Effects of methanol on the performance of a novel BDE-47 degrading bacterial consortium QY2 in the co-metabolism process

Degradation and detoxification of 6PPD-quinone in water by ultraviolet-activated peroxymonosulfate: Mechanisms, byproducts, and impact on sediment microbial community

N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine quinone (6PPD-Q) has been identified to induce acute toxicity to multifarious aquatic organisms at exceptionally low concentrations. The ubiquity and harmful effects of 6PPD-Q emphasize the critical need for its degradation from water ecosystems. Herein, we explored the transformation of 6PPD-Q by an ultraviolet-activated peroxymonosulfate (UV/PMS) system, focusing on mechanism, products and toxicity variation. Results showed that complete degradation of 6PPD-Q was achieved when the initial ratio of PMS and 6PPD-Q was 60:1. The quenching experiments and EPR tests indicated that SO4•- and •OH radicals were primarily responsible for 6PPD-Q removal. Twenty-one degradation products were determined through high-resolution orbitrap mass spectrometry, and it was postulated that hydroxylation, oxidative cleavage, quinone decomposition, ring oxidation, as well as rearrangement and deamination were the major transformation pathways of 6PPD-Q. Toxicity prediction revealed that all identified products exhibited lower acute and chronic toxicities to fish, daphnid and green algae compared to 6PPD-Q. Exposure experiments also uncovered that 6PPD-Q considerably reduced the community diversity and altered the community assembly and functional traits of the sediment microbiome. However, we discovered that the toxicity of 6PPD-Q degradation solutions was effectively decreased, suggesting the superior detoxifying capability of the UV/PMS system for 6PPD-Q. These findings highlight the underlying detrimental impacts of 6PPD-Q on aquatic ecosystems and enrich our understanding of the photochemical oxidation behavior of 6PPD-Q.

Investigating the degradation potential of microbial consortia for perfluorooctane sulfonate through a functional "top-down" screening approach

Perfluorooctane sulfonate (PFOS) is a prominent perfluorinated compound commonly found in the environment, known to pose various risks to human health. However, the removal of PFOS presents significant challenges, primarily due to the limited discovery of bacteria capable of effectively degrading PFOS. Moreover, single degradation bacteria often encounter obstacles in individual cultivation and the breakdown of complex pollutants. In contrast, microbial consortia have shown promise in pollutant degradation. This study employed a continuous enrichment method, combined with multiple co-metabolic substrates, to investigate a microbial consortium with the potential for PFOS degradation. By employing this methodology, we effectively identified a microbial consortium that demonstrated the capacity to reduce PFOS when exposed to an optimal concentration of methanol. The consortium predominantly comprised of Hyphomicrobium species (46.7%) along with unclassified microorganisms (53.0%). Over a duration of 20 days, the PFOS concentration exhibited a notable decrease of 56.7% in comparison to the initial level, while considering the exclusion of adsorption effects. Furthermore, by comparing the predicted metabolic pathways of the microbial consortium with the genome of a known chloromethane-degrading bacterium, Hyphomicrobium sp. MC1, using the KEGG database, we observed distinct variations in the metabolic pathways, suggesting the potential role of the unclassified microorganisms. These findings underscore the potential effectiveness of a "top-down" functional microbial screening approach in the degradation of stubborn pollutants.

Integrated transcriptomics and metabolomics analyses reveal the aerobic biodegradation and molecular mechanisms of 2,3',4,4',5-pentachlorodiphenyl (PCB 118) in Methylorubrum sp. ZY-1

