Metabolism of diethyl phthalate (DEP) and identification of degradation intermediates by Pseudomonas sp. DNE-S1

Study on the mechanism and degradation behavior of Encifer adhaerens DNM-S1 capturing dimethyl phthalate

The global concern surrounding pollution caused by phthalates is escalating, with dimethyl phthalate (DMP) emerging as one of the most prevalent contaminants within the phthalates (PAEs) category. Although the biodegradation of DMP is considered both safe and efficient, its underlying degradation mechanism is not yet fully elucidated, and the degradation performance can be somewhat inconsistent. To address this issue, our study isolated a DMP-degrading bacterium (DNM-S1) from a vegetable greenhouse. The resulting data revealed that DNM-S1 exhibited a remarkable degradation performance, successfully degrading 84.98% of a 2000 mg L-1 DMP solution within 72 h. Remarkably, it achieved complete degradation of a 50 mg L-1 DMP solution within just 3 h. DMP degradation by DNM-S1 was also found to be efficient even under low-temperature conditions (10 °C). Our research further indicates that DNM-S1 is capable of capturing DMP through the ester bond in the bacterium's cell wall fatty acids, forming hydrogen bonds through hydrophobic interactions. The DMP was then transported into the DNM-S1 protoplasm using an active transport mechanism. Interestingly, the secondary metabolites of DNM-S1 contained natural carotenoids, which could potentially counteract the damaging effects of PAEs on cell membrane permeability. In summary, these findings highlight the potential of DNM-S1 in addressing PAEs pollution and provide new insights into the metabolic mechanism of PAEs degradation.

Molecular insights into the catabolism of dibutyl phthalate in Pseudomonas aeruginosa PS1 based on biochemical and multi-omics approaches

A comprehensive understanding of the molecular mechanisms underlying microbial catabolism of dibutyl phthalate (DBP) is still lacking. Here, we newly isolated a bacterial strain identified as Pseudomonas aeruginosa PS1 with high efficiency of DBP degradation. The degradation ratios of DBP at 100-1000 mg/L by this strain reached 80-99 % within 72 h without a lag phase. A rare DBP-degradation pathway containing two monobutyl phthalate-catabolism steps was proposed based on intermediates identified by HPLC-TOF-MS/MS. In combination with genomic and transcriptomic analyses, we identified 66 key genes involved in DBP biodegradation and revealed the genetic basis for a new complete catabolic pathway from DBP to Succinyl-CoA or Acetyl-CoA in the genus Pseudomonas for the first time. Notably, we found that a series of homologous genes in Pht and Pca clusters were simultaneously activated under DBP exposure and some key intermediate degradation related gene clusters including Pht, Pca, Xyl, Ben, and Cat exhibited a favorable coexisting pattern, which contributed the high-efficient DBP degradation ability and strong adaptability to this strain. Overall, these results broaden the knowledge of the catabolic diversity of DBP in microorganisms and enhance our understanding of the molecular mechanism underlying DBP biodegradation.

Dibutyl phthalate degradation by Paenarthrobacter ureafaciens PB10 through downstream product myristic acid and its bioremediation potential in contaminated soil

Dibutyl phthalate (DBP) is a widely used plasticizer to make plastic flexible and long-lasting. It is easily accessible in a broad spectrum of environments as a result of the rising level of plastic pollution. This compound is considered a top-priority toxicant and persistent organic pollutant by international environmental agencies for its endocrine disruptive and carcinogenic propensities. To mitigate the DBP in the soil, one DBP-degrading bacterial strain was isolated from a plastic-polluted landfill and identified as Paenarthrobacter ureafaciens PB10 by 16S rRNA gene sequence-based homology. The strain was found to develop a distinct transparent halo zone around grown colonies on an agar plate supplemented with DBP. The addition of yeast extract (100 mg/L) as a nutrient source accelerated cell biomass production and DBP degradation rate; however, the presence of glucose suppressed DBP degradation by the PB10 strain without affecting its ability to proliferate. The strain PB10 was efficient in eliminating DBP under various pH conditions (5.0-8.0). Maximum cell growth and degradation of 99.49% at 300 mg/L DBP were achieved in 72 h at the optimized mineral salt medium (MS) conditions of pH 7.0 and 32 °C. Despite that, when the concentration of DBP rose to 3000 mg/L, the DBP depletion rate was measured at 79.34% in 72 h. Some novel intermediate metabolites, like myristic acid, hexadecanoic acid, stearic acid, and the methyl derivative of 4-hydroxyphenyl acetate, along with monobutyl phthalate and phthalic acid, were detected in the downstream degradation process of DBP through GC-MS profiling. Furthermore, in synchronization with native soil microbes, this PB10 strain successfully removed a notable amount of DBP (up to 54.11%) from contaminated soil under microcosm study after 10 d. Thus, PB10 has effective DBP removal ability and is considered a potential candidate for bioremediation in DBP-contaminated sites.

