Analysis of bacterial degradation pathways for long-chain alkylphenols involving phenol hydroxylase, alkylphenol monooxygenase and catechol dioxygenase genes

Overview of enhancing biological treatment of coal chemical wastewater: New strategies and future directions

Coal chemical wastewater (CCW) is a type of refractory industrial wastewater, and its treatment has become the main bottleneck restricting the sustainable development of novel coal chemical industry. Biological treatment is considered as an economical, effective and environmentally friendly technology for CCW treatment. However, conventional biological process is difficult to achieve the efficient removal of refractory organics because of CCW with the characteristics of composition complexity and high toxicity. Therefore, seeking the novel enhancement strategy appears to be a favorable solution for enhancing biological treatment efficiency of CCW. This review focuses on presenting a comprehensive picture about the exogenous enhancement strategies for CCW biological treatment. The performance and potential application of exogenous enhancement strategies, including co-metabolic substrate enhancement, biofilm filler enhancement, adsorption material enhancement and conductive mediator enhancement, were expounded. Meanwhile, the enhancing mechanisms of different strategies were comprehensively discussed from a biological perspective. Furthermore, the prospects of enhancement strategies based on the engineering performance, economic cost and environmental impact (3E) evaluation were introduced. And novel enhancement strategy based on "low carbon emissions", "resource recycling" and "water environment security" in the context of carbon neutrality was proposed. Taken together, this review provides technical reference and new direction to facilitate the regulation and optimization of typical industrial wastewater biological treatment.

Identification of key degraders for controlling toxicity risks of disguised toxic pollutants with division of labor mechanisms in activated sludge microbiomes: Using nonylphenol ethoxylate as an example

Efficient management of disguised toxic pollutants (DTPs), which can undergo microbial degradation and convert into more toxic substances, necessitates the collaboration of diverse microbial populations in wastewater treatment plants. However, the identification of key bacterial degraders capable of controlling the toxicity risks of DTPs through division of labor mechanisms in activated sludge microbiomes has received limited attention. In this study, we investigated the key degraders capable of controlling the risk of estrogenicity associated with nonylphenol ethoxylate (NPEO), a representative DTP, in textile activated sludge microbiomes. The results of our batch experiments revealed that the transformation of NPEO into NP and subsequent NP degradation were the rate-limiting processes for controlling the risk of estrogenicity, resulting in an inverted V-shaped curve of estrogenicity in water samples during the biodegradation of NPEO by textile activated sludge. By utilizing enrichment sludge microbiomes treated with NPEO or NP as the sole carbon and energy source, a total of 15 bacterial degraders, including Sphingbium, Pseudomonas, Dokdonella, Comamonas, and Hyphomicrobium, were identified as capable of participating in these processes, Among them, Sphingobium and Pseudomonas were the two key degraders that could cooperatively interact in the degradation of NPEO with division of labor mechanisms. Co-culturing Sphingobium and Pseudomonas isolates exhibited a synergistic effect in degrading NPEO and reducing estrogenicity. Our study underscores the potential of the identified functional bacteria for controlling estrogenicity associated with NPEO and provides a methodological framework for identifying key cooperators engaged in labor division, contributing to the management of risks associated with DTPs by leveraging intrinsic microbial metabolic interactions.

Biodegradation of phenol by Candida tropicalis sp.: Kinetics, identification of putative genes and reconstruction of catabolic pathways by genomic and transcriptomic characteristics

Candida tropicalis sp. was isolated with predominant biodegradation capability to phenol compounds, even with high concentration or in acid environment. The biodegradation of phenol was evaluated at the following concentrations 10-1750 mg L^-1, the strain exhibited well biodegradation efficiency. The maximum specific growth rate was 0.660 h^-1 and the specific biodegradation rates was 0.47 mg (phenol) [(mg (VSS) h]^-1. Differentially expressed genes were screened out, and results revealed a complete process of energy and carbon metabolism. The genes' arrangements and phylogenetic information showed the unique genetic characteristics of the strain. Catabolic pathways were reconstructed and some key phenol-degrading genes were obviously upregulated, including pheA, catA, OXCT and fadA. A notable detail that CMBL encoding carboxymethylenebutenolidase was speculated to be involved in a shortened pathway of phenol biodegradation, thereby contributing to the reconstruction of the novel phenol catabolic pathway through the hydrolases of dienelactone. Finally, key enzymes were verified by the analysis of specific activity.

Pseudomonas in environmental bioremediation of hydrocarbons and phenolic compounds- key catabolic degradation enzymes and new analytical platforms for comprehensive investigation

Pollution of the environment with petroleum hydrocarbons and phenolic compounds is one of the biggest problems in the age of industrialization and high technology. Species of the genus Pseudomonas, present in almost all hydrocarbon-contaminated areas, play a particular role in biodegradation of these xenobiotics, as the genus has the potential to decompose various hydrocarbons and phenolic compounds, using them as its only source of carbon. Plasticity of carbon metabolism is one of the adaptive strategies used by Pseudomonas to survive exposure to toxic organic compounds, so a good knowledge of its mechanisms of degradation enables the development of new strategies for the treatment of pollutants in the environment. The capacity of microorganisms to metabolize aromatic compounds has contributed to the evolutionally conserved oxygenases. Regardless of the differences in structure and complexity between mono- and polycyclic aromatic hydrocarbons, all these compounds are thermodynamically stable and chemically inert, so for their decomposition, ring activation by oxygenases is crucial. Genus Pseudomonas uses several upper and lower metabolic pathways to transform and degrade hydrocarbons, phenolic compounds, and petroleum hydrocarbons. Data obtained from newly developed omics analytical platforms have enormous potential not only to facilitate our understanding of processes at the molecular level but also enable us to instigate and monitor complex biodegradations by Pseudomonas. Biotechnological application of aromatic metabolic pathways in Pseudomonas to bioremediation of environments polluted with crude oil, biovalorization of lignin for production of bioplastics, biofuel, and bio-based chemicals, as well as Pseudomonas-assisted phytoremediation are also considered.

Isolation and optimization of a glyphosate-degrading Rhodococcus soli G41 for bioremediation

A widely used herbicide for controlling weeds, glyphosate, is causing environmental pollution. It is necessary to remove it from environment using a cost-effective and eco-friendly method. The aims of this study were to isolate glyphosate-degrading bacteria and to optimize their degradative conditions required for bioremediation. Sixteen bacterial strains were isolated through enrichment and one strain, Rhodococcus soli G41, demonstrated a high removal rate of glyphosate than other strains. Response surface methodology was employed to optimize distinct environmental factors on glyphosate degradation of G41 strain. The optimal conditions for the maximum glyphosate degradation were found to have the NH4Cl concentration of 0.663% and glyphosate concentration of 0.115%, resulting in a maximum degradation of 42.7% after 7 days. Bioremediation analysis showed 47.1% and 40% of glyphosate in unsterile soil and sterile soil was removed by G41 strain after 14 days, respectively. The presence of soxB gene in G41 strain indicates that the glyphosate is degraded via the eco-friendly sarcosine pathway. The results indicated that G41 strain has the potential to serve as an in-situ candidate for bioremediation of glyphosate polluted environments.