2,3',4,4',5-pentachlorodiphenyl (PCB 118), a highly representative PCB congener, has been frequently detected in various environments, garnering much attention across the scientific community. The degradation of highly chlorinated PCBs by aerobic microorganisms is challenging due to their hydrophobicity and persistence. Herein, the biodegradation and adaptation mechanisms of Methylorubrum sp. ZY-1 to PCB 118 were comprehensively investigated using an integrative approach that combined degradation performance, product identification, metabolomic and transcriptomic analyses. The results indicated that the highest degradation efficiency of 0.5 mg L-1 PCB 118 reached 75.66% after seven days of inoculation when the bacteria dosage was 1.0 g L-1 at pH 7.0. A total of eleven products were identified during the degradation process, including low chlorinated PCBs, hydroxylated PCBs, and ring-opening products, suggesting that strain ZY-1 degraded PCB 118 through dechlorination, hydroxylation, and ring-opening pathways. Metabolomic analysis demonstrated that the energy supply and redox metabolism of strain ZY-1 was disturbed with exposure to PCB 118. To counteract this environmental stress, strain ZY-1 adjusted both the fatty acid synthesis and purine metabolism. The analysis of transcriptomics disclosed that multiple intracellular and extracellular oxidoreductases (e.g., monooxygenase, alpha/beta hydrolase and cytochrome P450) participated in the degradation of PCB 118. Besides, active efflux of PCB 118 and its degradation intermediates mediated by multiple transporters (e.g., MFS transporter and ABC transporter ATP-binding protein) might enhance bacterial resistance against these substances. These discoveries provided the inaugural insights into the biotransformation of strain ZY-1 to PCB 118 stress, illustrating its potential in the remediation of contaminated environments.

Unveiling the PCB biodegradation potential and stress survival strategies of resuscitated strain Pseudomonas sp. HR1

The exploration of resuscitated strains, facilitated by the resuscitation promoting factor (Rpf), has substantially expanded the pool of cultivated degraders, enhancing the screening of bio-inoculants for bioremediation applications. However, it remains unknown whether these resuscitated strains can re-enter the viable but non-culturable (VBNC) state and the specific stress conditions that trigger such a transition. In this work, the whole genome, and polychlorinated biphenyl (PCB)-degrading capabilities of a resuscitated strain HR1, were investigated. Notably, the focus of this exploration was on elucidating whether HR1 would undergo a transition into the VBNC state when exposed to low temperature and PCBs, with and without the presence of heavy metals (HMs). The results suggested that the resuscitated strain Pseudomonas sp. HR1 harbored various functional genes related to xenobiotic biodegradation, demonstrating remarkable efficiency in Aroclor 1242 degradation and strong resistance against stress induced by low temperature and PCBs. Nevertheless, when exposed to the combined stress of low temperature, PCBs, and HMs, HR1 underwent a transition into the VBNC state. This transition was characterized by significant decreases in enzyme activities and notable changes in both morphological and physiological traits when compared to normal cells. Gene expression analysis revealed molecular shifts underlying the VBNC state, with down-regulated genes showed differential expression across multiple pathways and functions, including oxidative phosphorylation, glycolysis, tricarboxylic acid cycle, amino acid metabolism, translation and cytoplasm, while up-regulated genes predominantly associated with transcription regulation, membrane function, quorum sensing, and transporter activity. These findings highlighted the great potential of resuscitated strains as bio-inoculants in bioaugmentation and shed light on the survival mechanisms of functional strains under stressful conditions, which should be carefully considered during bioremediation processes.

Biodegradation of chloroxylenol by an aerobic enrichment consortium and a newly identified Rhodococcus strain

Chloroxylenol is a commonly used antimicrobial agent in antibacterial and disinfection products, which has been detected in various environments, such as wastewater treatment plants, rivers, seawater, and even drinking water, with concentrations ranging from ng/L to mg/L. However, the biodegradation of chloroxylenol received limited attention with only sporadic reports available so far. In this study, an efficient chloroxylenol-degrading consortium, which could degrade 20 mg/L chloroxylenol within two days, was obtained after five months of enrichment. Amplicon sequencing analysis revealed a decrease in the α-diversity (e.g., Shannon index and Inv_Simpson index) of the community during the domestication process. Microbial community dynamics were uncovered, with sequences affiliated to Achromobacter, Pseudomonas, and Rhodococcus identified as the most abundant taxonomic groups. From the consortium, five pure isolates were obtained; however, it was found that only one strain of Rhodococcus could degrade chloroxylenol. Strain Rhodococcus sp. DMU2021 could degrade chloroxylenol efficiently under the conditions of temperature 30-40 °C, and neutral/alkaline conditions. Chloroxylenol was toxic to strain DMU2021 and triggered both enzymatic and non-enzymatic antioxidant systems in response. This study provides novel insights into the biodegradation process of chloroxylenol, as well as valuable bioresources for bioremediation.