Assessment of the UV/DCCNa and UV/NaClO oxidation process for the removal of diethyl phthalate (DEP) in the aqueous system

In this work, the removal and transformation process of diethyl phthalate (DEP) in UV/dichloroisocyanurate (UV/DCCNa) and UV/sodium hypochlorite (UV/NaClO) systems were compared to evaluate the application potential of UV/DCCNa technology. Compared with UV/NaClO, UV/DCCNa process has the advantage of DEP removal and caused a higher degradation efficiency (93.8%) within 45 min of oxidation in ultrapure water due to the sustained release of hypochloric acid (HOCl). Fourteen intermediate products were found by high-resolution mass spectrometry, and the transformation patterns including hydroxylation, hydrolysis, chlorination, cross-coupling, and nitrosation were proposed. The oxidation processes were also performed under quasi-realistic environmental conditions, and it was found that DEP could be effectively removed in both systems, with yields of disinfection byproduct meeting the drinking water disinfection standard (<60.0 μg/L). Comparing the single system, the removal of DEP decreased in the mixed system containing five kinds of PAEs, which could be attributed to the regeneration of DEP and the competitive effect of •OH occurred among the Dimethyl phthalate (DMP), DEP, Dipropyl phthalate (DPrP), Diallyl phthalate (DAP) and Diisobutyl phthalate (DiBP). However, a greater removal performance presented in UV/DCCNa system compared with UV/NaClO system (69.4% > 62.1%). Further, assessment of mutagenicity and developmental toxicity by Toxicity Estimation Software Tool (T.E.S.T) software indicated that UV/DCCNa process has fewer adverse effects on the environment and is a more environmentally friendly chlorination method. This study may provide some guidance for selecting the suitable disinfection technology for drinking water treatment.

Influence of leachate microenvironment on the occurrence of phthalate esters in landfills

Phthalate esters (PAEs) are added to various products as plasticizers. Plastic waste containing PAEs enters landfills as they age with use. However, the influence of microenvironmental changes on the occurrence of PAEs during landfill stabilization is still unknown. In this study, we evaluated the relationship between the physical and chemical properties of leachate, the structure of bacterial communities and the chemical structure of dissolved organic matter (DOM), and the occurrence of PAEs and the mechanism underlying their responses to changes. Landfill leachate in different stabilization states had high Cl- and NH4+ contents and its metal element (Cr, Pb, and Zn) contents generally decreased with the increase in landfill ages. Proteobacteria, Bacteroidetes, and Firmicutes were important phyla and had an average relative abundance of 68.63%. The lignin/carboxylate-rich alicyclic molecule structure was the main component of DOM (56%-64%). Of the 6-priority controlled PAEs in leachate, di-n-butyl phthalate was the most abundant (1046 μg L-1), while butyl phthalate was not detected. The results showed that pH, the relative abundance of Chloroflexi, and the value of SUVA254 can directly influence the occurrence of PAEs in leachate. The positive and negative effects vary depending on the PAE content and molecular weight. DBP and DEHP have higher environmental risks in the aquatic system. These results are intended to provide a scientific basis for the evolutionary characterization of the microenvironment in complex environmental systems and the control of novel contaminants, such as PAEs.

Natural surfactant mediated bioremediation approaches for contaminated soil

The treatment of environmental pollution by employing microorganisms is a promising technology, termed bioremediation, which has several advantages over the other established conventional remediation techniques. Consequently, there is an urgent inevitability to develop pragmatic techniques for bioremediation, accompanied by the potency of detoxifying soil environments completely. The bioremediation of contaminated soils has been shown to be an alternative that could be an economically viable way to restore polluted soil. The soil environments have long been extremely polluted by a number of contaminants, like agrochemicals, polyaromatic hydrocarbons, heavy metals, emerging pollutants, etc. In order to achieve a quick remediation overcoming several difficulties the utility of biosurfactants became an excellent advancement and that is why, nowadays, the biosurfactant mediated recovery of soil is a focus of interest to the researcher of the environmental science field specifically. This review provides an outline of the present scenario of soil bioremediation by employing a microbial biosurfactant. In addition to this, a brief account of the pollutants is highlighted along with how they contaminate the soil. Finally, we address the future outlook for bioremediation technologies that can be executed with a superior efficiency to restore a polluted area, even though its practical applicability has been cultivated tremendously over the few decades.