A multicomponent THF hydroxylase initiates tetrahydrofuran degradation in Cupriavidus metallidurans ZM02

Tetrahydrofuran (THF) has been recognized as a water contaminant because of its human carcinogenicity, extensive use, and widespread distribution. Previously reported multicomponent monooxygenases (MOs) involved in THF degradation were highly conserved, and all of them were from Gram-positive bacteria. In this study, a novel THF-degrading gene cluster (dmpKLMNOP) encoding THF hydroxylase was identified on the chromosome of a newly isolated Gram-negative THF-degrading bacterium, Cupriavidus metallidurans ZM02, and functionally characterized. Transcriptome sequencing and RT-qPCR demonstrated that the expression of dmpKLMNOP was upregulated during the growth of strain ZM02 on THF or phenol. The deletion of oxygenase alpha or beta subunit or the reductase component disrupted the degradation of THF but did not affect the utilization of its hydroxylated product 2-hydroxytetrahydrofuran. Cupriavidus pinatubonensis JMP134 heterologously expressing dmpKLMNOP from strain ZM02 could grow on THF, indicating that the THF hydroxylase Dmp_ZM02KLMNOP is responsible for the initial degradation of THF. Furthermore, the THF and phenol oxidation activities of crude enzyme extracts were detected, and the highest THF and phenol catalytic activities were 1.38±0.24 μmol min^-1 mg^-1 and 1.77±0.37 μmol min^-1 mg^-1, respectively, with the addition of NADPH and Fe²⁺. The characterization of THF hydroxylase associated with THF degradation enriches our understanding of THF-degrading gene diversity and provides a novel potential enzyme for the bioremediation of THF-containing pollutants. IMPORTANCE Multicomponent MOs catalyzing the initial hydroxylation of THF are vital rate-limiting enzymes in the THF degradation pathway. Previous studies of THF degradation gene clusters have focused on Gram-positive bacteria, and the molecular mechanism of THF degradation in Gram-negative bacteria has rarely been reported. In this study, a novel THF hydroxylase encoded by dmpKLMNOP in strain ZM02 was identified to be involved in both THF and phenol degradation. Our findings provide new insights into the THF-degrading gene cluster and enzymes in Gram-negative bacteria.

Biodegradation Potential and Putative Catabolic Genes of Culturable Bacteria from an Alpine Deciduous Forest Site

Microbiota from Alpine forest soils are key players in carbon cycling, which can be greatly affected by climate change. The aim of this study was to evaluate the degradation potential of culturable bacterial strains isolated from an alpine deciduous forest site. Fifty-five strains were studied with regard to their phylogenetic position, growth temperature range and degradation potential for organic compounds (microtiter scale screening for lignin sulfonic acid, catechol, phenol, bisphenol A) at low (5 °C) and moderate (20 °C) temperature. Additionally, the presence of putative catabolic genes (catechol-1,2-dioxygenase, multicomponent phenol hydroxylase, protocatechuate-3,4-dioxygenase) involved in the degradation of these organic compounds was determined through PCR. The results show the importance of the Proteobacteria phylum as its representatives did show good capabilities for biodegradation and good growth at -5 °C. Overall, 82% of strains were able to use at least one of the tested organic compounds as their sole carbon source. The presence of putative catabolic genes could be shown over a broad range of strains and in relation to their degradation abilities. Subsequently performed gene sequencing indicated horizontal gene transfer for catechol-1,2-dioxygenase and protocatechuate-3,4-dioxygenase. The results show the great benefit of combining molecular and culture-based techniques.

Occurrence, potential ecological risks, and degradation of endocrine disrupter, nonylphenol, from the aqueous environment

Nonylphenol (NP) is considered a potential endocrine-disrupting chemical affecting humans and the environment. Due to widespread occurrence in the aquatic environment and neuro-, immuno, reproductive, and estrogenic effects, nonylphenol calls for considerable attention from the scientific community, researchers, government officials, and the public. It can persist in the environment, especially soil, for a long duration because of its high hydrophobic nature. Nonylphenol is incorporated into the water matrices via agricultural run-off, wastewater effluents, agricultural sources, and groundwater leakage from the soil. In this regard, assessment of the source, fate, toxic effect, and removal of nonylphenol seems a high-priority concern. Remediation of nonylphenol is possible through physicochemical and microbial methods. Microbial methods are widely used due to ecofriendly in nature. The microbial strains of the genera, Sphingomonas, Sphingobium, Pseudomonas, Pseudoxanthomonas, Thauera, Novosphingonium, Bacillus, Stenotrophomonas, Clostridium, Arthrobacter, Acidovorax, Maricurvus, Rhizobium, Corynebacterium, Rhodococcus, Burkholderia, Acinetobacter, Aspergillus, Pleurotus, Trametes, Clavariopsis, Candida, Phanerochaete, Bjerkandera, Mucor, Fusarium and Metarhizium have been reported for their potential role in the degradation of NP via its metabolic pathway. This study outlines the recent information on the occurrence, origin, and potential ecological and human-related risks of nonylphenol. The current development in the removal of nonylphenol from the environment using different methods is discussed. Despite the significant importance of nonylphenol and its effects on the environment, the number of studies in this area is limited. This review gives an in-depth understanding of NP occurrence, fate, toxicity, and remediation from the environments.

Alkylphenols and Chlorophenols Remediation in Vertical Flow Constructed Wetlands: Removal Efficiency and Microbial Community Response

This study aims to investigate the effect of two different groups of phenolic compounds (the alkylphenols nonylphenol (NP) and octylphenol (OP), and the chlorophenol pentachlorophenol (PCP)) on constructed wetlands (CWs) performance, including on organic matter, nutrients and contaminants removal efficiency, and on microbial community structure in the plant bed substrate. CWs were assembled at lab scale simulating a vertical flow configuration and irrigated along eight weeks with Ribeira de Joane (an urban stream) water not doped (control) or doped with a mixture of NP and OP or with PCP (at a 100 μg·L−1 concentration each). The presence of the phenolic contaminants did not interfere in the removal of organic matter or nutrients in CWs in the long term. Removals of NP and OP were >99%, whereas PCP removals varied between 87% and 98%, mainly due to biodegradation. Microbial richness, diversity and dominance in CWs substrate were generally not affected by phenolic compounds, with only PCP decreasing diversity. Microbial community structure, however, showed that there was an adaptation of the microbial community to the presence of each contaminant, with several specialist genera being enriched following exposure. The three more abundant specialist genera were Methylotenera and Methylophilus (methylophilaceae family) and Hyphomicrobium (hyphomicrobiaceae family) when the systems were exposed to a mixture of NP and OP. When exposed to PCP, the three more abundant genera were Denitromonas (Rhodocyclaceae family), Xenococcus_PCC_7305 (Xenococcaceae family) and Rhodocyclaceae_uncultured (Rhodocyclaceae family). To increase CWs efficiency in the elimination of phenolic compounds, namely PCP which was not totally removed, strategies to stimulate (namely biostimulation) or increase (namely bioaugmentation) the presence of these bacteria should be explore. This study clearly shows the potential of vertical flow CWs for the removal of phenolic compounds, a still little explored subject, contributing to promote the use of CWs as nature-based solutions to remediate water contaminated with different families of persistent and/or emergent contaminants.

