Complete genome sequence of Gordonia sp. YC-JH1, a bacterium efficiently degrading a wide range of phthalic acid esters

Simultaneously degradation of various phthalate esters by Rhodococcus sp. AH-ZY2: Strain, omics and enzymatic study

Phthalate esters (PAEs) are widely used as plasticizers and cause serious complex pollution problem in environment. Thus, strains with efficient ability to simultaneously degrade various PAEs are required. In this study, a newly isolated strain Rhodococcus sp. AH-ZY2 can degrade 500 mg/L Di-n-octyl phthalate completely within 16 h and other 500 mg/L PAEs almost completely within 48 h at 37 °C, 180 rpm, and 2 % (v/v) inoculum size of cultures with a OD600 of 0.8. OD600 = 0.8, 2 % (v/v). Twenty genes in its genome were annotated as potential esterase and four of them (3963, 4547, 5294 and 5359) were heterogeneously expressed and characterized. Esterase 3963 and 4547 is a type I PAEs esterase that hydrolyzes PAEs to phthalate monoesters. Esterase 5294 is a type II PAEs esterase that hydrolyzes phthalate monoesters to phthalate acid (PA). Esterase 5359 is a type III PAEs esterase that simultaneously degrades various PAEs to PA. Molecular docking results of 5359 suggested that the size and indiscriminate binding feature of spacious substrate binding pocket may contribute to its substrate versatility. AH-ZY2 is a potential strain for efficient remediation of PAEs complex pollution in environment. It is first to report an esterase that can efficiently degrade mixed various PAEs.

Exploring di (2-ethylhexyl) phthalate degradation by a synthetic marine bacterial consortium: Genomic insights, pathway and interaction prediction, and application in sediment microcosms

Di (2-ethylhexyl) phthalate (DEHP), a toxic phthalate ester (PAE) plasticizer, is often detected in marine sediment and biota. Our understanding of DEHP-degrading marine bacteria and the associated genetic mechanisms is limited. This study established a synthetic bacterial consortium (A02) consisting of three marine bacteria (OR05, OR16, and OR21). Consortium A02 outperformed the individual strains in DEHP degradation. Investigations into the degradation of DEHP intermediates revealed that OR05 and OR16 likely contributed to enhanced DEHP degradation by Consortium A02 via the utilization of DEHP intermediates, such as protocatechuic acid and mono (ethylhexyl) phthalate, with OR21 as the key DEHP degrader. A pathway of DEHP degradation by Consortium A02 was predicted based on genome analysis and experimental degradation. Bioaugmentation with Consortium A02 led to 80% DEHP degradation in 26 days in saline sediment (100 mg/kg), surpassing the 53% degradation by indigenous microbes, indicating the potential of A02 for treating DEHP-contaminated sediments. Meanwhile, bioaugmentation notably changed the bacterial community, with the exclusive presence of certain bacterial genera in the A02 bioaugmented microcosms, and was predicted to result in a more dynamic and active sediment bacterial community. This study contributes to the limited literature on DEHP degradation by marine bacteria and their associated genes.

Mechanisms and high-value applications of phthalate isomers degradation pathways in bacteria

Phthalate isomers are key intermediates in the biodegradation of pollutants including waste polyethylene terephthalate (PET) plastics and plasticizers. So far, an increasing number of phthalate isomer-degrading strains have been isolated, and their degradation pathways show significant diversity. In this paper, we comprehensively review the current status of research on the degrading bacteria, degradation characteristics, aerobic and anaerobic degradation pathways, and degradation genes (clusters) of phthalate isomers, and discuss the current shortcomings and challenges. Moreover, the degradation process of phthalate isomers produces many important aromatic precursor molecules, which can be used to produce higher-value derivative chemicals, and the modification of their degradation pathways holds good prospects. Therefore, this review also highlights the current progress made in modifying the phthalate isomer degradation pathway and explores its potential for high-value applications.

Low dose phosphorus supplementation is conducive to remediation of heavily petroleum-contaminated soil-From the perspective of hydrocarbon removal and ecotoxicity risk control

Biostimulation by supplementing of nitrogen and phosphorus nutrients is a common strategy for remediation of petroleum-polluted soils. However, the dosage influence of exogenous nitrogen or phosphorus on petroleum hydrocarbon removal and soil ecotoxicity and microbial function remain unclear. In this study, we compared the efficiencies of hydrocarbon degradation and ecotoxicity control by experiment conducted over addition of inorganic nitrogen or phosphorus at C/N ratio of 100/10, C/N/P ratio of 100/10/1, and C/P ratio of 100/1 in a heavily petroleum-contaminated loessal soil with 12,320 mg/kg of total petroleum hydrocarbon (TPH) content. A 90-day incubation study revealed that low-dose of phosphorus addition with the C/P ratio of 100/1 promoted hydrocarbon degradation and reduced soil ecotoxicity. Microbial community composition analysis suggested that phosphorus addition enriched hydrocarbon degrader Gordonia and Mycolicibacterium genus. The key enzymes EC 5.3.3.8, EC 6.2.1.20 and EC 6.4.1.1 which referred to degradation of long-chain hydrocarbons, unsaturated fatty acids and pyruvate metabolism were abundance by phosphorus supplementation. While nitrogen addition at C/N ratio of 100/10 or C/N/P ratio of 100/10/1 inhibited hydrocarbon degradation and exacerbated soil ecotoxicity due to promoting denitrification and coupling reactions with hydrocarbons. Our results suggested that low-dose phosphorus addition served as a favorable strategy to promote crude oil remediation and ecotoxicity risk control in heavily petroleum-contaminated soil. Hence, the application of suitable doses of exogenous biostimulants is an efficient approach to restore the ecological functions of organically contaminated soils.