Whole-genome analysis of Comamonas sp. USTBZA1 for biodegrading diethyl phthalate

Extensive use of phthalic acid esters (PAEs) as plasticizer causes diffusion into the environment, which posed a great threat to mankind. It was reported that Comamonas sp. was a potentially robust aromatic biodegrader. Although the biodegradation of several PAEs by Comamonas sp. was studies, the comprehensive genomic analysis of Comamonas sp. was few reported. In the present study, one promising bacterial strain for biodegrading diethyl phthalate (DEP) was successfully isolated from activated sludge and characterized as Comamonas sp. USTBZA1 based on the 16S rRNA sequence analysis. The results showed that pH 7.5, 30 °C and inoculum volume ratio of 6% were optimal for biodegradation. Initial DEP of 50 mg/L could be completely biodegrade by strain USTBZA1 within 24 h which conformed to the Gompertz model. Based on the Q-TOF LC/MS analysis, monoethyl phthalate (MEP) and phthalic acid (PA) were identified as the metabolic products of DEP biodegradation by USTBZA1. Furthermore, the whole genome of Comamonas sp. USTBZA1 was analyzed to clarify the molecular mechanism for PAEs biodegradation by USTBZA1. There were 3 and 41 genes encoding esterase/arylesterase and hydrolase, respectively, and two genes regions (pht34512 and pht4253) were responsible for the conversion of PA to protocatechuate (PCA), and two genes regions (ligCBAIKJ) were involved in PCA metabolism in USTBZA1. These results substantiated that Comamonas sp. USTBZA1 has potential application in the DEP bioremediation.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13205-023-03736-3.

Full life cycle and sustainability transitions of phthalates in landfill: A review

Phthalates (PAEs) are added to various products as a plasticizer. As these products age and are disposed of, plastic waste containing PAEs enters the landfill. The landfill environment is complicated and can be regarded as a "black box". Also, PAEs do not bind with the polymer matrix. Therefore, when a series of physical chemistry and biological reactions occur during the stabilization of landfills, PAEs leach from waste and migrate to the surrounding environmental media, thereby contaminating the surrounding soil, water ecosystems, and atmosphere. Although research on PAEs has achieved progress over the years, they are mainly concentrated on a particular aspect of PAEs in the landfill; there are fewer inquiries on the life cycle of PAEs. In this study, we review the presence of PAEs in the landfill in the following aspects: (1) the main source of PAEs in landfills; (2) the impact of the landfill environment on PAE migration and conversion; (3) distribution and transmedia migration of PAEs in aquatic ecosystems, soils, and atmosphere; and (4) PAE management and control in the landfill and future research direction. The purpose is to track the life cycle of PAEs in landfills, provide scientific basis for in-depth understanding of the migration and transformation of PAEs and environmental pollution control in landfills, and new ideas for the sustainable utilization of landfills.

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.

Evaluation of distinct molecular architectures and coordinated regulation of the catabolic pathways of oestrogenic dioctyl phthalate isomers in Gordonia sp

Bacterial strain GONU, belonging to the genus Gordonia, was isolated from a municipal waste-contaminated soil sample and was capable of utilizing an array of endocrine-disrupting phthalate diesters, including di-n-octyl phthalate (DnOP) and its isomer di(2-ethylhexyl) phthalate (DEHP), as the sole carbon and energy sources. The biochemical pathways of the degradation of DnOP and DEHP were evaluated in strain GONU by using a combination of various chromatographic, spectrometric and enzymatic analyses. Further, the upregulation of three different esterases (estG2, estG3 and estG5), a phthalic acid (PA)-metabolizing pht operon and a protocatechuic acid (PCA)-metabolizing pca operon were revealed based on de novo whole genome sequence information and substrate-induced protein profiling by LC-ESI-MS/MS analysis followed by differential gene expression by real-time PCR. Subsequently, functional characterization of the differentially upregulated esterases on the inducible hydrolytic metabolism of DnOP and DEHP revealed that EstG5 is involved in the hydrolysis of DnOP to PA, whereas EstG2 and EstG3 are involved in the metabolism of DEHP to PA. Finally, gene knockout experiments further validated the role of EstG2 and EstG5, and the present study deciphered the inducible regulation of the specific genes and operons in the assimilation of DOP isomers.

Global Situation of Bioremediation of Leachate-Contaminated Soils by Treatment with Microorganisms: A Systematic Review

This systematic review presents the current state of research in the last five years on contaminants in soils, especially in leachates from solid waste landfills, with emphasis on biological remediation. In this work, the pollutants that can be treated by microorganisms and the results obtained worldwide were studied. All the data obtained were compiled, integrated, and analyzed by soil type, pollutant type, bacterial type, and the countries where these studies were carried out. This review provides reliable data on the contamination of soils worldwide, especially soils contaminated by leachate from municipal landfills. The extent of contamination, treatment objectives, site characteristics, cost, type of microorganisms to be used, and time must be considered when selecting a viable remediation strategy. The results of this study can help develop innovative and applicable methods for evaluating the overall contamination of soil with different contaminants and soil types. These findings can help develop innovative, applicable, and economically feasible methods for the sustainable management of contaminated soils, whether from landfill leachate or other soil types, to reduce or eliminate risk to the environment and human health, and to achieve greater greenery and functionality on the planet.

