PAH Degradation Research Articles

Mixed micellization/clouding assisted solubilization of polycyclic aromatic hydrocarbon: Potential in environmental remediation

Micellization and clouding behaviors of an anionic gemini surfactant, phosphoric acid, P, P′‑1,4‑butanedieyl P, P′‑didodecyl ester, disodium salt (12-4-12A), in aqueous solution, have been investigated in the presence of a surface active ionic liquid (SAIL), tetra n‑pentylammonium bromide (TPeAB). Critical micelle concentration and 1H NMR data show synergistic interactions/intercalation of n‑pentyl chain between the 12-4-12A monomers constituting the micelle, respectively. 12-4-12A + TPeAB system showed the cloud point (CP) at distinctly lower [12-4-12A]. Amino acid/cyclodextrin has been used to tune the CP. DLS and TEM data suggest the formation of n‑pentyl chain (of the SAIL) mediated linked aggregates whose size decreases with lowering [TPeAB] while compactness increases by β-CD. POM data showed that larger aggregates are formed near the CP. This may be due to increased hydrophobic interactions (between dodecyl chains of the gemini and pentyl chains of the TPeAB) and decreased electrostatic repulsion (as indicated by lowering zeta-potential value at CP). Mixtures, with or without β-CD, are used for solubilization/co‑solubilization of polyaromatic hydrocarbon (PAHs-anthracene, pyrene or fluorene). Molar solubilization ratio (MSR) has been computed using UV–Visible spectrophotometry. The percentage MSR value increases in order: Anthracene > Pyrene > Fluorene in comparison to pure 12-4-12A. Cloud point extraction of anthracene shows that it concentrates ~93% in surfactant rich phase (SRP). However, anthracene content decreases (~80%) when the system contains β-CD. GZrO2 nanocomposite has shown nearly complete adsorption of anthracene. Strategies, like mixed micellization, tuning of clouding and co-solubilization, can enhance solubility/bioavailability, extraction and subsequent degradation of PAHs from the aquatic/soil environment.

Comparison of microbial community dynamics induced by distinct crude oil dispersions reveals compositional differences

To understand the impact of oil contamination on marine microbial communities, numerous studies have been conducted following microbial dynamics after oil spills and concerning the effects of different environmental parameters on oil biodegradation potential. Nevertheless, there is a lack of understanding of how distinct oil crude types might influence the dynamics of microbial communities of identical origin. Here we show that different crude oils affect the community composition by shaping it distinctly over the course of incubation. We have used chemical dispersion of three crudes with different properties (paraffinic, paraffinic-asphaltenic and naphthenic). Oceanospirillaceae, Colwelliaceae, Porticocacceae, Flavobacteriaceae and Piscirikettsiaceae were highly abundant in all three oil dispersions. However, comparing group distances of the communities at each time point, as well as pairwise fold comparison of OTUs, has revealed significant differences in microbial composition between the oils (p < 0.05), but also between the major families related to biodegradation (p < 0.01). Furthermore, the PAH degradation rates proved to be significantly higher in naphthenic oil (p < 0.05), while the n-alkane degradation was slower, however not significant (p > 0.05). We conclude that different crude oils can shape microbial community distinctively over exposure time, therefore altering community biotransformation potential and causing different degradation rates of targeted oil compounds.

Transcriptional response of Mycobacterium sp. strain A1-PYR to multiple polycyclic aromatic hydrocarbon contaminations

Cometabolism mechanisms of organic pollutants in environmental microbes have not been fully understood. In this study, a global analysis of Mycobacterium sp. strain A1-PYR transcriptomes on different PAH substrates (single or binary of pyrene (PYR) and phenanthrene (PHE)) was conducted. Comparative results demonstrated that expression levels of 23 PAH degradation enzymes were significantly higher in the binary substrate than in the PYR-only one. These enzymes constituted an integrated enzymatic system to actualize all transformation steps of PYR, and most of their encoded genes formed a novel gene cascade in the genome of strain A1-PYR. The roles of different genotypes of enzymes in PYR cometabolism were also discriminated even though all of their gene sequences were presented in the genome of this strain. NidAB and PdoA2B2 instead of NidA3B3 served the initial oxidization of PAHs, and PcaL replaced PcaCD to catalyze the formation of 3-oxoadipate. Novel genes associated with PYR cometabolism was also predicted by the relationships between their transcription profiles and PYR removal. The results showed that ABC-type transporters probably played important roles in the transport of PAHs and their metabolites through cell membrane, and [4Fe-4S] ferredoxin might be essential for dioxygenases (NidAB and PdoA2B2) to achieve oxidative activities. This study provided molecular insight in that microbial degrader subtly cometabolized recalcitrant PAHs with relatively more degradable ones.