Comparing the removal efficiency of diisobutyl phthalate by Bacillariophyta, Cyanophyta and Chlorophyta

The utilization of microalgae for both removing phthalate esters (PAEs) from wastewater and producing bioenergy has become a popular research topic. However, there is a lack of studies comparing the effectiveness of different types of microalgae in removing these harmful compounds. Therefore, the present study aimed to evaluate and compare the efficiency of various processes, such as hydrolysis, photolysis, adsorption, and biodegradation, in removing diisobutyl phthalate (DiBP) using six different species of microalgae. The study indicated that the average removal efficiency of DiBP (initial concentrations of 5, 0.5, and 0.05 mg L-1) by all six microalgae (initial cell density of 1 × 106 cells mL-1) was in the order of Scenedesmus obliquus (95.39 %) > Chlorella vulgaris (94.78 %) > Chroococcus sp. (91.16 %) > Cyclotella sp. (89.32 %) > Nitzschia sp. (88.38 %) > Nostoc sp. (84.33 %). The results of both hydrolysis and photolysis experiments revealed that the removal of DiBP had minimal impact, with respective removal efficiencies of only 0.89 % and 1.82 %. The adsorption efficiency of all six microalgae decreased significantly with increasing initial DiBP concentrations, while the biodegradation efficiency was elevated. Chlorella vulgaris and Chroococcus sp. demonstrated the highest adsorption and biodegradation efficiencies among the microalgae tested. Scenedesmus obliquus was chosen for the analysis of the degradation products of DiBP due to its exceptional ability to remove DiBP. The analysis yielded valuable results, identifying monoisobutyl phthalate (MiBP), phthalic acid (PA), and salicylic acid (SA) as the possible degradation products of DiBP. The possible degradation pathways mainly included dealkylation, the addition of hydroxyl groups, and decarboxylation. This study lays a theoretical foundation for the elimination of PAEs in the aquatic environment.

Complete degradation of di-n-butyl phthalate by Glutamicibacter sp. strain 0426 with a novel pathway

Di-n-butyl phthalate (DBP) is widely used as plasticizer that has potential carcinogenic, teratogenic, and endocrine effects. In the present study, an efficient DBP-degrading bacterial strain 0426 was isolated and identified as a Glutamicibacter sp. strain 0426. It can utilize DBP as the sole source of carbon and energy and completely degraded 300 mg/L of DBP within 12 h. The optimal conditions (pH 6.9 and 31.7 °C) for DBP degradation were determined by response surface methodology and DBP degradation well fitted with the first-order kinetics. Bioaugmentation of contaminated soil with strain 0426 enhanced DBP (1 mg/g soil) degradation, indicating the application potential of strain 0426 for environment DBP removal. Strain 0426 harbors a distinctive DBP hydrolysis mechanism with two parallel benzoate metabolic pathways, which may account for the remarkable performance of DBP degradation. Sequences alignment has shown that an alpha/beta fold hydrolase (WP_083586847.1) contained a conserved catalytic triad and pentapeptide motif (GX1SX2G), of which function is similar to phthalic acid ester (PAEs) hydrolases and lipases that can efficiently catalyze hydrolysis of water-insoluble substrates. Furthermore, phthalic acid was converted to benzoate by decarboxylation, which entered into two different pathways: one is the protocatechuic acid pathway under the role of pca cluster, and the other is the catechol pathway. This study demonstrates a novel DBP degradation pathway, which broadens our understanding of the mechanisms of PAE biodegradation.