Biodegradation of diethyl phthalate and phthalic acid by a new indigenous Pseudomonas putida

Diethyl phthalate (DEP) is one of the extensively used plasticizers which has been considered a priority hazardous pollutant due to its carcinogenic, endocrine disrupter, and multi-toxic effects on humans. The identification of DEP in different parts of the ecosphere has increased the global community's attention to the elimination of this pollutant in a bio-eco-friendly way. In this research, a novel aerobic bacterial strain nominates as ShA (GenBank accession number: MN298858) capable of consuming DEP as carbon and energy sources, was isolated from the upper phase (0-10 cm) of Anzali international wetland sediments by enrichment culture method. Morphological characteristics and 16S rRNA gene sequence analysis demonstrated that strain ShA belonged to Pseudomonas putida. The substrate utilization test demonstrated that strain ShA was able to grow in mineral salt medium containing dimethyl phthalate (DMP) and phthalic acid (PA) isomers including terephthalic and isophthalic acid. Degradation assay showed strain ShA completely degraded 200 mg/L DEP within 22 h (pH 7.0, 30 °C). Surprisingly, PA as the main intermediate of DEP biodegradation was identified by GC-FID. Moreover, the rapid degradation of 2000 mg/L PA to CO₂ and H₂O was viewed in 22 h by strain ShA. The possible route of DEP degradation was DEP directly to PA and then PA consumption for growth. This study obtained results that provide a great contribution to applying strain ShA in the biodegradation of low molecular weight of PAEs and PA isomers in natural ecosystems. This is the first report of a P. putida strain able to degrade DEP and PA.

Development of multifarious carrier materials and impact conditions of immobilised microbial technology for environmental remediation: A review

Microbial technology is the most sustainable and eco-friendly method of environmental remediation. Immobilised microorganisms were introduced to further advance microbial technology. In immobilisation technology, carrier materials distribute a large number of microorganisms evenly on their surface or inside and protect them from external interference to better treat the targets, thus effectively improving their bioavailability. Although many carrier materials have been developed, there have been relatively few comprehensive reviews. Therefore, this paper summarises the types of carrier materials explored in the last ten years from the perspective of structure, microbial activity, and cost. Among these, carbon materials and biofilms, as environmentally friendly functional materials, have been widely applied for immobilisation because of their abundant sources and favorable growth conditions for microorganisms. The novel covalent organic framework (COF) could also be a new immobilisation material, due to its easy preparation and high performance. Different immobilisation methods were used to determine the relationship between carriers and microorganisms. Co-immobilisation is particularly important because it can compensate for the deficiencies of a single immobilisation method. This paper emphasises that impact conditions also affect the immobilisation effect and function. In addition to temperature and pH, the media conditions during the preparation and reaction of materials also play a role. Additionally, this study mainly reviews the applications and mechanisms of immobilised microorganisms in environmental remediation. Future development of immobilisation technology should focus on the discovery of novel and environmentally friendly carrier materials, as well as the establishment of optimal immobilisation conditions for microorganisms. This review intends to provide references for the development of immobilisation technology in environmental applications and to further the improve understanding of immobilisation technology.

Compound-specific isotopic analysis to characterize the photocatalytic reaction of TiO2 nanoparticles with diethyl phthalate

In this study compound-specific isotope analysis (CSIA) has been used to explore the degradation mechanism of nano titanium dioxide (TiO₂) catalyzes photodegradation of diethyl phthalate (DEP). TiO₂ is a popular photosensitizer with potential in waste water treatment and application in advanced oxidation processes. The degradation process of DEP can be described with a first-order kinetics in the applied concentration ranges. The larger degradation rate constant has been found at neutral conditions. The ¹³C and ²H isotope fractionation associated with the nano TiO₂ catalyzes photodegradation of DEP at pH 3, 7 and 11 yield normal isotope effects. In the TiO₂/UV/DEP and TiO₂/H₂O₂/UV/DEP systems, the correlation of ¹³C and ²H fractionation (Λ) were calculated to be 2.7 ± 0.2, 2.8 ± 0.2 at pH 3, 2.2 ± 0.4, 2.5 ± 0.2, 2.3 ± 0.6 at pH 7 and 2.6 ± 0.3, 2.2 ± 0.3, 2.7 ± 0.2 and 2.3 ± 0.3 at pH11, respectively. The dominant free radical species in studied systems were explored by combining free radical quenching method and electron paramagnetic resonance analysis. The hydroxyl radicals have been found as the main radical species at all pH conditions studied. Furthermore, the ¹³C and ²H fractionation suggested that the addition of •OH on the benzene ring of DEP is the main conversion pathway. Therefore, CSIA is a promising technology for the identification of reaction pathways of DEP for example in water treatment systems.