Draft Genome Sequence of Phenol-Degrading Variovorax boronicumulans Strain c24

We report the draft genome sequence of Variovorax boronicumulans strain c24, which was isolated from a soil-inoculated chemostat culture amended with phenol as a sole carbon and energy source. The genome data will provide insights into phenol and other xenobiotic compound degradation mechanisms for bioremediation applications.

We report the draft genome sequence of Variovorax boronicumulans strain c24, which was isolated from a soil-inoculated chemostat culture amended with phenol as a sole carbon and energy source. The genome data will provide insights into phenol and other xenobiotic compound degradation mechanisms for bioremediation applications.

Kinetics of Phenol Biodegradation by Heavy Metal Tolerant Rhizobacteria Glutamicibacter nicotianae MSSRFPD35 From Distillery Effluent Contaminated Soils

Biodegradation of phenol using bacteria is recognized as an efficient, environmentally friendly and cost-effective approach for reducing phenol pollutants compared to the current conventional physicochemical processes adopted. A potential phenol degrading bacterial strain Glutamicibacter nicotianae MSSRFPD35 was isolated and identified from Canna indica rhizosphere grown in distillery effluent contaminated sites. It showed high phenol degrading efficiency up to 1117 mg L^–1 within 60 h by the secretion of catechol 1,2-dioxygenase via ortho intradial pathway. The strain MSSRFPD35 possess both the catechol 1,2 dioxygenase and catechol 2,3 dioxygenase coding genes that drive the ortho and meta pathways, but the enzymatic assay revealed that the strain cleaves catechol via ortho pathway. Haldane’s kinetic method was well fit to exponential growth data and the following kinetic parameter was obtained: μ^∗ = 0.574 h^–1, K_i = 268.1, K_s = 20.29 mg L^–1. The true μ_max and S_m were calculated as 0.37 h^–1 and 73.76 mg L^–1, respectively. The Haldane’s constant values were similar to earlier studies and healthy fitness depicted in correlation coefficient value R² of 0.98. Phenol degrading kinetic’s was predicted using Haldane’s model as q_max 0.983, K_i′ 517.5 and K_s′ 9.152. Further, MSSRFPD35 was capable of utilizing different monocyclic and polycyclic aromatic hydrocarbons and to degrade phenol in the presence of different heavy metals. This study for the first time reports high phenol degrading efficiency of G. nicotianae MSSRFPD35 in the presence of toxic heavy metals. Thus, the strain G. nicotianae MSSRFPD35 can be exploited for the bioremediation of phenol and its derivatives polluted environments, co-contaminated with heavy metals.

Degradation and transformation of nitrated nonylphenol isomers in activated sludge under nitrifying and heterotrophic conditions

Nitrated nonylphenols (2-nitro-nonylphenols, NNPs) are metabolites of the endocrine-disrupter nonylphenols (NPs). While they have been detected in the environment, their fate in activated sludge has yet to be determined. In this study, we used synthesized NNP isomers and a ¹⁴C-tracer technique to study the degradation and transformation of four NNP isomers (NNP₁₁₁, NNP₁₁₂, NNP₃₈, and NNP₆₅) in nitrifying activated sludge (NAS) and heterotrophic bacteria-enhanced activated sludge (HAS). Our results showed that the degradation of NNPs in both NAS and HAS was isomer-specific. The half-lives of the NNPs decreased in the order: NNP₁₁₁ > NNP₁₁₂ > NNP₃₈ > NNP₆₅. After 36 days of incubation, 9.48 % and 4.01 % of the ¹⁴C-NNP₁₁₁ was mineralized in NAS and HAS, respectively. In addition to mineralization, five metabolites of NNPs containing hydroxyl, carbonyl, and carboxyl substituents on the alkyl chains were formed in NAS but not in HAS. The transformation of NNPs differed in NAS and HAS, mainly due to the differences in their microbial communities and the activities thereof in NAS and HAS. This is the first study of the isomer-specific fate of NNP isomers in activated sludge. Future studies should assess the toxicity, stability and potential risks of NNP metabolites in the environment.

Removal of nonylphenol polyethoxylates by adsorption on polyurethane foam and biodegradation using immobilized Trametes versicolor

Nonylphenol polyethoxylates (NPEOs) are banned in EU due to their endocrine disrupting properties. In a proof of concept study including continuous reactor lab-scale experiments, polyurethane foam (PUF)-immobilized Trametes versicolor was used to reduce the concentration levels of these compounds in an acidic nutrient solution over an 18-day period. Biodegradation and adsorption were identified as the major removal principles. A 90% removal was achieved by solely biodegradation in an experimental setup in which steady state conditions occurred, including NPEO-saturated glass and PUF surfaces. Biotransformation products containing mono- and di-ethoxylated nonylphenol, nonylphenol (NP1EO, NP2EO, NP) and nonylphenol polyethoxy carboxylates (NPECs) were tentatively identified. The maximum static NPEO adsorption capacity of PUF (determined with Erlenmeyer flask experiment) was calculated to 106 mg g^-1, and the adsorption was described by the Langmuir isotherm equation. The corresponding maximum dynamic adsorption capacity (determined by continuous reactor experiment) was 100 mg g^-1. These findings show that PUF is an excellent adsorbent to NPEOs. Therefore, PUF can either be used as a stand-alone adsorbent to NPEOs or as an immobilizing agent for Trametes versicolor through which a highly efficient biodegradation of these potentially harmful compounds can be achieved. The findings can be of importance in the search for alternative methods to remove NPEOs in process effluents.