Micro (nano)plastics and phthalate esters drive endophytic bacteria alteration and inhibit wheat root growth

Endophytes play an important role in plant growth and stress tolerance, but limited information is available on the complex effects of micro (nano)plastics and phthalate esters (PAEs) on endophytes in terrestrial plants. To better elucidate the ecological response of endophytic bacteria on exogenous pollutants, a hydroponic experiment was conducted to examine the combined impact of polystyrene (PS) and PAEs on endophyte community structure, diversity, and wheat growth. The findings revealed that wheat roots were capable of absorbing and accumulating PS nanoparticles (PS-NPs, 0.1 μm), whereas PS microparticles (PS-MPs, 1 and 10 μm) merely adhered to the root surface. The addition of PAEs resulted in a stronger accumulation of fluorescent signal from PS-NPs in the roots. The dibutyl phthalate (DBP) and di(2-ethylhexyl) phthalate (DEHP) were identified in wheat roots, and they could be metabolized to form minobutyl phthalate and phthalic acid, and mono-(2-ethylhexyl) phthalate, respectively. Compared to single PAEs, the concentration of PAEs and their metabolites in the roots treated with PS-NPs showed a great increase, while they exhibited a significant decline in the presence of PS-MPs. Principal coordinate analysis and permutational multivariate analysis of variance demonstrated that PS size were the major factor that induced oxidative damage, and altered the endogenous homeostasis of wheat roots. The increase in PS size positively promoted the relative abundance of dominant endophytes. Specifically, Proteobacteria. Proteobacteria were the most important in the symbiosis survival, which had a great impact on the microbial community and diversity. Therefore, PS and PAEs could affect the endophytes directly and indirectly. Structural equation modeling further implied that these endophytic bacteria, along with antioxidant enzymes such as superoxide dismutase which were regulated by non-enzymatic mechanisms, promoted root biomass increase. These results indicated a synergistic resistance mechanism between antioxidant enzymes and endophytic bacteria in response to environmental stress.

An indigenous tubular ceramic membrane integrated bioreactor system for biodegradation of phthalates mixture from contaminated wastewater

Endocrine-disrupting phthalates (EDPs) are widely used as plasticizers for the manufacture of different plastics and polyvinyl chloride by providing flexibility and mechanical strength. On the other hand, they are categorized under priority pollutants list due to their threat to human health and the environment. This study examined biodegradation of a mixture of dimethyl, diethyl, dibutyl, benzyl butyl, di-2-ethylhexyl, and di-n-octyl phthalates using a CSTB (continuous stirred tank bioreactor) operated under batch, fed-batch, continuous, and continuous with biomass recycle operation modes. For operating the CSTB under biomass recycle mode, microfiltration using an indigenous tubular ceramic membrane was employed. Ecotoxicity assessment of the treated water was carried out to evaluate the toxicity removal efficiency by the integrated bioreactor system. From the batch experiments, the EDPs cumulative degradation values were 90 and 75% at 1250 and 1500 mg/L total initial concentration of the mixture, respectively, whereas complete degradation was achieved at 750 mg/L. In the fed-batch study, 93% degradation was achieved at 1500 mg/L total initial concentration of the mixture. In continuous operation mode, 94 and 85% degradation efficiency values were achieved at 43.72 and 52.08 mg/L⋅h inlet loading rate of phthalate mixture. However, continuous feeding with 100% biomass recycle revealed complete degradation at 41.67 mg/L⋅h inlet loading rate within the 84 h operation period. High seed germination index and low mortality percentage of brine shrimps observed with phthalate degraded water from the integrated bioreactor system revealed its excellent potential in the treatment and toxicity removal of phthalates contaminated environment.

Genome sequence of Gordonia alkaliphila strain WW102, isolated from influent wastewater at a research center with multiple-species research animal facilities

Gordonia alkaliphila is a little known mesophilic Gram-positive rod-shaped bacterium. We report the 3.85-Mbp genome sequence of G. alkaliphila strain WW102, isolated from wastewater at a research center with multiple-species laboratory animal facilities. The genome predicted FadD32 gene clusters that are involved in the biosynthesis of mycolic acids as found in Mycobacterium tuberculosis.

A Novel and Efficient Phthalate Hydrolase from Acinetobacter sp. LUNF3: Molecular Cloning, Characterization and Catalytic Mechanism

Phthalic acid esters (PAEs), which are widespread environmental contaminants, can be efficiently biodegraded, mediated by enzymes such as hydrolases. Despite great advances in the characterization of PAE hydrolases, which are the most important enzymes in the process of PAE degradation, their molecular catalytic mechanism has rarely been systematically investigated. Acinetobacter sp. LUNF3, which was isolated from contaminated soil in this study, demonstrated excellent PAE degradation at 30 °C and pH 5.0-11.0. After sequencing and annotating the complete genome, the gene dphAN1, encoding a novel putative PAE hydrolase, was identified with the conserved motifs catalytic triad (Ser201-Asp295-His325) and oxyanion hole (H127GGG130). DphAN1 can hydrolyze DEP (diethyl phthalate), DBP (dibutyl phthalate) and BBP (benzyl butyl phthalate). The high activity of DphAN1 was observed under a wide range of temperature (10-40 °C) and pH (6.0-9.0). Moreover, the metal ions (Fe2+, Mn2+, Cr2+ and Fe3+) and surfactant TritonX-100 significantly activated DphAN1, indicating a high adaptability and tolerance of DphAN1 to these chemicals. Molecular docking revealed the catalytic triad, oxyanion hole and other residues involved in binding DBP. The mutation of these residues reduced the activity of DphAN1, confirming their interaction with DBP. These results shed light on the catalytic mechanism of DphAN1 and may contribute to protein structural modification to improve catalytic efficiency in environment remediation.