Phthalates - A family of plasticizers, their health risks, phytotoxic effects, and microbial bioaugmentation approaches

Phthalates are a family of reprotoxicant compounds, predominantly used as a plasticizer to improve the flexibility and longevity of consumable plastic goods. After their use these plastic products find their way to the waste disposal sites where they leach out the hazardous phthalates present within them, into the surrounding environment, contaminating soil, groundwater resources, and the nearby water bodies. Subsequently, phthalates move into the living system through the food chain and exhibit the well-known phenomenon of biological magnification. Phthalates as a primary pollutant have been classified as 1B reprotoxicants and teratogens by different government authorities and they have thus imposed restrictions on their use. Nevertheless, the release of these compounds in the environment is unabated. Bioremediation has been suggested as one of the ways of mitigating this menace, but studies regarding the field applications of phthalate utilizing microbes for this purpose are limited. Through this review, we endeavor to make a deeper understanding of the cause and concern of the problem and to find out a possible solution to it. The review critically emphasizes the various aspects of phthalates toxicity, including their chemical nature, human health risks, phytoaccumulation and entry into the food chain, microbial role in phthalate degradation processes, and future challenges.

Role of plant growth-promoting rhizobacteria in boosting the phytoremediation of stressed soils: Opportunities, challenges, and prospects

Soil is considered as a vital natural resource equivalent to air and water which supports growth of the plants and provides habitats to microorganisms. Changes in soil properties, productivity, and, inevitably contamination/stress are the result of urbanisation, industrialization, and long-term use of synthetic fertiliser. Therefore, in the recent scenario, reclamation of contaminated/stressed soils has become a potential challenge. Several customized, such as, physical, chemical, and biological technologies have been deployed so far to restore contaminated land. Among them, microbial-assisted phytoremediation is considered as an economical and greener approach. In recent decades, soil microbes have successfully been used to improve plants' ability to tolerate biotic and abiotic stress and strengthen their phytoremediation capacity. Therefore, in this context, the current review work critically explored the microbial assisted phytoremediation mechanisms to restore different types of stressed soil. The role of plant growth-promoting rhizobacteria (PGPR) and their potential mechanisms that foster plants' growth and also enhance phytoremediation capacity are focussed. Finally, this review has emphasized on the application of advanced tools and techniques to effectively characterize potent soil microbial communities and their significance in boosting the phytoremediation process of stressed soils along with prospects for future research.

Mass balance and kinetics of biodegradation of endocrine disrupting phthalates by Cellulosimicrobium funkei in a continuous stirred tank reactor system

This study investigated the potential ofCellulosimicrobium funkeifor degrading dimethyl phthalate (DMP) and diethyl phthalate (DEP). Effect of different initial concentrations of phthalates on their biodegradation and growth ofC. funkeiwas examined using shake flasks and a continuous stirred tank reactor (CSTR). Complete degradation of both DMP and DEP was achieved in CSTR, even up to 3000 and 2000 mg/L initial concentrations, respectively. Simultaneous degradation of the phthalates in mixture, i.e. more than 80% and 55% biodegradation efficiency were achieved at 1000 and 2000 mg/L initial concentrations of DMP and DEP, respectively, using the CSTR. Mass balance analysis of the degradation results suggested proficient degradation of DMP and DEP with biomass yield values of 0.64 and 0.712, respectively. The high values of inhibition constant Kiestimated using the Tessier and Edward substrate inhibition models indicated very good tolerance ofC. funkeitoward biodegradation of DMP and DEP.

Contrasting impacts of drying-rewetting cycles on the dissipation of di-(2-ethylhexyl) phthalate in two typical agricultural soils

Di-(2-ethylhexyl) phthalate (DEHP) pollution has become a growing problem in farmlands of China. Drying-rewetting (DW) cycle is one of frequent environmental changes that agricultural production is confronted with, and also a convenient and practical agronomic regulation measure. In this study, in order to explore the effects of DW cycles on the dissipation of DEHP and their driving mechanisms in different types of soils, we performed a 45-day microcosm culture experiment with two typical agricultural soils, Lou soil (LS) and Red soil (RS). High-throughput sequencing was applied to study the response of soil microbial communities in the process of DEHP dissipation under DW cycles. The results showed that the DW cycles considerably inhibited the dissipation of DEHP in LS while promoted that in RS. The DW cycles obviously decreased the diversity, the relative abundance of significantly differential bacteria, and the total abundance of potential degrading bacterial groups in LS, whereas have little effect on bacterial community in RS, except at the initial cultivation stage when the corresponding parameters were promoted. The inhibition of the DW cycles on DEHP dissipation in LS was mainly derived from microbial degradation, but the interplay between microbial functions and soil attributes contributed to the promotion of DEHP dissipation in RS under the DW cycles. This comprehensive understanding of the contrasting impacts and underlying driving mechanisms may provide crucial implications for the prevention and control of DEHP pollution in regional soils.