Ornamental hyperaccumulator Mirabilis jalapa L. phytoremediating combine contaminated soil enhanced by some chelators and surfactants.

Mirabilis jalapa L. is an ornamental plant of the composite family, which was found hyperaccumulating Cd. Due to its larger biomass, developed root system, root exudation, and microbial interactions, certain organic pollutants in its rhizosphere can be effectively degraded. Thus, M. jalapacan be used to co-remediate heavy metal and organic pollutant co-contaminated soil. The aim of this paper is to explore the remediation capacity of M. jalapa for Cd-PAHs co-contaminated soil in the presence of five chelators or surfactants. The concentrations of Cd and PAHs in collected soil samples were 0.85mgkg-1 Cd and 1.138mgkg-1 PAHs (16 kinds of priority control polycyclic aromatic hydrocarbons by USEPA). The chelators or surfactants of EDTA, EGTA, CA, TW80, and SA were respectively spiked to the pots according to the experiment design at 1month before the plant harvested. The results showed that the capacity of Cd in shoot of M. jalapa was 7.99μgpot-1 without any addition (CK4, M. jalapa in original soil without amendment). However, Cd capacity in shoot of M. jalapa was increased (p < 0.05) by 31.7%, 181.7%, and 107.4% in treatment of REGTA, RCA and REGTA + SA, respectively. As for the degradation of PAHs in soil, there was no significant decrease (p < 0.05) in the treatment of CK2 (original soil spiked with 0.9 SA without M. jalapa), CK3 (original soil spiked with 0.3 TW80 without M. jalapa), and CK4 compared to the control CK1 (original soil without M. jalapa and amendment). When amendments were added to soils with M. jalapa,the PAHs concentrations in soils significantly decreased (p < 0.05) by 21.7%, 23.8%, 27.0%, 19.8%, 21.8%, 31.2%, and 25.5% for the treatment of REDTA + SA, REDTA + T80, REGTA + SA, REGTA + T80, RCA + T80, RSA + T80 + EDTA, and RSA + T80 + CA, respectively. Basically, Cd capacity in shoot of M. jalapa was improved by chelators. PAHs degradation was caused by the existence of surfactants in rhizosphere of M. jalapa. But the roles of different chelators or surfactants were quite distinct. In short, the Cd capacity in the shoot and PAHs degradation in the rhizosphere of M. jalapa in the treatment of REGTA + SA were all significantly increased (p < 0.05), which was more practical for M. jalapa phytoremediating Cd-PAHs co-contaminated soil.

High PAH degradation and activity of degrading bacteria during alfalfa growth where a contrasted active community developed in comparison to unplanted soil.

PAH biodegradation in plant rhizosphere has been investigated in many studies, but the timescale of degradation and degrading bacteria activity was rarely considered. We explored the impact of plants on the temporal variability of PAH degradation, microbial abundance, activity, and bacterial community structure in a rhizotron experiment. A historically contaminated soil was spiked with PAHs, planted or not with alfalfa, over 22days with sampling once a week. In both conditions, most of the spiked PAHs were dissipated during the first week, conducting to polar polycyclic aromatic compound production and to decreased richness and diversity of bacterial communities. We showed a rapid impact of the rhizosphere on PAH degradation via the increased activity of PAH-degrading bacteria. After 12days, PAH degradation was significantly higher in the planted (100% degradation) than in unplanted (70%) soil. Gram-negative (Proteobacteria) PAH-dioxygenase genes and transcripts were higher in planted than unplanted soil and were correlated to the spiked PAH degradation. Conversely, Gram-positive (Actinobacteria) PAH-dioxygenase gene transcription was constant over time in both conditions. At 12days, plant growth favored the activity of many Gammaproteobacteria (Pseudomonadaceae, Stenotrophomonas, and Acinetobacter) while in unplanted soil Alphaproteobacteria (Sphingomonadaceae, Sphingobium, and Magnetospirillum) and Actinobacteria (Iamia, Geodermatophilaceae, and Solirubrobacterales) were more active.