Degradation of Benzo[a]pyrene and 2,2',4,4'-Tebrabrominated Diphenyl Ether in Cultures Originated from an Agricultural Soil

Benzo[a]pyrene (BaP) and 2,2',4,4'-tetrabrominated diphenyl ether (BDE-47) are common contaminants in the environment, posing a threat to the ecosystems and human health. Currently, information on the microbial metabolism of BaP and BDE-47 as well as the correlated bacteria is still limited. This research aimed to study the degradation of BaP and BDE-47 by enriched cultures originated from an agricultural soil in Tianjin (North China) and characterize the bacteria involved in the degradation. Two sets of experiments were set up with BaP and BDE-47 (2 mg/L) as the sole carbon source, respectively. The degradation of BaP and BDE-47 occurred at rate constants of 0.030 /d and 0.026 /d, respectively. For BaP, the degradation products included benzo[a]pyrene-9,10-dihydrodiol or its isomers, ben-zo(a)pyrene-7,8-dihydrodiol-9,10-epoxide, and cis-4 (8-hydroxypyrenyl-7)-2-oxo-3-butenoic acid. For BDE-47, the degradation products included 2,2',4-tribrominated diphenyl ether (BDE-17), 2,4-dibrominated diphenyl ether (BDE-7), and hydroxylated dibromodiphenyl ether. The bacterial community structures in the original soil, the BaP culture, and the BDE-47 culture were quite different. The richness and diversity of bacteria in the two cultures were much lower than that in the original soil, and the BaP culture had higher richness and diversity than the BDE-47 culture. In the BaP culture, multiple species such as Niabella (23.4%), Burkholderia-Caballeronia-Paraburkholderia (13.7%), Cupriavidus (8.3%), and Allorhizobi-um-Neorhizobium-Pararhizobium-Rhizobium (8.0%) were dominant. In the BDE-47 culture, an unassigned species in the Rhizobiaceae was dominant (82.3%). The results from this study provide a scientific basis for the risk assessment and bioremediation of BaP and/or BDE-47 in a contaminated environment.

Unraveling the functional instability of bacterial consortia in crude oil degradation via integrated co-occurrence networks

Introduction

Soil ecosystems are threatened by crude oil contamination, requiring effective microbial remediation. However, our understanding of the key microbial taxa within the community, their interactions impacting crude oil degradation, and the stability of microbial functionality in oil degradation remain limited.

Methods

To better understand these key points, we enriched a crude oil-degrading bacterial consortium generation 1 (G1) from contaminated soil and conducted three successive transfer passages (G2, G3, and G4). Integrated Co-occurrence Networks method was used to analyze microbial species correlation with crude oil components across G1-G4.

Results and discussion

In this study, G1 achieved a total petroleum hydrocarbon (TPH) degradation rate of 32.29% within 10 days. Through three successive transfer passages, G2-G4 consortia were established, resulting in a gradual decrease in TPH degradation to 23.14% at the same time. Specifically, saturated hydrocarbon degradation rates ranged from 18.32% to 14.17% among G1-G4, and only G1 exhibited significant aromatic hydrocarbon degradation (15.59%). Functional annotation based on PICRUSt2 and FAPROTAX showed that functional potential of hydrocarbons degradation diminished across generations. These results demonstrated the functional instability of the bacterial consortium in crude oil degradation. The relative abundance of the Dietzia genus showed the highest positive correlation with the degradation efficiency of TPH and saturated hydrocarbons (19.48, 18.38, p < 0.05, respectively), Bacillus genus demonstrated the highest positive correlation (21.94, p < 0.05) with the efficiency of aromatic hydrocarbon degradation. The key scores of Dietzia genus decreased in successive generations. A significant positive correlation (16.56, p < 0.05) was observed between the Bacillus and Mycetocola genera exclusively in the G1 generation. The decline in crude oil degradation function during transfers was closely related to changes in the relative abundance of key genera such as Dietzia and Bacillus as well as their interactions with other genera including Mycetocola genus. Our study identified key bacterial genera involved in crude oil remediation microbiome construction, providing a theoretical basis for the next step in the construction of the oil pollution remediation microbiome.