Simultaneous removal of nitrate and diethyl phthalate using a novel sponge-based biocarrier combined modified walnut shell biochar with Fe3O4 in the immobilized bioreactor

A novel biological carrier combining sponge and modified walnut shell biochar with Fe₃O₄ (MWSB@Fe₃O₄) was fabricated to achieve simultaneous removal of nitrate and diethyl phthalate (DEP). The optimal reaction conditions of the immobilized bioreactor were: carbon to nitrogen (C/N) ratio of 1.5, Fe²⁺ concentration of 20 mg L^-1, and hydraulic retention time (HRT) of 8 h. Under the optimal conditions and DEP concentration of 800 μg L^-1, the highest removal efficiency of DEP and nitrate in the immobilized bioreactor with the novel biological carrier were 67.87% and 83.97% (68.43 μg L^-1 h^-1 and 1.71 mg L^-1 h^-1), respectively. Scanning electron microscopy (SEM) showed that the novel biological carrier in this study carried more bio-sediments which is closely related to the denitrification efficiency. The gas chromatography (GC) data showed that the nitrogen production of the immobilized bioreactor (99.85%) was higher than that of another experimental group (97.84%). Fluorescence excitation-emission matrix (EEM) and Fourier transform infrared spectrometer (FTIR) indicated the immobilized bioreactor emerged more extracellular polymeric substances (EPS) which was related to favourable biological stability under the DEP environment. Moreover, according to high-throughput sequencing data, the Zoogloea sp. L2 responsible for iron-reduction and denitrification was the main strain in this immobilized bioreactor.

Complete biodegradation of di-n-butyl phthalate (DBP) by a novel Pseudomonas sp. YJB6

Phthalate acid esters (PAEs) are environmentally ubiquitous and have aroused a worldwide concern due to their threats to environment and human health. Di-n-butyl phthalate (DBP) is one of the most frequently observed PAEs in the environment. In this study, a novel bacterium identified as Pseudomonas sp. YJB6 that isolated from PAEs-contaminated soil was determined to have strong DBP-degrading activity. A complete degradation of DBP in 200 mg/L was achieved within 3 days when YJB6 was cultivated at 31.4 °C with an initial inoculation size of 0.6 (OD600) in basic mineral salts liquid medium (MSM), pH 7.6. The degradation curves of DBP (50-2000 mg/L) fitted well the first-order kinetics model, with a half-life (t_1/2) ranging from 0.86 to 1.88 d. The main degradation intermediates were identified as butyl-ethyl phthalate (BEP), mono-butyl phthalate (MBP), phthalic acid (PA) and benzoic acid (BA), indicating a new complex and complete biodegradation pathway presented by YJB6. DBP might be metabolized through de-esterification, β-oxidation, and hydrolysis, followed by entering the Krebs cycle of YJB6 as a final step. Strain YJB6 was successfully immobilized with sodium alginate (SA), polyvinyl alcohol (PVA), and SA-PVA. The immobilization significantly improved the stability and adaptability of the cells thus resulting in high volumetric DBP-degrading rates compared to that of the freely suspended cells. In addition, these immobilized cells can be reused for many cycles with well conserved in DBP-degrading activity. The ideal DBP degrading ability of the free and immobilized YJB6 cells suggests that strain YJB6, especially the SA-PVA+ YJB6 promises great potential to remove hazardous PAEs.

Biostimulation of Rhodovulum sp., for enhanced degradation of di-n-butyl phthalate under optimum conditions

Di-butyl phthalate (DBP) is an extensively applied synthetic plasticizer, toxic organic compound with elevated concentrations in aquatic and terrestrial ecosystem that cause serious risk to the human health. A marine bacterium Rhodovulum sp. DBP07 isolated from sea water with proficient of efficiently degrading DBP. The maximum DBP degradation (70.2%) and the cell growth (1.3 OD_600nm) were observed at 600 mg/L. The DBP degradation characteristics of the isolate Rhodovulum sp. DBP07 with diverse preliminary concentrations of DBP was found to be 200 ˃ 400 ˃ 600 ˂ 800 ˂ 1000 mg/L DBP. Glucose was identified as most favorable nutrient factor for the enhanced growth and showed 79.8 and 77.4% of degradation rate at 5.0 and 2.0 g/L respectively. The influence of the carbon sources on DBP degradation was found to be Glucose ˃ fructose ˃ sucrose ˃ maltose ˃ lactose ˃ citric acid ˃ starch. Box-Behnken (BBD) statistical optimization results showed enhanced DBP biodegradation rate (91.1%) at pH 7.0, 3% of NaCl concentration with 3 days of incubation. Two intermediate compounds were observed in the retention times of 10.8 and 12.2 which are identified as diethyl phthalate (DEP) and mono-nbutyl phthalate (MBP) using Gas chromatography mass spectroscopy (GC-MS). Furthermore, the phthalate (pht) gene expression pattern under DBP stress was analyzed using RT-qPCR and the maximum fold change (5.7 fold) was observed at 3 day of incubation. Overall, the observed results indicate the possibility of utilizing Rhodovulum sp. for remediation of DBP contaminated environment.