Analysis of the performance of the efficient di-(2-ethylhexyl) phthalate-degrading bacterium Rhodococcus pyridinovorans DNHP-S2 and associated catabolic pathways

The widespread use of plastic has led to the global occurrence of phthalate esters (PAEs) pollution. PAEs can be effectively removed from polluted environments by microbe-mediated degradation. Di-(2-ethylhexyl) phthalate (DEHP) has the highest residual concentration in agricultural soil-contaminated areas compared to other PAEs in most of China. The Rhodococcus pyridinovorans DNHP-S2 microbial isolate identified was found to efficiently degrade DEHP. Within a 72 h period, the bacteria were able to degrade 52.47% and 99.75% of 500 mg L^-1 DEHP at 10 °C and 35 °C, respectively. Dimethyl phthalate (DMP) was first identified as an intermediate metabolite of DEHP, which is different from the previously reported DEHP catabolic pathway. Genomic sequencing of DNHP-S2 identified benzoate 1,2-dioxygenase and catechol 2,3/1,2-dioxygenase as potential mediators of DEHP degradation, consistent with the existence of two downstream metabolic pathways governing DEHP degradation. Three targets DEHP metabolism-related enzymes were found to be DEHP-inducible at the mRNA level, and DNHP-S2 was able to mediate the complete degradation of DEHP at lower temperatures, as confirmed via RT-qPCR. DNHP-S2 was also found to readily break down other PAEs including DMP, di-n-butyl phthalate (DBP), di-n-octyl phthalate (DnOP), and n-butyl benzyl phthalate (BBP). Together, these results thus highlight DNHP-S2 as a bacterial strain with great promise as a tool for the remediation of PAE pollution. In addition to providing new germplasm and genetic resources for use in the context of PAE degradation, these results also offer new insight into the potential mechanisms whereby PAEs undergo catabolic degradation, making them well-suited for use in PAE-contaminated environments.

Biodegradation of Dibutyl Phthalate by the New Strain Acinetobacter baumannii DP-2

Optimizing the culture conditions of DBP degradation by bacteria and investigating its biodegradation pathways have a great importance to develop effective PAEs pollution control strategies. In this study, we investigated the cultivation condition optimization, degradation kinetics, and degradation pathways of a newly isolated dibutyl phthalate (DBP) degradation strain, which was isolated from activated sludge and identified as Acinetobacter baumannii DP-2 via morphological observation, biochemical identification, and 16S rDNA sequence analysis. The degradation conditions were optimized based on the results of single-factor experiments and response surface optimization experiments. The DBP degradation rate of Acinetobacter baumannii DP-2 reached up to 85.86% when the inoculation amount was 17.14%, the DBP concentration was 9.81 mg·L^-1 and the NaCl concentration was 5 g·L^-1. The GC-MS analysis results indicated that the intermediate metabolites of Acinetobacter baumannii DP-2 mainly consisted of DMP, MBP, PA, and benzoic acid derivatives, which confirmed the degradation pathway from DBP to PA under aerobic pathway and then to BA under anaerobic pathway. In summary, Acinetobacter baumannii DP-2 shows great potential for the degradation of DBP in contaminated soils.

Omics and mechanistic insights into di-(2-ethylhexyl) phthalate degradation in the O2-fluctuating estuarine sediments

Di-(2-ethylhexyl) phthalate (DEHP) represents the most used phthalate plasticizer with an annual production above the millions of tons worldwide. Due to its inadequate disposal, outstanding chemical stability, and extremely low solubility (3 mg/L), endocrine-disrupting DEHP often accumulates in urban estuarine sediments at concentrations above the predicted no-effect concentration (20-100 mg/kg). Our previous study suggested that microbial DEHP degradation in estuarine sediments proceeds synergistically where DEHP side-chain hydrolysis to form phthalic acid represents a bottleneck. Here, we resolved this bottleneck and deconstructed the microbial synergy in O₂-fluctuating estuarine sediments. Metagenomic analysis and RNA sequencing suggested that orthologous genes encoding extracellular DEHP hydrolase NCU65476 in Acidovorax sp. strain 210-6 are often flanked by the co-expressed composite transposon and are widespread in aquatic environments worldwide. Therefore, we developed a turbidity-based microplate assay to characterize NCU65476. The optimized assay conditions (with 1 mM Ca²⁺ and pH 6.0) increased the DEHP hydrolysis rate by a factor of 10. Next, we isolated phthalic acid-degrading Hydrogenophaga spp. and Thauera chlorobenzoica from Guandu estuarine sediment to study the effect of O_2(aq) on their metabolic synergy with strain 210-6. The results of co-culture experiments suggested that after DEHP side-chain hydrolysis by strain 210-6, phthalic acid can be degraded by Hydrogenophaga sp. when O_2(aq) is above 1 mg/L or degraded by Thauera chlorobenzoica anaerobically. Altogether, our data demonstrates that DEHP could be degraded synergistically in estuarine sediments via divergent pathways responding to O₂ availability. The optimized conditions for NCU65476 could facilitate the practice of DEHP bioremediation in estuarine sediments.