Characteristic of Benzo[a]pyrene Anaerobic Degradation by Phenol Co-substrate and Microbial Communities from Two Types of Sludge

Benzo[a]pyrene (BaP) is a typical representative of PAHs in coking wastewater and priority-controlled pollutants in the coking industry; its response characteristics with microorganisms and the methods to promote its degradation are worth studying. On the other hand, because the inoculated sludge for the adjustment and operation of newly-constructed coking wastewater treatment plants comes from municipal sludge or other coking plants, currently, the study of the microbial properties of different sludges', sludge availability, and the conditions that influence these properties are lacking. On account of the above perspectives, an experiment to study and compare the durability of municipal sludge and coking sludge, and their ability to degrade BaP was carried out. An anaerobic reactor was selected for the experiment and anaerobic-activated sludges were collected from a coking wastewater processing unit and a municipal wastewater plant. Then, 10 mg·L-1 of BaP alone and BaP with phenol as a co-metabolic carbon source was added to the coking and municipal sludge samples, respectively, for comparison experiments to study the microbial degradation of BaP and its dynamics. Moreover, high-throughput sequencing technology was also used to analyze the changes in the microbial community structure before and after the degradation experiment. The results showed that:① Both sludges were capable of degrading BaP, but municipal sludge showed a higher degradation efficiency than coking sludge; ② Adding phenol as co-substrate promoted the biodegradation of BaP in both sludges. When BaP was the sole carbon source, the half-life of BaP in the two sludges was 155.41 d and 116.3 d respectively. After the addition of phenol, the half-life was reduced to 81.25 d and 38.44 d, respectively; ③ According to the analysis of the microbial community structure, the community composition in both sludges changed markedly. Moreover, the microbial community in the municipal sludge showed a more evident change than that of the coking sludge. In the coking sludge, the dominant bacteria community changed a little after acclimation, most of the observed bacteria were previously reported common PAH-degrading strains. In contrast, the dominant bacteria community in the municipal sludge varied greatly after acclimation, and the most abundant bacteria were not common PAH-degrading strains. In addition, some frequently reported PAHs-degrading bacteria such as Bacillus sp., Pseudomonas, Achromobacter, and Sphingomonas sp., were identified in both the sludges and were present in high abundance. The results indicated that municipal sludge utilized BaP more actively than coking sludge; this phenomenon can be explained by the fact that municipal sludge contained a higher diversity of microbes that were involved in the degradation of BaP. Furthermore, the presence of phenol promoted the degradation of PAHs like BaP. Therefore, we proposed that the PAHs in coking sludge discharge might be reduced by the addition phenol and municipal wastewater.

Evaluating the mycostimulation potential of select carbon amendments for the degradation of a model PAH by an ascomycete strain enriched from a superfund site.

Although ecological flexibility has been well documented in fungi, it remains unclear how this flexibility can be exploited for pollutant degradation, especially in the Ascomycota phylum. In this work, we assess three mycostimulation amendments for their ability to induce degradation in Trichoderma harzanium, a model fungus previously isolated from a Superfund site contaminated with polycyclic aromatic hydrocarbons. The amendments used in the present study were selected based on the documented ecological roles of ascomycetes. Chitin was selected to simulate the parasitic ecological role while cellulose and wood were selected to mimic bulk soil and wood saprobic conditions, respectively. Each amendment was tested in liquid basal medium in 0.1 and 1% (w/v) suspensions. Both chitin and cellulose amendments were shown to promote anthracene degradation in T. harzanium with the 0.1% chitin amendment resulting in over 90% removal of anthracene. None of the targets monitored for gene expression were found to be upregulated suggesting alternate pathways may be used in T. harzanium. Overall, our data suggest that mycostimulation amendments can be improved by understanding the ecological roles of indigenous fungi. However, further research is needed to better estimate specific amendment requirements for a broader group of target fungi and follow up studies are needed to determine whether the trends observed herein translate to more realistic soil systems.