An efficient phthalate ester-degrading Bacillus subtilis: Degradation kinetics, metabolic pathway, and catalytic mechanism of the key enzyme

Phthalate ester pollution in the environment and food chain is frequently reported. Microbial treatment is a green and efficient method for solving this problem. The isolation and systematic investigation of microorganisms generally recognized as safe (GRAS) will provide useful resources. A GRAS Bacillus subtilis strain, BJQ0005, was isolated from Baijiu fermentation starter and efficiently degraded phthalate esters (PAEs). The half-lives for di-isobutyl phthalate, di-butyl phthalate and di-(2-ethylhexyl) phthalate were 3.93, 4.28, and 25.49 h, respectively, from the initial amount of 10 mg per 10 mL reaction mixture, which are records using wild-type strains. Genome sequencing and metabolic intermediate analysis generated the whole metabolic pathway. Eighteen enzymes from the α/β hydrolase family were expressed. Enzymes GTW28_09400 and GTW28_13725 were capable of single ester bond hydrolysis of PAEs, while GTW28_17760 hydrolyzed di-ester bonds of PAEs. Using molecular docking, a possible mechanism affecting enzymatic ester bond hydrolysis of mono-butyl phthalate was proposed of GTW28_17760. The carboxyl group generated by the first hydrolysis step interacted with histidine in the catalytic active center, which negatively affected enzymatic hydrolysis. Isolation and systematic investigation of the PAE degradation characteristics of B. subtilis will promote the green and safe treatment of PAEs in the environment and food industry.

Biodegradation of diethyl-phthalate (DEP) by halotolerant bacteria isolated from an estuarine environment

Phthalates are widely used as plasticizers in many industrial products due to their chemical properties that confer flexibility and durability to building materials, lubricants, solvents, insect repellents, clothing, cosmetics, being widely distributed in the environment. Besides persistent, they are also considered endocrine-disrupting compounds (EDCs), causing a global concern about their release into the environment, once they can alter the reproductive and endocrine health of humans systems. Under natural conditions, photodegradation and hydrolysis rates of phthalates are often very slow; therefore, microbial degradation is a natural way to treat these pollutants. In this context, three bacterial consortia (CMS, GMS and GMSS) were isolated from environmental samples from the Santos Estuarine System (SES) and were able to grow on diethyl-phthalate (DEP) as an only carbon source. From the GMSS consortium, three different strains were isolated and identified as Burkholderia cepacia, Pseudomonas koreensis and Ralstonia pickettii by molecular and mass spectrometry (MALDI-TOF-Biotyper) techniques. Considering there are no reports about Ralstonia genus on phthalates degradation, this strain was chosen to proceed the kinetics experiments. Ralstonia pickettii revealed a great ability to degrade DEP (300 mg/L) in less than 24 h. This is the first report implicating R. pickettii in DEP degradation.

Uptake, translocation and metabolism of di-n-butyl phthalate in alfalfa (Medicago sativa)

Uptake and metabolism by plants are important biotransformation processes of organic pollutants in ecosystems. However, very limited information is currently available on the metabolism of phthalic acid esters (PAEs) in plants. In this study, alfalfa, highly efficient in phytoremediation of PAE contaminated soil, was chosen as the model to understand the fate of di-n-butyl phthalate (DnBP) in remediation plant. The results of hydroponic experiments indicated that DnBP accumulated mainly in alfalfa roots and adsorption to root epidermis might be the primary uptake mechanism. A large proportion of DnBP was subjected to apparent metabolism. De-esterification could be specified to be the predominant metabolism pathway. Mono-n-butyl phthalate (MnBP) and phthalic acid (PA) were detected as DnBP metabolites in all alfalfa roots and shoots throughout the entire exposure period. Around >90% of MnBP were distributed in cell soluble components and organelles, and MnBP gradually transferred from organelles and cell walls to soluble components as the exposure time extended. Similar to MnBP, PA located mainly in soluble components and organelles as well, while no PA existed in alfalfa cell walls. Exposure to DnBP ultimately resulted in the coexistence of DnBP and MnBP for a long term in interior plants, raising concerns on their combined potential toxicity on plant health or even ecosystem.