Phthalate Esters Metabolic Strain Gordonia sp. GZ-YC7, a Potential Soil Degrader for High Concentration Di-(2-ethylhexyl) Phthalate

As commonly used chemical plasticizers in plastic products, phthalate esters have become a serious ubiquitous environmental pollutant, such as in soil of plastic film mulch culture. Microbial degradation or transformation was regarded as a suitable strategy to solve the phthalate esters pollution. Thus, a new phthalate esters degrading strain Gordonia sp. GZ-YC7 was isolated in this study, which exhibited the highest di-(2-ethylhexyl) phthalate degradation efficiency under 1000 mg/L and the strongest tolerance to 4000 mg/L. The comparative genomic analysis results showed that there exist diverse esterases for various phthalate esters such as di-(2-ethylhexyl) phthalate and dibutyl phthalate in Gordonia sp. GZ-YC7. This genome characteristic possibly contributes to its broad substrate spectrum, high degrading efficiency, and high tolerance to phthalate esters. Gordonia sp. GZ-YC7 has potential for the bioremediation of phthalate esters in polluted soil environments.

Diversity of endophytic bacteria in wild rice (Oryza meridionalis) and potential for promoting plant growth and degrading phthalates

Phthalates (PAEs) accumulated in agricultural soils and rice have increased human exposure risks. Microbial degradation could efficiently reduce the residue of organic pollutants in soil and crop plants. Here, we hypothesized that endophytic bacteria from wild rice have the potential for degradation of PAEs and plant growth promoting. The endophytic bacterial community and functional diversity in wild rice (Oryza meridionalis) were analyzed for the first time, and the potential for PAE degradation and plant growth promoting by endophytes were investigated. The results of Illumina high-throughput sequencing revealed that abundant endophytes inhabited in wild rice with Proteobacteria, Bacteroidetes, Firmicutes and Actinobacteria being the dominant phyla. Endophytic bacterial diversity and complexity were confirmed by isolation and clustering of isolates. Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis demonstrated that endophytes exerted diverse functions such as plant growth promoting, xenobiotics biodegradation, pollution remediation and bacterial chemotaxis. Pure culture experiment showed that 30 isolated endophytic strains exhibited in vitro plant growth promoting activities, and rice plants inoculated with these strains confirmed their growth promoting abilities. Some endophytic strains were capable of efficiently degrading PAEs, with the highest removal percentage of di-n-butyl phthalate (DBP) up to 96.1% by Bacillus amyloliquefaciens strain L381 within 5 days. Synthetic community F and strain L381 rapidly removed DBP from soil (removing 91.0%-99.2% within 10 d and from rice plant slurry (removing 93.4%-99.2% within 5 d). These results confirmed the hypothesis and demonstrated the diversity of endophytic bacteria in wild rice with diverse functions, especially for plant growth promoting and removing PAEs. These multifunctional endophytic bacteria provided good alternatives to reduce PAE accumulation in crops and increase yield.

Stress proteins, nonribosomal peptide synthetases, and polyketide synthases regulate carbon sources-mediated bio-demulsifying mechanisms of nitrate-reducing bacterium Gordonia sp. TD-4

Carbon sources have been reported to determine the bio-demulsifying performance and mechanisms. However, the genetic regulation of carbon sources-mediated bio-demulsification remains unclear. Here, the effects of β-oxidation, stress response, and nitrate metabolism on the demulsification of alkaline-surfactant-polymer flooding produced water by Gordonia sp. TD-4 were investigated. The results showed that competitive adsorption-derived demulsification was mediated by oil-soluble carbon sources (paraffin). Surface-active lipopeptides responsible for competitive adsorption-derived demulsification could be biosynthesized by the nonribosomal peptide synthetases and polyketide synthases using oil-soluble carbon sources. Bio-flocculation-derived demulsification was mediated by water-soluble carbon sources. Water-soluble carbon sources (sodium acetate and glucose) mediated the process of the dissimilatory reduction of nitrate to ammonia, which resulted in the variable accumulation of nitrite. The accumulated nitrite (>180 mg-N/L) stimulated stress response and induced the upregulation of chaperone-associated genes. The upregulation of chaperonins increased the cell surface hydrophobicity and the cation-dependent bio-flocculating performance, which were responsible for bio-flocculation-derived demulsification. The β-oxidation of fatty acids significantly affected both competitive adsorption-derived demulsification and bio-flocculation-derived demulsification. This study illustrates the synergistic effects of nitrogen sources and carbon sources on the regulation of bio-demulsifying mechanisms of TD-4 and identifies two key functional gene modules responsible for the regulation of bio-demulsifying mechanisms.