Carbon nanomaterials differentially impact mineralization kinetics of phenanthrene and indigenous microbial communities in a natural soil

Previous reports on how carbon nanomaterials (CNMs) affect the biodegradation and mineralization of organic contaminants are mainly limited to pure culture studies, but little is known about the mineralization process by more complex and environmentally-relevant microbial communities. This study investigated the impact of fullerenes C60 and two multi-walled carbon nanotubes (outer diameter < 8 nm: M8; >50 nm: M50) at 300 and 3000 mg/kg on the mineralization kinetics of 14C-phenanthrene (18.5 mg/kg) by indigenous microorganisms in a natural soil for 120 days. Phenanthrene mineralization kinetics fitted well with the logistic growth equation regardless of the CNMs present (R2 = 0.965–0.985). The maximum mineralization rates and the total mineralization fraction were positively correlated with the initial phenanthrene bioavailability, assessed via β-HPCD extraction. Phenanthrene exposure induced significant responses of the catabolic gene biomarker nidA, fungi and bacteria communities by 275, 30, and 5 times, respectively, indicating a non-neglectable role of the fungal communities in phenanthrene mineralization. CNMs exerted a sorption- and level-dependent suppression (7.4–47.2%) on the total phenanthrene mineralization fractions at 120 d. Carbon nanotubes (300, 3000 mg/kg) caused significant adverse effects on the biomass of bacterial (47.8–60.7%), fungal (31.4–71.6%) and nidA-carrying degraders (25.7–59.9%) in the absence or presence of phenanthrene, which contributed to the inhibition of the total mineralization fractions at 120 d. Bacterial community structure was not significantly impacted by CNMs alone or co-exposure of CNM-phenanthrene. However, the fungal community showed a significant shift upon exposure to carbon nanotubes, especially M8, with the relative abundance of potential PAH degraders repressed (8.5–40.3%) at both levels of M8 tested. This corroborates the higher sensitivity of fungal communities. The findings from this study are important to inform how the released CNMs affect soil microbial communities that play a key role in the fate and remediation of organic contaminants in soil.

Different responses to soil petroleum contamination in monocultured and mixed plant systems

The role of plant composition should be considered during ecological risk assessment of soil petroleum contamination. To evaluate the influences of plant composition on phytotoxicity, petroleum degraders, and petroleum degradation, four treatments were arranged in the present study: unplanted, bristle grass only, alfalfa only, and bristle grass and alfalfa mixed planted in uncontaminated soil or petroleum contaminated soil (w/w, 1.0%). Petroleum contamination inhibited the growth of bristle grass and alfalfa significantly, and alfalfa growth inhibition was significantly alleviated when mixed planted with bristle grass (p < 0.05). MPN analysis indicated that the mixed plant treatment can gather the benefits of two species, and facilitate the development of alkane, total hydrocarbon and PAH degraders in contaminated soil, but not occur in uncontaminated soil. Compared with alfalfa only treatment, the degradation rates for total petroleum hydrocarbons (TPH) and aliphatic fraction were significantly increased in the mixed plant treatment (p < 0.05). However, the degradation of aromatic petroleum fraction was not received substantial improvement in the mixed plant treatment, despite containing an abundant PAH degraders. Overall, mixed plant cultivation had the significant influences on plant growth, microbial community and petroleum degradation in contaminated soils. The study provides valuable insights for vegetation restoration and remediation systems in petroleum contaminated sites of study area.

Effect of mixed soil microbiomes on pyrene removal and the response of the soil microorganisms

Mixed soil microbiomes were established by introducing aliquots of a paddy soil into a red soil. The new mixed microbiomes effectively metabolized high-molecular-weight polycyclic aromatic hydrocarbons (PAHs, pyrene) in the soil mixtures. The pyrene removal efficiencies were 19% and 98%, respectively, in the original red soil and the paddy soil. The pyrene removal effectiveness by the mixed microbial community was enhanced by increasing the amount of paddy soil inoculant and the pyrene removal rates were 93%, 58% and 27% in paddy soil/red soil mixtures of 1:1, 3:7 and 1:9 (w/w), respectively. Supplementation with sterile paddy soil and nutrients changed the soil environment but the pyrene removal efficiency was not enhanced, indicating that the microbial composition largely determined the extent of pyrene removal. Moreover, the pyrene removal rate was positively related to the pyrene dioxygenase gene (nidA) abundance. The greater the percentage of the paddy soil in the soil mixture the greater the similarity of the mixed microbiome to that of the original paddy soil itself. The community of the inoculated sterile paddy soil was similar to that of the red soil and the community diverged from those of the red soil and the paddy soil with increasing culture time. After culture for 42 days, some enriched genera were responsible for PAH degradation, notably Nevskia, Ralstonia, Gemmatimonas and Lysobacter, while some genera have no clear classification information or category name at the genus level, such as f__Acidobacteriaceae and o__JG30-KF-AS9. This study is very important in recognizing the role of natural soil in the formation of a mixed microbiome to stimulate the degradation of PAHs in a soil with low intrinsic PAH degradation capability.