Biodegradation of the endocrine disrupter 4-t-octylphenol by the non-ligninolytic fungus Fusarium falciforme RRK20: Process optimization, estrogenicity assessment, metabolite identification and proposed pathways

4-t-octylphenol (4-t-OP), a well-known endocrine disrupting compound, is frequently found in various environmental compartments at levels that may cause adverse effects to the ecosystem and public health. To date, most of the studies that investigate microbial transformations of 4-t-OP have focused on the process mediated by bacteria, ligninolytic fungi, or microbial consortia. There is no report on the complete degradation mechanism of 4-t-OP by non-ligninolytic fungi. In this study, we conducted laboratory experiments to explore and characterize the non-ligninolytic fungal strain Fusarium falciforme RRK20 to degrade 4-t-OP. Using the response surface methodology, the initial biomass concentration and temperature were the factors identified to be more influential on the efficiency of the biodegradation process as compared with pH. Under the optimized conditions (i.e., 28 °C, pH 6.5 with an initial inoculum density of 0.6 g L^-1), 25 mg L^-1 4-t-OP served as sole carbon source was completely depleted within a 14-d incubation; addition of low dosage of glucose was shown to significantly accelerate 4-t-OP degradation. The yeast estrogenic screening assay further confirmed the loss of estrogenic activity during the biodegradation process, though a longer incubation period was required for complete removal of estrogenicity. Metabolites identified by LC-MS/MS revealed that strain RRK20 might degrade 4-t-OP as sole energy source via alkyl chain oxidation and aromatic ring hydroxylation pathways. Together, these results not only suggest the potential use of non-ligninolytic fungi like strain RRK20 in remediation of 4-t-OP contaminated environments but may also improve our understanding of the environmental fate of 4-t-OP.

Characterization of a pH-Tolerant Strain Cobetia sp. SASS1 and Its Phenol Degradation Performance Under Salinity Condition

Biological treatment of complex saline phenolic wastewater remains a great challenge due to the low activity of bacterial populations under stressful conditions. Acid mine drainage (AMD) as a typically extreme environment, shaped unique AMD microbial communities. Microorganisms survived in the AMD environment have evolved various mechanisms of resistance to low pH, high salinity and toxic heavy metals. The primary goal of this work was to determine whether a strain isolated from an AMD could degrade phenol under stressful conditions such as low pH, high salinity and heavy metals. The results suggested that the strain Cobetia sp. SASS1 isolated from AMD presented different physiological characteristics in comparison with five most closely related species. SASS1 can efficiently degrade phenol at wide ranges of pH (3.0-9.0) and NaCl concentration (0-40 g/L), as well as the existence of Cu2+ and Mn2+. Specifically, the SASS1 could completely degrade 1500 mg/L phenol in 80 h at 10 g/L NaCl. Meanwhile, mineralization of phenol was achieved with complete degradation of 900 mg/L phenol and simultaneously COD decreasing from 2239 mg/L to 181.6 mg/L in 36 h. Based on biodegradation metabolites identification and enzyme activities analysis, both ortho-cleavage pathway and benzoic acid pathway for phenol degradation were proposed. These findings suggested that SASS1 was an efficient phenol degrader under salinity and acidic conditions, and could be considered as key population for bioremediation of industrial phenolic wastewaters under stressful conditions.

Construction of an Escherichia coli strain to degrade phenol completely with two modified metabolic modules

Phenol is a common water pollutant because of its broad industrial applications. Biological method is a promising alternative to conventional physical and chemical methods for removing this toxic pollutant from the environment. In this study, two metabolic modules were introduced into Escherichia coli, the widely used host for various genetic manipulations, to elucidate the metabolic capacity of E. coli for phenol degradation. The first module catalysed the conversion of phenol to catechol, whereas the second module cleaved catechol into the three carboxylic acid circulating intermediates by the ortho-cleavage pathway. Phenol was completely degraded and imported into the tricarboxylic acid cycle by the engineered bacteria. Proteomics analysis showed that all genes in the phenol degradation pathway were over-expressed and affected cell division and energy metabolism of the host cells. Phenol in coking wastewater was degraded powerfully by BL-phe/cat. The engineered E. coli can improve the removal rate and shorten the processing time for phenol removal and has considerable potential in the treatment of toxic and harmful pollutants.

Bio-Fenton reaction involved in the cleavage of the ethoxylate chain of nonionic surfactants by dihydrolipoamide dehydrogenase from Pseudomonas nitroreducens TX1

Bacteria in the environment play a major role in the degradation of widely used man-made recalcitrant organic compounds. Pseudomonas nitroreducens TX1 is of special interest because of its high efficiency to remove nonionic ethoxylated surfactants. In this study, a novel approach was demonstrated by a bacterial enzyme involved in the formation of radicals to attack ethoxylated surfactants. The dihydrolipoamide dehydrogenase was purified from the crude extract of strain TX1 by using octylphenol polyethoxylate (OPEO_n) as substrate. The extent of removal of OPEOs during the degradation process was conducted by purified recombinant enzyme from E. coli BL21 (DE3) in the presence of the excess of metal mixtures (Mn²⁺, Mg²⁺, Zn²⁺, and Cu²⁺). The metabolites and the degradation rates were analyzed and determined by liquid chromatography-mass spectrometry. The enzyme was demonstrated to form Fenton reagent in the presence of an excess of metals. Under this in vitro condition, it was shown to be able to shorten the ethoxylate chains of OPEO_n. After 2 hours of reaction, the products obtained from the degradation experiment revealed a prominent ion peak at m/z = 493.3, namely the ethoxylate chain unit is 6 (OPEO₆) compared to OPEO₉ (m/z = 625.3), the main undegraded surfactant in the no enzyme control. It revealed that the concentration of OPEO₁₅ and OPEO₉ decreased by 90% and 40% after 4 hours, respectively. The disappearance rates for the OPEO_n homologs correlated to the length of the exothylate chains, suggesting it is not a specific enzymatic reaction which cleaves one unit by unit from the end of the ethoxylate chain. The results indicate the diverse and novel strategy by bacteria to catabolize organic compounds by using existing housekeeping enzyme(s).

Simultaneous enhancement of nonylphenol biodegradation and short-chain fatty acids production in waste activated sludge under acidogenic conditions

Nonylphenol (NP) biodegradation in waste activated sludge (WAS) under anaerobic conditions is usually slow, and no information on NP biodegradation under acidogenic conditions is currently available. In this study, the simultaneous enhancement of NP biodegradation and short-chain fatty acids (SCFAs) accumulation in a WAS fermentation system under acidogenic conditions was accomplished by controlling pH 10 and adding sodium lauryl sulfate (SLS). The biodegradation efficiency of NP was found to be 55.5% within 8 d under acidogenic conditions, much higher than that in the control (24.6%). Meanwhile, the concentration of SCFAs under the same conditions for NP biodegradation was increased from 2234 mg COD/L (control) to 4691 mg COD/L (at pH 10 with SLS). Mechanism study revealed that the abundances of both NP-degrading microorganisms and acidogenic bacteria increased under acidogenic conditions. Altering the enzymatic activity and the quantity of functional genes in the acidogenic fermentation system were beneficial to NP biodegradation and SCFAs accumulation. Furthermore, organic substrates available for uptake by NP-degrading and acidogenic bacteria, i.e. NP, protein and carbohydrate, were released from WAS under acidogenic conditions. More importantly, intermediate substrates involved in acidogenic fermentation were advantageous to the cometabolic biodegradation of NP.