Anthraquinone-2,6-disulfonate enhanced biodegradation of dibutyl phthalate: Reducing membrane damage and oxidative stress in bacterial degradation

Plasticizer dibutyl phthalate (DBP) pollution has received more and more attention. In this study, a DBP degrading bacteria Enterobacter sp. DNB-S2 was found to suffer membrane damage and oxidative stress during DBP degradation. Physiological and transcriptome analysis showed that 100 μmol L^-1 anthraquinone-2,6-disulfonate (AQDS) could enhance the ability of strain DNB-S2 for biodegradation of DBP. AQDS adjusted the cell surface structure, including increase levels of hydrophobic and unsaturated fatty acids. These changes increased the chemotactic ability of the strain DNB-S2 to the hydrophobic pollutant DBP and the fluidity of the cell membrane. The expression of methyl chemotactic protein and genes associated with cell membrane-fixed components were up-regulated. AQDS also improved the scavenging ability of ·OH and H₂O₂ of DNB-S2 by promoting expression genes related to glutathione metabolism, thereby reducing oxidative stress. These results will provide new insights into the biodegradation of DBP.

Carbaryl waste-water treatment by Rhodopseudomonas sphaeroides

Carbaryl wastewater treatment and the resource recycling of biomass as sludge by Rhodopseudomonas sphaeroides (R. sphaeroides) with the assistance of starch processing wastewater (SPW) was investigated in this research. It was observed that carbaryl was not degraded under the 100, 500 mg/L COD groups. The addition of SPW assisted R. sphaeroides to degrade carbaryl efficiently. Carbaryl removal reached 100% after 5 days under the optimal group (3500 mg/L). Interestingly, carbaryl in the mixed wastewater began to be degraded after day 1. Further research indicated that cehA gene was expressed after day 1. Subsequently, carbaryl hydrolase was synthesized under gene regulation. Analysis revealed that cehA and carbaryl hydrolase were adaptive gene expressions and enzymes. Carbaryl as stimulus signal started cehA gene expression through signal transduction pathway. This process took one day for R. sphaeroides. However, organics in 100, 500 mg/L COD groups were deficient, which could not maintain R. sphaeroides growth for over one day. Organics in SPW provided sufficient carbon sources for R. sphaeroides under other groups. The method could complete the mixed (SPW and carbaryl) wastewater treatment, carbaryl removal, the resource recycling of R. sphaeroides biomass as sludge simultaneously.

The removal of cyhalofop-butyl in soil by surplus Rhodopseudanonas palustris in wastewater purification

The biorestoration of cyhalofop-butyl and fertility in soil using Rhodopseudanonas palustris (R. palustris) in the treated wastewater were investigated in this research. Cyhalofop-butyl was not degraded under control group. The treated wastewater containing R. palustris degraded cyhalofop-butyl and remediated fertility. Interestingly, the cyhalofop-butyl-hydrolyzing carboxylesterase gene was expressed after inoculation 24 h. Subsequently, the cyhalofop-butyl-hydrolyzing carboxylesterase were synthesized to degrade cyhalofop-butyl. The cyhalofop-butyl started to be degraded after inoculation 24 h. The cyhalofop-butyl as stimulus signal induced cyhalofop-butyl-hydrolyzing carboxylesterase gene expression through signal transduction pathway. This process took 24 h for R. palustris as they were ancient bacteria. The residual organics in the wastewater provided sufficient carbon sources and energy for R. palustris under three dosage groups. The new method completed the remediation of cyhalofop-butyl pollution, the improvement of soil fertility and soybean processing wastewater treatment simultaneously, and realized the resource reutilization of wastewater and R. palustris as sludge.

The drivers of bacterial community underlying biogeographical pattern in Mollisol area of China

In order to better understand the composition and driving factors of the bacterial community in Mollisols, we selected 9 representative facility agricultural lands in Mollisol area of China for sampling, and described it on a larger spatial scale. Soil bacterial community structure in these 9 regions (determined by high-throughput sequencing analysis) showed significant differences at the genus level. The correlation between bacterial community composition and soil properties, contaminants and geographical latitude showed that the diversity of bacterial community was still strongly correlated with pH and SOM under the influence of phthalates (P < 0.05). Principal component Analysis (PCA) showed that soil properties (i.e. pH, organic matter, stacking density, the content of nitrogen, potassium, phosphorus) and PAEs level rather than geographic latitude were main drivers of differences in bacterial community structure. These factors account for 73.04% of the total variation of the bacterial community. Among them, PAEs act as a typical pollutant is the main factor driving the composition of bacterial community in facility agriculture Mollisols. This shows that PAEs is a potential pollution risk factor, which has important guiding significance for the sustainable and healthy development of agriculture in Mollisol area.