Colorimetric assay based on arginine-functionalized gold nanoparticles for the detection of dibutyl phthalate in Baijiu samples

In this paper, a simple and innovative colorimetric method is established, which is based on DBP-induced aggregation of arginine functionalized gold nanoparticles (ARG-AuNPs), and can be used for the sensitive determination of dibutyl phthalate (DBP) in Baijiu samples. The morphological characteristics and the color changes of ARG-AuNPs caused by aggregation show good sensitivity, and can be observed through ultraviolet-visible spectroscopy, Fourier transform infrared (FT-IR) spectroscopy, transmission electron microscopy (TEM), dynamic light scattering (DLS) and zeta potential technology. The color change of ARG-AuNPs from red to blue is due to the strong non-covalent interactions between DBP and ARG-AuNPs (electrostatic, van der Waals force and hydrogen bonding), which leads to the reduction of the electrostatic repulsion between the nanoparticles and aggregation. A two-stage linear equation was established between the absorption ratio (A₆₉₀/A₅₃₀) and the DBP concentration (0.0-2.8 mg L^-1); the correlation coefficient (R²) was 0.9914-0.9940, and the detection limit (LOD) was estimated at 0.05 mg L^-1. The designed ARG-AuNPs acting as a dependable sensor for the detection of Baijiu samples equally acquired satisfactory recoveries. When the concentration of DBP in the solution is more than 1.0 mg L^-1, the color change can be clearly observed by the naked eye; so there is no need for sample preparation techniques and tedious operations to quickly and semi-quantitatively detect DBP. The successful application of the proposed method in Baijiu samples indicates its potential to detect DBP in more complex environment samples.

Role of mitochondria-endoplasmic reticulum coupling in lycopene preventing DEHP-induced hepatotoxicity

Di (2-ethylhexyl) phthalate (DEHP) is a hazardous compound used as a plasticizer in plastic products. As a natural carotenoid, lycopene (LYC) is considered an effective protective agent against various types of organ damage. The present study aimed to investigate the role of mitochondria-endoplasmic reticulum (ER) coupling in LYC preventing DEHP-induced hepatotoxicity. The mice were treated with LYC (5 mg kg^-1) and/or DEHP (500 or 1000 mg kg^-1). In the present study, LYC prevented DEHP-induced histopathological changes including fibrosis and glycogen storage in the liver. Additionally, LYC alleviated DEHP-induced ultrastructural injury of mitochondria and ER. LYC had the underlying preventability against DEHP-induced mitochondrial dynamics imbalance including an increase in fission and a decrease in fusion. Furthermore, DEHP induced mitochondria-associated endoplasmic reticulum membrane (MAM) disorder-induced ER stress through the ER unfolded protein response (UPR^ER), but LYC alleviated these alterations. Therefore, LYC prevented DEHP-induced hepatic mitochondrial dynamics and MAM disorder, leading to ER stress. The present study provides novel evidence of mitochondria-ER coupling as a target for LYC that prevents DEHP-induced hepatotoxicity.

Bacteria-driven phthalic acid ester biodegradation: Current status and emerging opportunities

The extensive use of phthalic acid esters (PAEs) has led to their widespread distribution across various environments. As PAEs pose significant threats to human health, it is urgent to develop efficient strategies to eliminate them from environments. Bacteria-driven PAE biodegradation has been considered as an inexpensive yet effective strategy to restore the contaminated environments. Despite great advances in bacterial culturing and sequencing, the inherent complexity of indigenous microbial community hinders us to mechanistically understand in situ PAE biodegradation and efficiently harness the degrading power of bacteria. The synthetic microbial ecology provides us a simple and controllable model system to address this problem. In this review, we focus on the current progress of PAE biodegradation mediated by bacterial isolates and indigenous bacterial communities, and discuss the prospective of synthetic PAE-degrading bacterial communities in PAE biodegradation research. It is anticipated that the theories and approaches of synthetic microbial ecology will revolutionize the study of bacteria-driven PAE biodegradation and provide novel insights for developing effective bioremediation solutions.

Integrated Multi-omics Investigations Reveal the Key Role of Synergistic Microbial Networks in Removing Plasticizer Di-(2-Ethylhexyl) Phthalate from Estuarine Sediments