Characterization of enzymatic properties of two novel enzymes, 3,4-dihydroxyphenylacetate dioxygenase and 4-hydroxyphenylacetate 3-hydroxylase, from Sulfobacillus acidophilus TPY

Background

As an environmental pollutant, 4-hydroxyphenylacetate (4-HPA) was a product of softwood lignin decomposition and was found in industrial effluents from olive oil production. Sulfobacillus acidophilus TPY was a moderately thermoacidophilic bacterium capable of degrading aromatic compounds including 4-HPA. The enzymes involved in the degradation of 4-HPA and the role of this strain in the bioremediation of marine pollutants need to be illustrated.

Results

3,4-dihydroxyphenylacetate dioxygenase (DHPAO) encoded by mhpB2 and two components of 4-hydroxydroxyphenylacetate (4-HPA) 3-hydroxylase encoded by hpaB and hpaC from S. acidophilus TPY, a moderately thermoacidophilic bacterium, involved in the degradation of 4-HPA possessed quite low amino acid sequence identity (22–53%) with other ever reported corresponding enzymes, which suggest their novelty. These two enzymes were expressed in E. coli and purified to homogeneity. DHPAO activity in E. coli was revealed by spraying with catechol or 3,4-dihydroxyphenylacetate (3,4-DHPA) on the colonies to make them turn brilliant yellow color. DHPAO possessed total activity of 7.81 U and 185.95 U/mg specific activity at the first minute when 3,4-DHPA was served as substrate. DHPAO was a thermophilic enzyme with optimum temperature of 50 °C and optimum substrate of 3,4-DHPA. The small component (HpaC) was a flavoprotein, and both HpaB and HpaC of 4-HPA 3-hydroxylase were NADH-dependent and essential in the conversion of 4-HPA to 3,4-DHPA. 4-HPA 3-hydroxylase possessed 3.59 U total activity and 27.37 U/mg specific activity at the first minute when enzymatic coupled assay with DHPAO was applied in the enzymatic determination.

Conclusions

The ability of this extreme environmental marine strain to degrade catechol and substituted catechols suggest its applications in the bioremediation of catechol and substituted catechols polluted marine environments.

Electronic supplementary material

The online version of this article (10.1186/s12866-019-1415-9) contains supplementary material, which is available to authorized users.

A comprehensive study of conditions of the biodegradation of a plastic additive 2,6-di-tert-butylphenol and proteomic changes in the degraderPseudomonas aeruginosasan ai

ThePseudomonas aeruginosasan ai strain was investigated for its capability to degrade the 2,6-di-tert-butylphenol (2,6-DTBP) plastic additive, a hazardous and toxic substance for aquatic life.

Acidogenic bacteria assisted biodegradation of nonylphenol in waste activated sludge during anaerobic fermentation for short-chain fatty acids production

Nonylphenol (NP) biodegradation under anaerobic conditions is difficult. Here, enhancement of anaerobic NP biodegradation mainly by regulating the role of acidogenic bacteria during anaerobic fermentation of waste activated sludge (WAS) for short-chain fatty acids production is reported. The maximum degradation efficiency of NP (69.4%) was achieved under conditions of pH 10.0 and 10 mg/L Brij 35 within 8 d, which was nearly 3-fold of that in the control (24.6%). Mechanism exploration revealed that the bioavailability of NP and specific NP-degrading bacteria and their functional genes were advantageous to NP biodegradation with alkaline pH and surfactant. More importantly, acidogenic bacteria, the dominant functional bacteria in WAS fermentation systems, were demonstrated to be involved in NP anaerobic biodegradation by providing intermediate organic substrates, as well as through their intrinsic NP-degrading abilities. Possible pathways of NP biodegradation assisted by acidogenic bacteria during anaerobic fermentation were also proposed based on the detected metabolites.

Different pathways for 4-n-nonylphenol biodegradation by two Aspergillus strains derived from estuary sediment: Evidence from metabolites determination and key-gene identification

Nonylphenols (NPs) are known as Endocrine Disputing Chemicals (ECDs) and Persistent Organic Pollutants (POPs) and have attracted continuous attention. Biodegradation is one of the effective ways for pollutant removal in aquatic, sedimentary and soil environments. In this study, two estuarine derived fungi strains, NPF2 and NPF3, were screened from Moshui river estuarine sediment and identified as genus Aspergillus. The growth curves of the two strains as well as the removal and degradation rates for 4-n-NP in Potato Dextrose(PD)medium were used to evaluate their degradation ability. Both strains showed high efficiency for 4-n-NP degradation with 86.03% and 98.76% removal rates in 3 days for NPF2 and NPF3, respectively. Determination of degradation intermediates by LC-MS suggested that the mechanisms for 4-n-NP biodegradation by NPF2 and NPF3 are quite different. Some key functional genes for the two strains also provided supplementary evidences for the different biodegradation mechanism. On strain NPF2, with participation of Cox1, 2 and 3, 4-n-NP degradation starts from reaction at the terminal of the long alkyl chain. The chain reduces one carbon atom once within a cycle of hydroxylation, subsequent oxidation at α-C position and decarboxylation. However, on NPF3, with involvement of sMO, Cel7A, Cel7B and ATEG-00639, 4-n-NP degradation starts from benzene ring, converting into fatty acids. The latter bio-pathway was the first time reported for NPs degradation on fungi.

Diversity shift in bacterial phenol hydroxylases driven by alkyl-phenols in oil refinery wastewaters

Phenol hydroxylases (PHs) play a primary role in the bacterial degradation of phenol and alkylphenols. They are divided into two main classes, single-component and multi-component PHs, having distinctive catalytic subunits designated as PheA1 and LmPH, respectively. The diversity of these enzymes is still largely unexplored. Here, both LmPH and pheA1 gene sequences were examined in activated sludge from oil refinery wastewaters. Phenol, p-cresol, or 3,4-dimethylphenol (3,4-DMP) supplied as extra carbon sources were rapidly mineralized by the microbial community. Analysis of LmPH genes revealed a wide range of sequences, most of which exhibited moderate similarity with homologs found in Proteobacteria. Moreover, the LmPH diversity profiles showed a dramatic shift upon sludge treatment with p-cresol or 3,4-DMP amendment. This resulted in an enrichment in sequences similar to LmPHs from Betaproteobacteria and Gammaproteobacteria. RT-PCR analysis of RNA extracted from wastewater sludge highlighted LmPH genes best expressed in situ. A PCR approach was implemented to analyze the pheA1 gene diversity in the same microbial community. Retrieved sequences fell into four clusters and appeared to be distantly related to pheA1 genes from Actinobacteria. Altogether, our results provide evidence that phenol degraders carrying LmPH are more diverse than PheA1 carrying bacteria and suggest that PHs with best adapted substrate specificity are recruited in response to (methyl)phenol availability.