Advanced electrocatalytic redox processes for environmental remediation of halogenated organic water pollutants

Halogenated organic compounds are widespread, and decades of heavy use have resulted in global bioaccumulation and contamination of the environment, including water sources. Here, we introduce the most common halogenated organic water pollutants, their classification by type of halogen (fluorine, chlorine, or bromine), important policies and regulations, main applications, and environmental and human health risks. Remediation techniques are outlined with particular emphasis on carbon-halogen bond strengths. Aqueous advanced redox processes are discussed, highlighting mechanistic details, including electrochemical oxidations and reductions of the water-oxygen system, and thermodynamic potentials, protonation states, and lifetimes of radicals and reactive oxygen species in aqueous electrolytes at different pH conditions. The state of the art of aqueous advanced redox processes for brominated, chlorinated, and fluorinated organic compounds is presented, along with reported mechanisms for aqueous destruction of select PFAS (per- and polyfluoroalkyl substances). Future research directions for aqueous electrocatalytic destruction of organohalogens are identified, emphasizing the crucial need for developing a quantitative mechanistic understanding of degradation pathways, the improvement of analytical detection methods for organohalogens and transient species during advanced redox processes, and the development of new catalysts and processes that are globally scalable.

Alkaline-thermal hydrolysate of waste activated sludge as a co-metabolic substrate enhances biodegradation of refractory dye reactive black 5

Aromatic azo dyes possess inherent resistance and are known to be carcinogenic, posing a significant threat to human and ecosystems. Enhancing the biodegradation of azo dyes usually requires the presence of co-metabolic substrates to optimize the process. In addressing the issue of excessive waste activated sludge (WAS) generation, this study explored the potential of utilizing alkaline-thermal hydrolysate of WAS as a co-metabolic substrate to boost the degradation of reactive black 5 (RB5) dyes. The acclimated microbial consortium, when supplemented with the WAS hydrolysate obtained at a hydrolysis temperature of 30 °C, achieved an impressive RB5 decolorization efficiency of 90.3% (pH = 7, 35 °C) with a corresponding COD removal efficiency of 45.0%. The addition of WAS hydrolysate as a co-substrate conferred the consortium with a remarkable tolerance to high dye concentration (1500 mg/L RB5) and salinity levels (4-5%), surpassing the performance of conventional co-metabolic sugars in RB5 degradation. 3D-EEM analysis revealed that protein-like substances rich in tyrosine and tryptophan, present in the WAS hydrolysate, played a crucial role in promoting RB5 biodegradation. Furthermore, the microbial consortium community exhibited an enrichment of dye-degrading species, including Acidovorax, Bordetella, Kerstersia, and Brevundimonas, which dominated the community. Notably, functional genes associated with dye degradation and intermediates were also enriched during the RB5 decolorization and biodegradation process. These findings present a practical strategy for the simultaneous treatment of dye-containing wastewater and recycling of WAS.

Methanol promotes the biodegradation of 2,2',3,4,4',5,5'-heptachlorobiphenyl (PCB 180) by the microbial consortium QY2: Metabolic pathways, toxicity evaluation and community response

As one of the most frequently detected PCB congeners in human adipose tissue, 2,2',3,4,4',5,5'-heptachlorobiphenyl (PCB 180) has attracted much attention. However, PCB 180 is difficult to be directly utilized by microorganisms due to its hydrophobicity and obstinacy. Herein, methanol (5 mM) as a co-metabolic carbon source significantly stimulated the degradation performance of microbial consortium QY2 for PCB 180 (51.9% higher than that without methanol addition). Six metabolic products including low-chlorinated PCBs and chlorobenzoic acid were identified during co-metabolic degradation, denoting that PCB 180 was metabolized via dechlorination, hydroxylation and ring-opening pathways. The oxidative stress and apoptosis induced by PCB 180 were dose-dependent, but the addition of methanol effectively promoted the tolerance of consortium QY2 to resist unfavorable environmental stress. Additionally, the significant reduction of intracellular reactive oxygen species (ROS) and enhancement of cell viability during methanol co-metabolic degradation proved that the degradation was a detoxification process. The microbial community and network analyses suggested that the potential PCB 180 degrading bacteria in the community (e.g., Achromobacter, Cupriavidus, Methylobacterium and Sphingomonas) and functional abundance of metabolic pathways were selectively enriched by methanol, and the synergies among species whose richness increased after methanol addition might dominate the degradation process. These findings provide new insights into the biodegradation of PCB 180 by microbial consortium.