Di-(2-ethylhexyl) phthalate (DEHP) is the most widely used plasticizer worldwide, with an annual global production of more than 8 million tons. Because of its improper disposal, endocrine-disrupting DEHP often accumulates in estuarine sediments in industrialized countries at submillimolar levels, resulting in adverse effects on both ecosystems and human beings. The microbial degraders and biodegradation pathways of DEHP in O₂-limited estuarine sediments remain elusive. Here, we employed an integrated meta-omics approach to identify the DEHP degradation pathway and major degraders in this ecosystem. Estuarine sediments were treated with DEHP or its derived metabolites, o-phthalic acid and benzoic acid. The rate of DEHP degradation in denitrifying mesocosms was two times slower than that of o-phthalic acid, suggesting that side chain hydrolysis of DEHP is the rate-limiting step of anaerobic DEHP degradation. On the basis of microbial community structures, functional gene expression, and metabolite profile analysis, we proposed that DEHP biodegradation in estuarine sediments is mainly achieved through synergistic networks between denitrifying proteobacteria. Acidovorax and Sedimenticola are the major degraders of DEHP side chains; the resulting o-phthalic acid is mainly degraded by Aestuariibacter through the UbiD-dependent benzoyl coenzyme A (benzoyl-CoA) pathway. We isolated and characterized Acidovorax sp. strain 210-6 and its extracellular hydrolase, which hydrolyzes both alkyl side chains of DEHP. Interestingly, genes encoding DEHP/mono-(2-ethylhexyl) phthalate (MEHP) hydrolase and phthaloyl-CoA decarboxylase—key enzymes for side chain hydrolysis and o-phthalic acid degradation, respectively—are flanked by transposases in these proteobacterial genomes, indicating that DEHP degradation capacity is likely transferred horizontally in microbial communities.

IMPORTANCE Xenobiotic phthalate esters (PAEs) have been produced on a considerably large scale for only 70 years. The occurrence of endocrine-disrupting di-(2-ethylhexyl) phthalate (DEHP) in environments has raised public concern, and estuarine sediments are major DEHP reservoirs. Our multi-omics analyses indicated that complete DEHP degradation in O₂-limited estuarine sediments depends on synergistic microbial networks between diverse denitrifying proteobacteria and uncultured candidates. Our data also suggested that the side chain hydrolysis of DEHP, rather than o-phthalic acid activation, is the rate-limiting step in DEHP biodegradation within O₂-limited estuarine sediments. Therefore, deciphering the bacterial ecophysiology and related biochemical mechanisms can help facilitate the practice of bioremediation in O₂-limited environments. Furthermore, the DEHP hydrolase genes of active DEHP degraders can be used as molecular markers to monitor environmental DEHP degradation. Finally, future studies on the directed evolution of identified DEHP/mono-(2-ethylhexyl) phthalate (MEHP) hydrolase would bring a more catalytically efficient DEHP/MEHP hydrolase into practice.

Biodegradation of Di (2-Ethylhexyl) Phthalate by a novel Enterobacter spp. Strain YC-IL1 Isolated from Polluted Soil, Mila, Algeria

Di-(2-ethylhexyl) phthalate (DEHP) is one of the phthalic acid ester representatives and is mainly used as a plasticizer to endow polyvinyl chloride plastics with desirable physical properties. It is synthesized in massive amounts worldwide. Many studies have proved the adverse effects of DEHP on human health and wildlife. DEHP is labeled as an endocrine disruptor which causes human reproductive problems. Enterobacter spp. YC-IL1, a novel isolated strain from contaminated soil, was identified by 16S rRNA gene analysis and electronic microscope. It is capable of efficiently degrading DEHP (100%) and a wide range of phthalic acid ester PAEs, particularly those containing side chains with branches, or ring structures such as dutylbenzyl phthalate and dicyclohexyl phthalate, which are hard to degrade, with, respectively, 81.15% and 50.69% degradation after 7 days incubation. YC-IL1 is an acido-tolerant strain which remained in pH values lower than pH 5.0 with the optimum pH 7.0 and temperature 30 °C. The DEHP metabolites were detected using HPLC-QQQ and then the degradation pathway was tentatively proposed. Strain YC-IL1 showed high DEHP degradation rate in artificially contaminated soil with 86% removed in 6 days. These results indicate the application potential of YC-IL1 in bioremediation of PAE-polluted sites, even the acidic ones.

Bioremediation of di-(2-ethylhexyl) phthalate contaminated red soil by Gordonia terrae RL-JC02: Characterization, metabolic pathway and kinetics

Di-(2-ethylhexyl) phthalate (DEHP) is the most widely used plasticizer and a representative endocrine disrupting chemical. The toxicological effects of DEHP on environmental and human health have been widely investigated. In this study, the DEHP-degrading bacterial strain RL-JC02 was isolated from red soil with long-term usage of plastic mulch, and it was identified as Gordonia terrae by 16S rRNA gene analysis coupled with physiological and biochemical characterization. The biodegrading capacity of different phthalic acid esters and related intermediates was investigated as well as the performance of strain RL-JC02 under different environmental conditions, such as temperature, pH, salinity and DEHP concentration. Specifically, strain RL-JC02 showed good tolerance to low pH, with 86.6% of DEHP degraded under the initial pH of 5.0 within 72 h. The metabolic pathway of DEHP was examined by metabolic intermediate identification via a high-performance liquid chromatography coupled with mass spectrometry (HPLC-MS) analysis in which DEHP was hydrolyzed into phthalic acid (PA) and 2-ethylhexanol (2-EH) via mono (2-ethylhexyl) phthalate (MEHP). PA and 2-EH were further utilized through the protocatechuic acid metabolic pathway and β-oxidation via protocatechuic acid and 2-ethylhexanoic acid, respectively. The application potential of strain RL-JC02 was confirmed through the bioremediation of artificial DEHP-contaminated red soil showing 91.8% DEHP degradation by strain RL-JC02 within 30 d. The kinetics analysis of DEHP degradation by strain RL-JC02 in soil demonstrated that the process followed the modified Gompertz model. Meanwhile, the cell concentration monitoring of strain RL-JC02 in soil with absolute quantification polymerase chain reaction (qPCR) suggested that strain RL-JC02 survived well during bioremediation. This study provides sufficient evidence of a robust degrader for the bioremediation of PAE-contaminated red soil.