Biodegradation of the endocrine disrupter 4-tert-octylphenol by the yeast strain Candida rugopelliculosa RRKY5 via phenolic ring hydroxylation and alkyl chain oxidation pathways

4-(1,1,3,3-tetramethylbutane)-phenol (4-tert-OP) is one of the most prevalent endocrine disrupting pollutants. Information about bioremediation of 4-tert-OP remains limited, and no study has been reported on the mechanism of 4-tert-OP degradation by yeasts. The yeast Candida rugopelliculosa RRKY5 was proved to be able to utilize 4-methylphenol, bisphenol A, 4-ethylphenol, 4-tert-butylphenol, 4-tert-OP, 4-tert-nonylphenol, isooctane, and phenol under aerobic conditions. The optimum conditions for 4-tert-OP degradation were 30°C, pH 5.0, and an initial 4-tert-OP concentration of 30mgL^-1; the maximum biodegradation rate constant was 0.107d^-1, equivalent to a minimum half-life of 9.6d. Scanning electron microscopy revealed formation of arthroconidia when cells were grown in the presence of 4-tert-OP, whereas the cells remained in the budding form without 4-tert-OP. Identification of the 4-tert-OP degradation metabolites using liquid chromatography-hybrid mass spectrometry revealed three different mechanisms via both branched alkyl side chain and aromatic ring cleavage pathways.

Nonylphenol biodegradation characterizations and bacterial composition analysis of an effective consortium NP-M2

Nonylphenol (NP), ubiquitously detected as the degradation product of nonionic surfactants nonylphenol polyethoxylates, has been reported as an endocrine disrupter. However, most pure microorganisms can degrade only limited species of NP with low degradation efficiencies. To establish a microbial consortium that can effectively degrade different forms of NP, in this study, we isolated a facultative microbial consortium NP-M2 and characterized the biodegradation of NP by it. NP-M2 could degrade 75.61% and 89.75% of 1000 mg/L NP within 48 h and 8 days, respectively; an efficiency higher than that of any other consortium or pure microorganism reported so far. The addition of yeast extract promoted the biodegradation more significantly than that of glucose. Moreover, surface-active compounds secreted into the extracellular environment were hypothesized to promote high-efficiency metabolism of NP. The detoxification of NP by this consortium was determined. The degradation pathway was hypothesized to be initiated by oxidization of the benzene ring, followed by step-wise side-chain biodegradation. The bacterial composition of NP-M2 was determined using 16S rDNA library, and the consortium was found to mainly comprise members of the Sphingomonas, Pseudomonas, Alicycliphilus, and Acidovorax genera, with the former two accounting for 86.86% of the consortium. The high degradation efficiency of NP-M2 indicated that it could be a promising candidate for NP bioremediation in situ.

Transposon Mutagenesis Identifies Genes Critical for Growth of Pseudomonas nitroreducens TX1 on Octylphenol Polyethoxylates

Pseudomonas nitroreducens TX1 is of special interest because of its ability to utilize 0.05% to 20% octylphenol polyethoxylates (OPEO_n) as a sole source of carbon. In this study, a library containing 30,000 Tn5-insertion mutants of the wild-type strain TX1 was constructed and screened for OPEO_n utilization, and 93 mutants were found to be unable to grow on OPEO_n In total, 42 separate disrupted genes were identified, and the proteins encoded by the genes were then classified into various categories, namely, information storage and processing (14.3%), cellular processes and signaling (28.6%), metabolism (35.7%), and unknown proteins (21.4%). The individual deletion of genes encoding isocitrate lyase (aceA), malate synthase (aceB), and glycolate dehydrogenase (glcE) was carried out, and the requirement for aceA and aceB but not glcE confirmed the role of the glyoxylate cycle in OPEO_n degradation. Furthermore, acetaldehyde dehydrogenase and acetyl-coenzyme A (acetyl-CoA) synthetase activity levels were 13.2- and 2.1-fold higher in TX1 cells grown on OPEO_n than in TX1 cells grown on succinate, respectively. Growth of the various mutants on different carbon sources was tested, and based on these findings, a mechanism involving exoscission to liberate acetaldehyde from the end of the OPEO_n chain during degradation is proposed for the breakdown of OPEO_n IMPORTANCE: Octylphenol polyethoxylates belong to the alkylphenol polyethoxylate (APEO_n) nonionic surfactant family. Evidence based on the analysis of intermediate metabolites suggested that the primary biodegradation of APEO_n can be achieved by two possible pathways for the stepwise removal of the C₂ ethoxylate units from the end of the chain. However, direct evidence for these hypotheses is still lacking. In this study, we described the use of transposon mutagenesis to identify genes critical to the catabolism of OPEO_n by P. nitroreducens TX1. The exoscission of the ethoxylate chain leading to the liberation of acetaldehyde is proposed. Isocitrate lyase and malate synthase in glyoxylate cycle are required in the catabolism of ethoxylated surfactants. Our findings also provide many gene candidates that may help elucidate the mechanisms in stress responses to ethoxylated surfactants by bacteria.

Effects of nonylphenol on key hormonal balances and histopathology of the endangered Caspian brown trout (Salmo trutta caspius)

Endocrine disruptor chemicals (EDCs) potentially pose a hazard to endangered species. Evaluation of the sensitivity of these species to EDCs could be helpful for protecting their populations. So, the present study investigated the adverse effects of nonylphenol, an EDC, on the endocrine hormones and histopathology of male and female juvenile Caspian brown trout (Salmo trutta caspius) following 21 days of exposure to nominal concentrations of 1, 10 and 100 μg/l. The results showed that the HSI and plasma total calcium of male and female fishes exposed to 100 μg/l nonylphenol were significantly increased compared with the control groups (P<0.001). The male plasma T3 level was significantly decreased in 10 (P<0.01) and 100 (P<0.001) μg/l nonylphenol. The female T3 level increased in 1 μg/l nonylphenol concentration (P<0.05). The plasma T4 of males showed significant elevation in fishes exposed to 100 μg/l nonylphenol (P<0.05), but no change for females in any of treatment groups relative to controls (P>0.05). No significant effect of nonylphenol exposure was observed on male plasma TSH levels (P>0.05), whereas, in females, nonylphenol at all concentrations significantly reduced TSH levels. A bell-shaped response was observed in male and female plasma GH levels. Moreover, various histopathological lesions were observed in gill and intestine tissues of fishes exposed to different nonylphenol concentrations. These results demonstrate the high sensitivity of this endangered species to even environmentally relevant concentrations of nonylphenol. Furthermore, Caspian brown trout could be used as bioindicators reflecting the toxicity of nonylphenol.