Bioengineering for multiple PAHs degradation using process centric and data centric approaches

The study aims sequential bioengineering for multiple PAHs degradation using a process centric approach – response surface methodology (RSM) and a data centric approach – artificial neural networks (ANN). The study involves stepwise media optimization protocol for multiple PAHs degradation using newly isolated Stenotrophomonas maltophilia. RSM, a non linear model has predicted 94.70% degradation on 5th day with R2 value of 0.97. The analysis of desirability revealed the optimum value of the process conditions: NaCl – 27.55 g/L; NH4Cl- 0.28 g/L; Na2HPO4- 0.08 g/L, TAPSO- 1.74 g/L. Feed forward ANN, a linear model has predicted 95.94% degradation with R2 value of 0.99. The change in the magnitude of error functions viz. root mean square error (RMSE), mean absolute deviation (MAD) and mean absolute percentage error (MAPE) were low during ANN prediction as compared to RSM. Moreover, sensitivity analysis of both models also proves efficiency of the prediction capability and generalization of the data. Thus, for the very first time chemometrics study of medium components for multiple PAHs degradation offers constructive and powerful alternative to scientific community to design microcosm and mesocosm experiments.

Effect of lead, cadmium, and mercury co‐contaminants on biodegradation in PAH‐polluted soils

AbstractContamination of land by persistent organic pollutants has significant implications for human health and for future development potential. Bioremediation is an effective method for reducing the concentrations of such contaminants to below harmful levels, but the presence of co‐contaminants may hinder this process. Here, we present the results of a 40‐week microcosm study in which the biodegradation of 16 United States Environmental Protection Agency (USEPA) polycyclic aromatic hydrocarbons (PAHs; total: 2,166 mg kg−1) was followed in the presence of 3 different concentrations of cadmium (up to 620 mg kg−1) and lead (up to 782 mg kg−1) in a high organic matter soil. In the absence of metal treatment, 82% of PAHs were removed during the study period. Lead exerts a greater negative effect on total PAH removal than cadmium at low concentrations (approximately 100 mg kg−1) whilst cadmium exerts the greatest effect at higher concentrations (up to −27.7% reduction). Mercury, intended as the abiotic control (approximately 1,150 mg kg−1), exerts the greatest effect overall (−37%). Principal Component Analysis showed that PAH degradation was strongly associated with soil respiration rate, biomass content, and Ecoplate Average Well Colour Development. During the initial phase of the experiment, reduced microbial diversity was associated with increased PAH removal, consistent with literature observations for other organic contaminants, though this association was reversed after Week 12. Degradation of higher molecular weight PAHs showed the greatest sensitivity to the health of the microbial community. The effect of metal treatments on biotic parameters in microcosms without PAH amendment is also presented.

Half-lives of PAHs and temporal microbiota changes in commonly used urban landscaping materials.