Simultaneous adsorption and biodegradation of polychlorinated biphenyls using resuscitated strain Streptococcus sp. SPC0 immobilized in polyvinyl alcohol‑sodium alginate

Enhanced bioremediation of polychlorinated biphenyls (PCBs) is a promising and effective strategy for eliminating the risks posed by PCBs. In the present study, the feasibility of utilizing an immobilization approach to enhance the PCBs degradation performance of a resuscitated strain Streptococcus sp. SPC0 was evaluated. The results indicated that a mixed matrix containing polyvinyl alcohol (PVA) and sodium alginate (SA) used as immobilized carriers provided a porous microstructure space for SPC0 colonization and proliferation. The enhanced removal of PCBs by immobilized SPC0 was attributed to simultaneous adsorption and biodegradation performances of PVA-SA-SPC0 beads. The relative equilibrium adsorption capacity of immobilized beads increased with elevated initial concentration, and the maximum theoretical value calculated was 1.64 mg/g. The adsorption process of PCBs by immobilized beads was well fitted to the quasi-second-order kinetic model, and most suitable for Langmuir isotherm model. Immobilized SPC0 enhanced PCB removal with 1.0-7.1 times higher than free cells. Especially, more effective removal of PCBs at higher concentrations could be achieved, in which 73.9 % of 20 mg/L PCBs was removed at 12 h by immobilized SPC0, whereas only 12.0 % by free cells. Moreover, the immobilized SPC0 with excellent stability and reusability retained almost 100 % of the original PCBs removal activity after reusing four times. These results revealed the application potential of immobilizing resuscitated strains for enhanced bioremediation of PCBs.

Enhanced biodegradation of thiamethoxam with a novel polyvinyl alcohol (PVA)/sodium alginate (SA)/biochar immobilized Chryseobacterium sp H5

Long-term and extensive usage of thiamethoxam, the second-generation neonicotinoid insecticide, has caused a serious threat to non-target organisms and ecological security. Efficient immobilized microorganism techniques are a sustainable solution for bioremediation of thiamethoxam contamination. A Gram-negative aerobic bacterium Chryseobacterium sp H5 with high thiamethoxam-degrading efficiencies was isolated from activated sludge. Then we developed a novel polyvinyl alcohol (PVA)/sodium alginate (SA)/biochar bead with this functional microbe immobilization to enhance the biodegradation and removal of thiamethoxam. Results indicated that the total removal and biodegradation rate of thiamethoxam with PVA/SA/biochar (0.7 %) beads with Chryseobacterium sp H5 immobilization at 30 °C and pH of 7.0 within 7 d reached about 90.47 % and 68.03 %, respectively, much higher than that using PVA/SA immobilized microbes (75.06 %, 56.05 %) and free microbes (61.72 %). Moreover, the PVA/SA/biochar (0.7 %) immobilized microbes showed increased tolerance to extreme conditions. Biodegradation metabolites of thiamethoxam were identified and two intermediates were first reported. Based on the identified biodegradation intermediates, cleavage of C-N between the 2-chlorothiazole ring and oxadiazine, dichlorination, nitrate reduction and condensation reaction would be the major biodegradation routes of thiamethoxam. Results of this work suggested the novel PVA/SA/biochar beads with Chryseobacterium sp H5 immobilization would be helpful for the effective bioremediation of thiamethoxam contamination.