Aerobic degradation of estrogenic alkylphenols by yeasts isolated from a sewage treatment plant

Long-chain alkylphenols including octylphenol (OP) are well-known toxic pollutants prevailing in the environment due to the massive demand of these chemicals in industry and have been identified as endocrine disrupting chemicals (EDCs).

Insight into the Modulation of Dissolved Organic Matter on Microbial Remediation of PAH-Contaminated Soils

Microorganisms play a key role in degradation of polycyclic aromatic hydrocarbons (PAHs) in environments. Dissolved organic matter (DOM) can enhance microbial degradation of PAHs in soils. However, it is not clear how will the soil microbial community respond to addition of DOM during bioremediation of PAH-contaminated soils. In this study, DOMs derived from various agricultural wastes were applied to remediate the aging PAH-contaminated soils in a 90-day microcosm experiment. Results showed that the addition of DOMs offered a more efficient and persistent elimination of soil PAHs compared to the control which had no DOM addition. PAH removal effects were different among treatments with various DOMs; the addition of DOMs with high proportion of hydrophobic fraction could remove PAHs more efficiently from the soil. Low-molecular-weight (LMW) PAHs were more easily eliminated than that with high-molecular-weight (HMW). Addition of DOMs significantly increased abundance of 16S ribosomal RNA (rRNA), pdo1, nah, and C12O genes and obviously changed community compositions of nah and C12O genes in different ways in the PAH-contaminated soil. Phylogenetic analyses of clone libraries exhibited that all of nah sequences and most of C12O sequences were affiliated into Gammaproteobacteria and Betaproteobacteria. These results suggested that external stimuli produced by DOMs could enhance the microbial degradation of PAHs in soils through not only solubilizing PAHs but also altering abundance and composition of indigenous microbial degraders. Our results reinforce the understanding of role of DOMs in mediating degradation of PAHs by microorganims in soils.

Variation of nonylphenol-degrading gene abundance and bacterial community structure in bioaugmented sediment microcosm

Nonylphenol (NP) can accumulate in river sediment. Bioaugmentation is an attractive option to dissipate heavy NP pollution in river sediment. In this study, two NP degraders were isolated from crude oil-polluted soil and river sediment. Microcosms were constructed to test their ability to degrade NP in river sediment. The shift in the proportion of NP-degrading genes and bacterial community structure in sediment microcosms were characterized using quantitative PCR assay and terminal restriction fragment length polymorphism analysis, respectively. Phylogenetic analysis indicated that the soil isolate belonged to genus Stenotrophomonas, while the sediment isolate was a Sphingobium species. Both of them could almost completely clean up a high level of NP in river sediment (150 mg/kg NP) in 10 or 14 days after inoculation. An increase in the proportion of alkB and sMO genes was observed in sediment microcosms inoculated with Stenotrophomonas strain Y1 and Sphingobium strain Y2, respectively. Moreover, bioaugmentation using Sphingobium strain Y2 could have a strong impact on sediment bacterial community structure, while inoculation of Stenotrophomonas strain Y1 illustrated a weak impact. This study can provide some new insights towards NP biodegradation and bioremediation.

Response of bacterial pdo1, nah, and C12O genes to aged soil PAH pollution in a coke factory area

Soil pollution caused by polycyclic aromatic hydrocarbons (PAHs) is threatening human health and environmental safety. Investigating the relative prevalence of different PAH-degrading genes in PAH-polluted soils and searching for potential bioindicators reflecting the impact of PAH pollution on microbial communities are useful for microbial monitoring, risk evaluation, and potential bioremediation of soils polluted by PAHs. In this study, three functional genes, pdo1, nah, and C12O, which might be involved in the degradation of PAHs from a coke factory, were investigated by real-time quantitative PCR (qPCR) and clone library approaches. The results showed that the pdo1 and C12O genes were more abundant than the nah gene in the soils. There was a significantly positive relationship between the nah or pdo1 gene abundances and PAH content, while there was no correlation between C12O gene abundance and PAH content. Analyses of clone libraries showed that all the pdo1 sequences were grouped into Mycobacterium, while all the nah sequences were classified into three groups: Pseudomonas, Comamonas, and Polaromonas. These results indicated that the abundances of nah and pdo1 genes were positively influenced by levels of PAHs in soil and could be potential microbial indicators reflecting the impact of soil PAH pollution and that Mycobacteria were one of the most prevalent PAHs degraders in these PAH-polluted soils. Principal component analysis (PCA) and correlation analyses between microbial parameters and environmental factors revealed that total carbon (TC), total nitrogen (TN), and dissolved organic carbon (DOC) had positive effects on the abundances of all PAH-degrading genes. It suggests that increasing TC, TN, and DOC inputs could be a useful way to remediate PAH-polluted soils.

Biodegradation of low-ethoxylated nonylphenols in a bioreactor packed with a new ceramic support (Vukopor ® S10)

This work was aimed at studying the possibility of biodegrading 4-nonylphenol and low ethoxylated nonylphenol mixtures, which are particularly recalcitrant to microbial degradation, by employing a biofilm reactor packed with a ceramic support (Vukopor® S10). A selected microbial consortium (Consortium A) was used to colonize the support. 4-Nonylphenol and ethoxylated nonylphenol degradation and mineralization capabilities were studied both in batch and continuous mode. The results showed that Vukopor® S10 was able to be colonized by an active biofilm for the degradation of the target pollutants with the reactor operating both in batch and continuous mode. On the other hand, pollutant adsorption on the support was negligible. FISH showed equal proportion of Alphaproteobacteria and Gammaproteobacteria in the Igepal CO-520 degrading reactor. A shift towards high proportion of Gammaproteobacteria was observed by supplying Igepal CO-210. PCR-density gradient gel electrophoresis (DGGE) analyses also evidenced that the biofilm evolved with time by changing the mixture applied and that Proteobacteria were the most represented phylum in the biofilm. Taken together, the data obtained provide a strong indication that the biofilm reactor packed with Vukopor® S10 and inoculated with Consortium A could potentially be used to develop a technology for the decontamination of 4-nonylphenol and low ethoxylated nonylphenol polluted effluents.

Multiple approaches to characterize the microbial community in a thermophilic anaerobic digester running on swine manure: a case study

In this study, the first survey of microbial community in thermophilic anaerobic digester using swine manure as sole feedstock was performed by multiple approaches including denaturing gradient gel electrophoresis (DGGE), clone library and pyrosequencing techniques. The integrated analysis of 21 DGGE bands, 126 clones and 8506 pyrosequencing read sequences revealed that Clostridia from the phylum Firmicutes account for the most dominant Bacteria. In addition, our analysis also identified additional taxa that were missed by the previous researches, including members of the bacterial phyla Synergistetes, Planctomycetes, Armatimonadetes, Chloroflexi and Nitrospira which might also play a role in thermophilic anaerobic digester. Most archaeal 16S rRNA sequences could be assigned to the order Methanobacteriales instead of Methanomicrobiales comparing to previous studies. In addition, this study reported that the member of Methanothermobacter genus was firstly found in thermophilic anaerobic digester.