BackgroundPolycyclic aromatic hydrocarbons (PAHs) accumulate in urban soils, and PAH contamination can change soil microbial community composition. Environmental microbiota is associated with human commensal microbiota, immune system and health. Therefore, studies investigating the degradation of PAHs, and the consequences of soil pollution on microbial communities in urban landscaping materials, are crucial.MethodsFour landscaping materials (organic matter 1, 2, 13 and 56%) were contaminated with PAHs commonly found at urban sites (phenanthrene, fluoranthene, pyrene, chrysene and benzo(b)fluoranthene) in PAH concentrations that reflect urban soils in Finland (2.4 µg g -1 soil dry weight). PAHs were analyzed initially and after 2, 4, 8 and 12 weeks by gas chromatography-mass spectrometry. Half-lives of PAHs were determined based on 12-weeks degradation. Bacterial communities were analyzed at 1 and 12 weeks after contamination using Illumina MiSeq 16S rRNA gene metabarcoding.ResultsHalf-lives ranged from 1.5 to 4.4 weeks for PAHs with relatively low molecular weights (phenanthrene, fluoranthene and pyrene) in landscaping materials containing 1–2% organic matter. In contrast, in materials containing 13% and 56% organic matter, the half-lives ranged from 2.5 to 52 weeks. Shorter half-lives of phenanthrene and fluoranthene were thus associated with low organic matter content. The half-life of pyrene was inversely related to the relative abundance of Beta-, Delta- and Gammaproteobacteria, and diversity of Bacteroidetes and Betaprotebacteria. Compounds with higher molecular weights followed compound-specific patterns. Benzo(b)fluoranthene was resistant to degradation and half-life of chrysene was shorter when the relative abundance of Betaproteobacteria was high. Temporal microbiota changes involved increase in the relative abundance of Deltaproteobacteria and decrease in genera Flavobacterium and Rhodanobacter. Exposure to PAHs seems to adjust microbial community composition, particularly within class Beta- and Deltaproteobacteria.ConclusionsIn this study, PAH degradation depended on the organic matter content and bacterial community composition of landscaping materials. Contamination seems to alter bacterial community composition in landscaping materials depending on material type. This alteration includes changes in bacterial phyla associated with human health and immune system. This may open new possibilities for managing urban environments by careful selection of landscaping materials, to benefit health and wellbeing.

First Characterization of PAH-degrading bacteria from Río de la Plata and high-resolution melting: an encouraging step toward bioremediation

ABSTRACTThe Río de la Plata, one of the most important estuarine environments in South America that sustains valuable fisheries, is affected by PAH contamination associated with oil industry and port activities. A total of 95 bacteria with potential to degrade phenanthrene were obtained from water samples using traditional culture methods. PCR-RFLP analysis of 16S rDNA partial fragments was used as a screening tool for reducing the number of isolates during diversity studies, obtaining 42 strains with different fingerprint patterns. Phylogenetic analysis indicated that they were affiliated to 19 different genera of Gamma- and Alpha-Proteobacteria, and Actinobacteria. Some of them showed an efficient phenanthrene degradation by HPLC (between 83% and 97%) and surfactant production (between 40% and 55%). They could be an alternative for microbial selection in the degradation of PAHs in this estuarine system. In order to detect and monitor PAH-degrading bacteria in this highly productive area, rDNA amplicons of the 33 isolates, produced by PCR real time, were tested by the high-resolution melting (HRM) technique. After analyzing the generated melting curves, it was possible to accurately distinguish nine patterns corresponding to eight different genera. HRM analysis allowed a differentiation at the species level for genera Pseudomonas, Halomonas and Vibrio. The implementation of this method as a fast and sensitive scanning approach to identify PAH-degrading bacteria, avoiding the sequencing step, would mean an advance in bioremediation technologies.

The Emergence of Different Functionally Equivalent PAH Degrading Microbial Communities from a Single Soil in Liquid PAH Enrichment Cultures and Soil Microcosms Receiving PAHs with and without Bioaugmentation.

Polycyclic aromatic hydrocarbon (PAHs) are common soil contaminants of concern due to their toxicity toward plants, animals and microorganisms. The use of indigenous or added microbes (bioaugmentation) is commonly used for bioremediation of PAHs. In this work, the biodegradation rates and changes in the bacterial community structure were evaluated. The enrichment culture was useful for unambiguously identifying members of the soil bacterial community associated with PAH degradation and yielded a low diversity community. No significant difference in the rate of PAH degradation was observed between the microcosm receiving only PAHs or PAHs and bioaugmentation. Moreover, identical matches to the bioaugmentation inoculum were only observed at the initial stages of PAH degradation on day 8. After 22 days of incubation, the substantial degradation of all PAHs had occurred in both microcosms and the PAH contaminated soil had statistically significant increases in Alphaproteobacteria. There were also increases in Betaproteobacteria. In contrast, the PAH contaminated and bioaugmented soil was not enriched in PAH degrading Proteobacteria genera and, instead, an increase from 1.6% to 8% of the population occurred in the phylum Bacteroidetes class Flavobacteria, with Flavobacterium being the only identified genus. In addition, the newly discovered genus Ohtaekwangia increased from 0% to 3.2% of the total clones. These results indicate that the same soil microbial community can give rise to different PAH degrading consortia that are equally effective in PAH degradation efficiency. Moreover, these results suggest that the lack of efficacy of bioaugmentation in soils can be attributed to a lack of persistence of the introduced microbes, yet nonetheless may alter the microbial community that arises in response to PAH contamination in unexpected ways.