Spatial distribution of phthalate esters and the associated response of enzyme activities and microbial community composition in typical plastic-shed vegetable soils in China

The widespread use of phthalate esters (PAEs) in plastic products has made them ubiquitous in environment. In this study, 93 soil samples were collected in 31 plastic-sheds from one of China's largest vegetable production bases, Shouguang City, Shandong Province, to investigate the pollution characteristics and composition of PAEs in soils. Eleven PAEs were detected in the soil samples with the total concentration of 756-1590 μg kg^-1 dry soil. Di (2-ethylhexyl) phthalate (DEHP), bis (2-n-butoxyethyl) phthalate (DBEP), di-isobutyl phthalate (DiBP) and di-n-butyl phthalate (DBP) were the main pollutants with the highest concentrations. Moreover, soil properties, including pH, total organic carbon (TOC), soil enzyme activities, and soil microbial community characteristics, were monitored to explore the associated formation mechanisms. The concentration of PAEs in the plastic-shed vegetable soils was regionalized and the contamination degree in different regions was related to soil microbial characteristics and soil enzyme activities. Phthalate ester is positively correlated with catalase and sucrase, and negatively correlated with dehydrogenase and urease. Furthermore, some tolerant and sensitive bacteria were selected, which possibly could be used as potential indicators of PAE contamination in soil. Dimethyl phthalate (DMP) and DBP also had greater effects on the soil microbial community than other PAEs. The results will provide essential data and support the control of PAEs in plastic-shed vegetable soils in China.

Biodegradation of High Concentrations of Aliphatic Hydrocarbons in Soil from a Petroleum Refinery: Implications for Applicability of New Actinobacterial Strains

At present, there is great demand for new resistant and metabolically active strains of biodegrading bacteria capable of degrading high concentrations of petroleum pollutants. In this study, we undertook a series of pot-based biodegradation experiments on soil from a petroleum refinery lagoon heavily polluted with aliphatic hydrocarbons (81.6 ± 2.5 g·kg−1 dry weight) and metals. Periodical bioaugmentation with either a mixture of isolated degraders identified as Bacillus sp. and Ochrobactrum sp. or biostimulation with nutrient medium, singly or in combination, did not produce any significant decrease in hydrocarbons, even after 455 days. Inoculation with Gordonia rubripertincta CWB2 and Rhodococcus erythropolis S43 in iron-limited media, however, resulted in a significant decrease in hydrocarbons 45 days after bioaugmentation. These actinobacterial strains, therefore, show significant potential for bioremediation of such highly polluted soils.

Excellent Degradation Performance of a Versatile Phthalic Acid Esters-Degrading Bacterium and Catalytic Mechanism of Monoalkyl Phthalate Hydrolase

Despites lots of characterized microorganisms that are capable of degrading phthalic acid esters (PAEs), there are few isolated strains with high activity towards PAEs under a broad range of environmental conditions. In this study, Gordonia sp. YC-JH1 had advantages over its counterparts in terms of di(2-ethylhexyl) phthalate (DEHP) degradation performance. It possessed an excellent degradation ability in the range of 20–50 °C, pH 5.0–12.0, or 0–8% NaCl with the optimal degradation condition 40 °C and pH 10.0. Therefore, strain YC-JH1 appeared suitable for bioremediation application at various conditions. Metabolites analysis revealed that DEHP was sequentially hydrolyzed by strain YC-JH1 to mono(2-ethylhexyl) phthalate (MEHP) and phthalic acid (PA). The hydrolase MphG1 from strain YC-JH1 hydrolyzed monoethyl phthalate (MEP), mono-n-butyl phthalate (MBP), mono-n-hexyl phthalate (MHP), and MEHP to PA. According to molecular docking and molecular dynamics simulation between MphG1 and monoalkyl phthalates (MAPs), some key residues were detected, including the catalytic triad (S125-H291-D259) and the residues R126 and F54 potentially binding substrates. The mutation of these residues accounted for the reduced activity. Together, the mechanism of MphG1 catalyzing MAPs was elucidated, and would shed insights into catalytic mechanism of more hydrolases.