Draft Genome Sequence of Pseudomonas nitroreducens Strain TX1, Which Degrades Nonionic Surfactants and Estrogen-Like Alkylphenols

Pseudomonas nitroreducens TX1 ATCC PTA-6168 was isolated from rice field drainage in Taiwan. The bacterium is of special interest because of its capability to use nonionic surfactants (alkylphenol polyethoxylates) and estrogen-like compounds (4-t-octylphenol and 4-nonylphenol) as a sole carbon source. This is the first report on the genome sequence of P. nitroreducens.

Biodegradation of polyethoxylated nonylphenols

Polyethoxylated nonylphenols, with different ethoxylation degrees (NPEO x ), are incorporated into many commercial and industrial products such as detergents, domestic disinfectants, emulsifiers, cosmetics, and pesticides. However, the toxic effects exerted by their degradation products, which are persistent in natural environments, have been demonstrated in several animal and invertebrate aquatic species. Therefore, it seems appropriate to look for indigenous bacteria capable of degrading native NPEO x and its derivatives. In this paper, the isolation of five bacterial strains, capable of using NPEO 15 , as unique carbon source, is described. The most efficient NPEO 15 degrader bacterial strains were identified as Pseudomonas fluorescens (strain Yas2) and Klebsiella pneumoniae (strain Yas1). Maximal growth rates were reached at pH 8, 27°C in a 5% NPEO 15 medium. The NPEO 15 degradation extension, followed by viscometry assays, reached 65% after 54.5 h and 134 h incubation times, while the COD values decreased by 95% and 85% after 24 h for the Yas1 and Yas2 systems, respectively. The BOD was reduced by 99% and 99.9% levels in 24 h and 48 h incubations. The viscosity data indicated that the NPEO 15 biodegradation by Yas2 follows first-order kinetics. Kinetic rate constant (k) and half life time (τ) for this biotransformation were estimated to be 0.0072 h(-1) and 96.3 h, respectively.

Catabolism of 4-alkylphenols by Acinetobacter sp. OP5: genetic organization of the oph gene cluster and characterization of alkylcatechol 2, 3-dioxygenase

In this study, a specific PCR primer set was successfully designed for alkylcatechol 2, 3-dioxygenase genes and applied to detect the presence of this biomarker in 4-t-octylphenol-degrading Acinetobacter sp. strain OP5. A gene cluster (ophRBA1A2A3A4A5A6CEH) encoding multicomponent phenol hydroxylase and alkylcatechol 2, 3-dioxygenase was then cloned from this strain and showed the highest homology to those involved in the published medium-chain alkylphenol gene clusters. The pure enzyme of recombinant cell harboring ophB showed meta-cleavage activities for 4-methylcatechol (1,435%), 4-ethylcatechol (982%), catechol (100%), 4-t-butylcatechol (16.6%), and 4-t-octylcatechol (3.2%). The results suggest that the developed molecular technique is useful and easy in detection of medium/long-chain alkylphenol degradation gene cluster. In addition, it also provides a better understanding of the distribution of biodegradative genes and pathway for estrogenic-active long-chain alkylphenols in bacteria.

Biodegradation of nonylphenols using nitrifying sludge, 4-chlorophenol-adapted consortia and activated sludge in liquid and solid phases

The biodegradation of a technical mixture of nonylphenols (tNP) with three different biomasses (nitrifying sludge, 4-chlorophenol-adapted consortia and activated sludge) was evaluated in batch tests. The tNP degradation was determined in solid and liquid phases. The three biomasses studied were able to biodegrade the technical mixture of nonylphenols. It was found that 33% to 44% of the initial tNP was adsorbed on to the sludge after 250 h. Nitrifying sludge presented the highest biodegradation percentage (43.1% +/- 2.3%) and degradation rate (3.10 x 10(-3) micromol/d). Acclimated 4-chlorophenol and activated sludge degraded 34.3% +/- 1.2% and 18.2% +/- 0.5% of the initial tNP, respectively. Actual half-life times of 10.9, 12.0 and 22.8 days were obtained for the biodegradation of tNP by nitrifying, acclimated 4-chlorophenol and activated sludge, respectively. It was concluded that, although nitrifiying biomass posses a high initial adsorption rate, this biomass can also biodegrade the tNP faster than the other tested biomasses.

Occurrence and biodegradation of nonylphenol in the environment

Nonylphenol (NP) is an ultimate degradation product of nonylphenol polyethoxylates (NPE) that is primarily used in cleaning and industrial processes. Its widespread use has led to the wide existence of NP in various environmental matrices, such as water, sediment, air and soil. NP can be decreased by biodegradation through the action of microorganisms under aerobic or anaerobic conditions. Half-lives of biodegradation ranged from a few days to almost one hundred days. The degradation rate for NP was influenced by temperature, pH and additions of yeast extracts, surfactants, aluminum sulfate, acetate, pyruvate, lactate, manganese dioxide, ferric chloride, sodium chloride, hydrogen peroxide, heavy metals, and phthalic acid esters. Although NP is present at low concentrations in the environment, as an endocrine disruptor the risks of long-term exposure to low concentrations remain largely unknown. This paper reviews the occurrence of NP in the environment and its aerobic and anaerobic biodegradation in natural environments and sewage treatment plants, which is essential for assessing the potential risk associated with low level exposure to NP and other endocrine disruptors.

Design of PCR Primers for the mcrA Genes Detection of Methanogen Communities

Methanogens play an important role to carbon cycling, catalyzing the production of methane and carbon dioxide, both potent green house gases, during organic matter degradation in anaerobic environments. Therefore, it is necessary to better understand microorganisms that produce natural gas. Indeed, methanogens are difficult to perform through culture based methods. In addition, the culture independent methods using the 16S rRNA gene also revealed some disadvantages. For these reasons, the culture independent molecular techniques using the specific catabolic genes such as methyl coenzyme M reductase (MCR) were studied. In this study, a primer set which can amplify specific fragments from a wide variety of mcrA gene was designed based on the homologous regions of 100 mcrA genes listed in the GenBank. PCR with the mcrA primers amplified DNA fragments of the expected size from all the six samples which obtained from biogas production reactors. In addition, denaturing gradient gel electrophoresis PCR analysis using our designed primers also revealed the diversity of mcrA gene in each sample. These results revealed that our primers were successfully to detect the mcrA genes and it is also helpful to know the diversity of mcrA genes in methanogen communities.