Ligninolytic basidiomycetes as promising organisms for the mycoremediation of PAH-contaminated Environments

Primary screening of ligninolytic fungi belonging to wood- and soil-inhabiting basidiomycetes revealed their ability to degrade three-ringed PAHs with formation of quinone metabolites at the first stage. The degradative activity was both species and strain specific, and some differences in the “chances” for the formed quinones were found. They were the main end metabolites in the degradation of PAHs by Stropharia rugosoannulata and Agaricus bisporus. During PAH degradation by strains of Trametes versicolor, Pleurotus ostreatus, Schizophyllum commune, and Bjerkandera adusta similar metabolites were detected during the cultivation, but they were utilized further. The results supported the hypothesis that the degree of PAH degradation may depend on the composition of the extracellular ligninolytic complex of the fungi: in the presence of a single ligninolytic enzyme, laccase, the accumulation of quinone metabolites takes place; their further utilization is possible with the participation of ligninolytic peroxidases. The data obtained showed the necessity not only to identify the metabolites formed, but also to study the activity of the basic ligninolytic enzymes. It is important for the correct selection of fungal strains for mycoremediation.

Optimization parameters for Mycobacteria confluentis biodegradation of PAHs

In this study, the effect of process parameters (incubation period, temperature, initial pH-value, concentration of PAHs in the medium, and bacterial inoculum size) on the biodegradation of PAHs using Mycobacteria confluentis was studied using One-Factor-At-a-Time (OFAT) method. From the results of the study, it was observed that the studied parameters had significant effects on the degradation process. The capability of Mycobacteria confluentis on the degradation of PAHs was found to be maximum when the initial pH of the PAH was 7, temperature 40 °, PAH concentration of 50 μL, bacterial concentration of 7.5 mL, and incubated for 3 to 5 days. This condition gave a PAH degradation percentage of 40 to 50 %, showing a similarity to most previous studies where the maximum percentage of degradation has been around 40 to 50 %. This study, therefore, concludes that Mycobacteria confluentis is a good PAHs degrader which can be of significant important in the management of oil polluted fields and environments.

Biodegradation of Polyaromatic Hydrocarbons by Acclimatized Mixed Culture Using Shake Flask and Roller Bioreactors

The ability of acclimatized mixed culture from sewage waste sludge was tested to biodegrade (PAHs): naphthalene and phenanthrene each with a concentration of 300 mg/L. Sewage sludge was selected as an inexpensive source of mixed culture of microorganisms, usually available in large quantities in wastewater treatment plants. Two types of reactors were employed in the investigation: shake flask and roller bioreactors. Complete biodegradation of naphthalene and phenanthrene was achieved in the shake flask bioreactor after 13 and 14 days of treatment, respectively. The corresponding durations in the roller bioreactor were 11 and 12 days. The obtained results show that the said culture is capable of consuming PAHs as energy and carbon source and have a promising application in bioremediation of PAH contaminated environments. The biodegradation of naphthalene was enhanced when using the roller bioreactor compared to its biodegradation in the shake flask bioreactor. The microorganisms’ specific growth rate was raised from 0.014 to 0.022 h-1 due to the enhanced mixing in the roller bioreactor. No enhancement was observed for phenanthrene biodegradation when using the roller bioreactor: the microorganisms’ specific growth rate was equal to 0.016 h-1 for the shake flask bioreactor compared to 0.012 h-1 for the roller bioreactor. Logistic models were employed for the description of the microorganisms’ growth and the PAHs degradation in both shake flask and roller bioreactor. Additionally, second order inhibition model was used to describe the possible inhibitions. The results obtained from the models well-matched the biodegradation experimental data with R2 of more than 97%.

Applying ultrasonic in the PAHs degradation in sewage sludge

Applying ultrasonic in the PAHs degradation in sewage sludge

Comparison of the PAHs degradation effectiveness using CaO2 or H2O2 under the photo-Fenton reaction

Comparison of the PAHs degradation effectiveness using CaO2 or H2O2 under the photo-Fenton reaction