Effect of the degradation performance on carbon tetrachloride by anaerobic co-metabolism under different external energy sources

In this research, a comprehensive study was carried out on the removal of carbon tetrachloride (CT) in the anaerobic co-metabolism (ACM) reactor. The experiments showed that when the hydraulic retention time (HRT) was 36 h, pH was 7, and influent CT was 2.5mg/L, the average removal efficiency reached 82.45 ± 2.56% in the glucose co-metabolism substrate reactor, exhibiting a dramatic excellent difference in reaction performance from the other two reactors (p < 0.05) and a favorable tolerance on the CT shock loading. The content of extracellular polymeric substances (EPS) and volatile fatty acids (VFA) demonstrated that glucose could supply more energy to protect the microorganisms, which was the appropriate external energy source. Moreover, microbial community structure and biostatistics analysis demonstrated that Pseudomonas was the most important dechlorination bacteria in ACM reactors, which might via dehalogenation process mediate the transformation of CT. The succession of methanogenic bacteria further demonstrated that CT degradation using co-digestion require to destroy hydrogenotrophic methane generation pathway and the external energy substances could make up the lack of hydrogen in the treatment of CT. The change of intermediate products hinted that anaerobic dechlorination process of CT in an ACM reactor was a sequential dechlorination process, and major transformation products measured were CF. Overall, this study has improved our understanding of the roles of CT degradation process in ACM reactors.

Functional bacterial consortium responses to biochar and implications for BDE-47 transformation: Performance, metabolism, community assembly and microbial interaction

The influence of biochar on the biodegradation of persistent organic pollutants (POPs) has been extensively studied. However, the underlying mechanisms behind the response of functional microbial consortia to biochar remain poorly understood. Herein, we systematically explored the effect of biochar on 2,2',4,4'-tetrabrominated ether (BDE-47) biodegradation, and investigated the interaction and assembly mechanism of the functional bacterial consortium QY2. The results revealed that the biodegradation efficiency of QY2 for BDE-47 increased from 53.85% to 94.11% after the addition of biochar. Fluorescence excitation-emission matrix and electrochemical analysis showed that biochar-attached biofilms were rich in redox-active extracellular polymeric substances (EPS, 3.03-fold higher than free cell), whose strong interaction with biochar facilitated the electron transfer of the biofilm, thus enhancing the debromination degradation of BDE-47. Meanwhile, the assembly model and molecular ecological networks analysis indicated that bacterial community assembly in biofilms was more driven by deterministic processes (environmental selection >75.00%) upon biochar stimulation and exhibited closer interspecific cooperative interactions, leading to higher biodiversity and broader habitat niche breadth for QY2 in response to BDE-47 disturbance. Potential degraders (Methylobacterium, Sphingomonas, Microbacterium) and electrochemical bacteria (Ochrobactrum) were selectively enriched, whose role as keystone bacteria may be participated in biofilm formation and redox-active EPS secretion (r > 0.5, P < 0.05). These findings deepen the understanding of the mechanisms by which biochar promotes microbial degradation of PBDEs and provided a theoretical basis for better regulation of functional bacterial communities during environmental remediation.

The potential role of betaine in enhancement of microbial-assisted phytoremediation of benzophenone-3 contaminated soil

Benzophenone-3 (BP-3) is an emerging environmental pollutant used in personal care products, helping to reduce the risk of ultraviolet radiation to human skin. The BP-3 removal potential from soil by tobacco (Nicotiana tabacum) assisted with Methylophilus sp. FP-6 was explored in our previous study. However, the reduced BP-3 remediation efficiency by FP-6 in soil and the inhibited plant growth by BP-3 limited the application of this phytoremediation strategy. The aim of the present study was to reveal the potential roles of betaine, as the methyl donor of methylotrophic bacteria and plant regulator, in improving the strain FP-6-assisted phytoremediation capacity of BP-3 contaminated soil. The results revealed that strain FP-6 could use betaine as a co-metabolism substrate to enhance the BP-3 degradation activity. About 97.32% BP-3 in soil was effectively removed in the phytoremediation system using tobacco in combination with FP-6 and betaine for 40 d while the concentration of BP-3 in tobacco significantly reduced. Moreover, the biomass and photosynthetic efficiency of plants were remarkably improved through the combined treatment of betaine and strain FP-6. Simultaneously, inoculation of FP-6 in the presence of betaine stimulated the change of local microbial community structure, which might correlate with the production of a series of hydrolases and reductases involved in soil carbon, nitrogen and phosphorus cycling processes. Meantime, some of the dominant bacteria could secrete various multiple enzymes involved in degrading organic pollutants, such as laccase, to accelerate the demethylation and hydroxylation of BP-3. Overall, the results from this study proposed that the co-metabolic role of betaine could be utilized to strengthen microbial-assisted phytoremediation process by increasing the degradation ability of methylotrophic bacteria and enhancing plant tolerance to BP-3. The present results provide novel insights and perspectives for broadening the engineering application scope of microbial-assisted phytoremediation of organic pollutants without sacrificing economic crop safety.

