil degradation than isolates known to be active oil degraders.     

Biodegradation of polycyclic aromatic hydrocarbons by a mixed culture

We investigated the potential biodegradation of polycyclic aromatic hydrocarbons (PAHs) by an aerobic mixed culture utilizing phenanthrene as its carbon source. Following a 3-5 h post-treatment lag phase, complete degradation of 5 mg/l phenanthrene occurred within 28 h (optimal conditions determined as 30 degrees C and pH 7.0). Phenanthrene degradation was enhanced by the individual addition of yeast extract, acetate, glucose or pyruvate. Results show that the higher the phenanthrene concentration, the slower the degradation rate. While the mixed culture was also capable of efficiently degrading pyrene and acenaphthene, it failed to degrade anthracene and fluorene. In samples containing a mixture of the five PAHs, treatment with the aerobic culture increased degradation rates for fluorene and anthracene and decreased degradation rates for acenaphthene, phenanthrene and pyrene. Finally, it was observed that when nonionic surfactants were present at levels above critical micelle concentrations (CMCs), phenanthrene degradation was completely inhibited by the addition of Brij 30 and Brij 35, and delayed by the addition of Triton X100 and Triton N101.     

Anaerobic degradation of five polycyclic aromatic hydrocarbons from river sediment in Taiwan

This study investigated the anaerobic degradation of five polycyclic aromatic hydrocarbons (PAHs) from Erren River sediment in southern Taiwan. The degradation rates of PAH were in the order: acenaphthene > fluorene > phenanthrene > anthracene > pyrene. The degradation rate was enhanced when the five compounds were present simultaneously in river sediment. Comparison of the PAH degradation rates under three reducing conditions showed the following order: sulfate-reducing conditions > methanogenic conditions > nitrate-reducing conditions. The addition of electron donors (acetate, lactate and pyruvate) enhanced PAH degradation under methanogenic and sulfate-reducing conditions. However, the addition of acetate, lactate or pyruvate inhibited PAH degradation under nitrate-reducing conditions. The addition of heavy metals, nonylphenol and phthalate esters (PAEs) inhibited PAH degradation. Our results show that sulfate-reducing bacteria, methanogen and eubacteria are involved in the degradation of PAH; sulfate-reducing bacteria constitute a major microbial component in PAH degradation. Of the microorganism strains isolated from the sediment samples, we found that strain ER9 expressed the greatest biodegrading ability.     

On the aliphatic,and polycyclic aromatic hydrocarbon levels in the southern baltic sea atmosphere

Samples of marine aerosols from the S Baltic Sea have been analysed for aliphatic hydrocarbons from pentadecane to dotriacontane, and for polycyclic aromatic hydrocarbons (PAHs) from anthracene and phenantrene to benzo(ghi)perylene. Some of the sampling stations were situated near industrialized areas (Gdańsk Bay, Pommeranian Bay) and some others in the open Baltic Sea. The aliphatic hydrocarbons were analysed by gas chromatography, polycyclic aromatic hydrocarbons by HPLC. Quantitative composition of the hydrocarbons in the Baltic aerosols is presented and discussed.     

A comparative study on the uptake of polycyclic aromatic hydrocarbons by Anodonta californiensis

Uptake of polycyclic aromatic hydrocarbons (PAHs) by the freshwater bivalve mollusc Anodonta californiensis was examined in the presence and absence of surfactant in order to gain further insight into mixture toxicity and to predict whether certain mixtures have negative and/or positive effects on aquatic organisms. In the presence of surfactant, the uptake of anthracene or chrysene was higher than that of naphthalene, given the same concentration in the solution. In the absence of surfactant, the trend was similar, but the uptakes were increased by approximately 100% compared to those in the presence of surfactant. On the uptake of naphthalene, the presence of anthracene showed only minor influence. The uptake of anthracene was affected by both naphthalene and chrysene. The uptake of chrysene was influenced by neither naphthalene nor anthracene. There was no observable displacement of divalent cations from the surface of the gill membrane by any of the PAHs studied.     

Anaerobic degradation of five polycyclic aromatic hydrocarbons from river sediment in Taiwan

This study investigated the anaerobic degradation of five polycyclic aromatic hydrocarbons (PAHs) from Erren River sediment in southern Taiwan. The degradation rates of PAH were in the order: acenaphthene > fluorene > phenanthrene > anthracene > pyrene. The degradation rate was enhanced when the five compounds were present simultaneously in river sediment. Comparison of the PAH degradation rates under three reducing conditions showed the following order: sulfate-reducing conditions > methanogenic conditions > nitrate-reducing conditions. The addition of electron donors (acetate, lactate and pyruvate) enhanced PAH degradation under methanogenic and sulfate-reducing conditions. However, the addition of acetate, lactate or pyruvate inhibited PAH degradation under nitrate-reducing conditions. The addition of heavy metals, nonylphenol and phthalate esters (PAEs) inhibited PAH degradation. Our results show that sulfate-reducing bacteria, methanogen and eubacteria are involved in the degradation of PAH; sulfate-reducing bacteria constitute a major microbial component in PAH degradation. Of the microorganism strains isolated from the sediment samples, we found that strain ER9 expressed the greatest biodegrading ability.