Cometabolic biodegradation system employed subculturing photosynthetic bacteria: A new degradation pathway of 4-chlorophenol in hypersaline wastewater

4-chlorophenol (4-CP) as a toxic persistent pollutant is quite difficult treatment by using traditional biological processes. Herein, photosynthetic bacteria (PSB) driven cometabolic biodegradation system associated with exogeneous carbon sources (e.g., sodium acetate) has been demonstrated as an effective microbial technique. The biodegradation rate (r_i) can be at 0.041 d^-1 with degradation efficiency of 93% in 3094 lx. Through the study of subculturing PSB in absence of NaCl, it was found that 50% inoculation time can be saved but keeping a similar 4-CP biodegradation efficiency in scale-up salinity system. A new plausible biodegradation pathway for 4-CP in 4th G PSB cometabolic system is proposed based on the detected cyclohexanone generation followed by ring opening. It is probably ascribed to the increasement of Firmicutes and Bacteroidetes at phyla level classified based on microbial community. This study contributes to a new insight into cometabolic technology for chlorophenol treatment in industrial hypersaline wastewater.

Understanding the role of biochar in affecting BDE-47 biodegradation by Pseudomonas plecoglossicida: An integrated analysis using chemical, biological, and metabolomic approaches

Biochar-assisted microbial degradation technology is considered as an important strategy to eliminate organic pollutants, but the mechanism of biochar in affecting biodegradation has not been systematically studied. To address this knowledge gap, the effect of various biochars on biodegradation of different initial concentrations of BDE-47 by Pseudomonas plecoglossicida was investigated. The results showed that biochar exhibited significant promotion to the biodegradation of BDE-47, especially at concentrations of BDE-47 above 100 μg/L. The promotion effect was negatively influenced by the aromaticity and micropore volume of biochar. Biochar alleviated the cytotoxicity of BDE-47 to P. plecoglossicida and promoted cell proliferation based on toxicity assays. Additionally, biochar acted as shelter and stimulated the secretion of extracellular polymeric substances, which might support P. plecoglossicida to struggle with extreme conditions. Metabolomic analysis indicated that biochar resulted in upregulation expression of 38 metabolites in P. plecoglossicida. These upregulated metabolites were mainly related to glyoxylate and dicarboxylate metabolism, citrate cycle, and serial amino acid metabolism, suggesting that biochar could improve the BDE-47 biodegradation via enhancing oxidative metabolism and energy supply of the bacterial cells. This work elucidates how biochar can affect BDE-47 biodegradation and provides insights for the application prospect of biochar-assisted microbial degradation technology in the environment.

Biodegradation of tricresyl phosphates isomers by a novel microbial consortium and the toxicity evaluation of its major products

A novel microbial consortium ZY1 capable of degrading tricresyl phosphates (TCPs) was isolated, it could quickly degrade 100% of 1 mg/L tri-o-cresyl phosphate (ToCP), tri-p-cresyl phosphate (TpCP) and tri-m-cresyl phosphate (TmCP) within 36, 24 and 12 h separately and intracellular enzymes occupied the dominated role in TCPs biodegradation. Additionally, triphenyl phosphate (TPHP), 2-ethylhexyl diphenyl phosphate (EHDPP), bisphenol-A bis (diphenyl phosphate) (BDP), tris (2-chloroethyl) phosphate (TCEP) and tris (1-chloro-2-propyl) phosphate (TCPP) could also be degraded by ZY1 and the aryl-phosphates was easier to be degraded. The TCPs reduction observed in freshwater and seawater indicated that high salinity might weak the degradability of ZY1. The detected degradation products suggested that TCPs was mainly metabolized though the hydrolysis and hydroxylation. Sequencing analysis presented that the degradation of TCPs relied on the cooperation between sphingobacterium, variovorax and flavobacterium. The cytochrome P450/NADPH-cytochrome P450 reductase and phosphatase were speculated might involve in TCPs degradation. Finally, toxicity evaluation study found that the toxicity of the diesters products was lower than their parent compound based on the generation of the intracellular reactive oxygen (ROS) and the apoptosis rate of A549 cell. Taken together, this research provided a new insight for the bioremediation of TCPs in actual environment.

Aerobic and anaerobic biodegradation of BDE-47 by bacteria isolated from an e-waste-contaminated site and the effect of various additives

Degradation experiments are conducted to specifically compare the degradation of 2,2',4,4'-tetrabromodiphenyl ether (BDE-47) by aerobic and anaerobic strains isolated from real e-waste sites contaminated by BDE-47. The effect of carbon sources, inducers and surfactants on the degradation was examined to strengthen such a comparison. An aerobic strain, B. cereus S1, and an anaerobic strain, A. faecalis S4, were obtained. The results indicated that BDE-47 could be used as the sole carbon source by B. cereus S1 and A. faecalis S4 under aerobic and anaerobic conditions, respectively. The degradation of BDE-47 by B. cereus S1 and A. faecalis S4 was illustrated a first-order kinetics process obtaining a removal efficiency of 61.6% and 51.6% with a first-order rate constant of 0.0728 d^-1 and 0.0514 d^-1, and corresponding half-life of 8.7 d and 13.5 d, respectively. The addition of carbon sources (yeast extract, glucose, acetic acid and ethanol) and inducers (2,4-dichlorophenol, bisphenol A and toluene) promoted BDE-47 degradation by both B. cereus S1 and A. faecalis S4 under aerobic and anaerobic conditions, while hydroquinone as the inducer inhibited the degradation. All of the surfactants tested (CTAB, Tween 80, Triton X-100, rhamnolipid and SDS) showed inhibitory effect. BDE-47 degradation by B. cereus S1 under aerobic condition was more efficient than A. faecalis S4 under anaerobic condition whether with or without the additives. The results of the study indicated that in the field sites contaminated by BDE-47, the aerobic condition can be more favorable for BDE-47 removal and the degradation can be further enhanced by applying suitable carbon sources and inducers.

Enhanced bioremediation of 2,3',4,4',5-pentachlorodiphenyl by consortium GYB1 immobilized on sodium alginate-biochar

2,3',4,4',5-pentachlorodiphenyl (PCB 118), a dioxin-like PCB, is often detected in the environment and is difficult to be aerobically biodegraded. In this study, a novel polychlorinated biphenyl degrading consortium GYB1 that can metabolize PCB 118 was successfully obtained by acclimatization process. To enhance the application performance of free bacterial cells, consortium GYB1 was immobilized with sodium alginate and biochar to prepare SC-GYB1 beads. Orthogonal experiments indicated that the optimal composition of the beads (0.2 g) was 2.0% sodium alginate (SA) content, 2.0% wet weight of cells and 1.5% biochar content, which can degrade 50.50% PCB 118 in 5 d. Immobilization shortened the degradation half-life of 1 mg/L PCB 118 by consortium GYB1 from 8.14 d to 3.79 d and made the beads more robust to respond to environmental stress. The SC-GYB1 beads could even keep considerable PCB degradation ability under 200 mg/L Cd²⁺ stress. According to 16S rRNA gene analysis, Pseudomonas and Stenotrophomonas played the dominant role in consortium GYB1. And embedding obviously altered the community structure and the key bacterial genera during the PCB removal process. Therefore, the immobilization of bacteria consortium by sodium alginate-biochar enhanced the biodegradation of PCB 118, which will provide new insights into functional microorganisms' actual application for PCB restoration.