Ecotoxicity of phenol and cresols to aquatic organisms: A review

Unlocking the genomic potential of Red Sea coral probiotics

The application of beneficial microorganisms for corals (BMC) decreases the bleaching susceptibility and mortality rate of corals. BMC selection is typically performed via molecular and biochemical assays, followed by genomic screening for BMC traits. Herein, we present a comprehensive in silico framework to explore a set of six putative BMC strains. We extracted high-quality DNA from coral samples collected from the Red Sea and performed PacBio sequencing. We identified BMC traits and mechanisms associated with each strain as well as proposed new traits and mechanisms, such as chemotaxis and the presence of phages and bioactive secondary metabolites. The presence of prophages in two of the six studied BMC strains suggests their possible distribution within beneficial bacteria. We also detected various secondary metabolites, such as terpenes, ectoines, lanthipeptides, and lasso peptides. These metabolites possess antimicrobial, antifungal, antiviral, anti-inflammatory, and antioxidant activities and play key roles in coral health by reducing the effects of heat stress, high salinity, reactive oxygen species, and radiation. Corals are currently facing unprecedented challenges, and our revised framework can help select more efficient BMC for use in studies on coral microbiome rehabilitation, coral resilience, and coral restoration.

Taxonomic identification, phenol biodegradation and soil remediation of the strain Rhodococcus sacchari sp. nov. Z13T

Phenols are highly toxic chemicals that are extensively used in industry and produce large amounts of emissions. Notably, phenols released into the soil are highly persistent, causing long-term harm to human health and the environment. In this study, a gram-positive, aerobic, and rod-shaped bacterial strain, Z13T, with efficient phenol degradation ability, was isolated from the soil of sugarcane fields. Based on the physiological properties and genomic features, strain Z13T is considered as a novel species of the genus Rhodococcus, for which the name Rhodococcus sacchari sp. nov. is proposed. The type strain is Z13T (= CCTCC AB 2022327T = JCM 35797T). This strain can use phenol as its sole carbon source. Z13T was able to completely degrade 1200 mg/L phenol within 20 h; the maximum specific growth rate was μmax = 0.93174 h-1, and the maximum specific degradation rate was qmax = 0.47405 h-1. Based on whole-genome sequencing and Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis, strain Z13T contains a series of phenol degradation genes, including dmpP, CatA, dmpB, pcaG, and pcaH, and can metabolize aromatic compounds. Moreover, the potential of strain Z13T for soil remediation was investigated by introducing Z13T into simulated phenol-contaminated soil, and the soil microbial diversity was analyzed. The results showed that 100% of the phenol in the soil was removed within 7.5 d. Furthermore, microbial diversity analysis revealed an increase in the relative species richness of Oceanobacillus, Chungangia, and Bacillus.

Electroanalytical analysis of phenol oxidation using bacteria immobilized by a polycaprolactone coating on the copper electrode surface

The copper electrode modified by bacteria immobilised by a polycaprolactone film was successfully developed by electropolymerisation for the purpose of determining the presence of phenol. Electrochemical techniques such as square-wave voltammetry (SWV), cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) were used to characterize the electrochemical properties of the Cu-polymer/bacteria electrode. The results show that the intensity of the phenol oxidation peak increases with concentration, allowing us to obtain good analytical results with DL of 2.156 × 10-7 M and QL which is 7.2 × 10-7 M , confirming that the biosensor has excellent electroanalytical activity for phenol oxidation, with good stability and a wide linear range. Our electrode is based on a easily available and inexpensive material, as well as on its simple preparation, which has demonstrated high performance for phenol.

Biodegradation of phenolic pollutants and bioaugmentation strategies: A review of current knowledge and future perspectives

The widespread use of phenolic compounds renders their occurrence in various environmental matrices, posing ecological risks especially the endocrine disruption effects. Biodegradation-based techniques are efficient and cost-effective in degrading phenolic pollutants with less production of secondary pollution. This review focuses on phenol, 4-nonylphenol, 4-nitrophenol, bisphenol A and tetrabromobisphenol A as the representatives, and summarizes the current knowledge and future perspectives of their biodegradation and the enhancement strategy of bioaugmentation. Biodegradation and isolation of degrading microorganisms were mainly investigated under oxic conditions, where phenolic pollutants are typically hydroxylated to 4-hydroxybenzoate or hydroquinone prior to ring opening. Bioaugmentation efficiencies of phenolic pollutants significantly vary under different application conditions (e.g., increased degradation by 10-95% in soil and sediment). To optimize degradation of phenolic pollutants in different matrices, the factors that influence biodegradation capacity of microorganisms and performance of bioaugmentation are discussed. The use of immobilization strategy, indigenous degrading bacteria, and highly competent exogenous bacteria are proposed to facilitate the bioaugmentation process. Further studies are suggested to illustrate 1) biodegradation of phenolic pollutants under anoxic conditions, 2) application of microbial consortia with synergistic effects for phenolic pollutant degradation, and 3) assessment on the uncertain ecological risks associated with bioaugmentation, resulting from changes in degradation pathway of phenolic pollutants and alterations in structure and function of indigenous microbial community.

Widespread and active piezotolerant microorganisms mediate phenolic compound degradation under high hydrostatic pressure in hadal trenches

Phenolic compounds, as well as other aromatic compounds, have been reported to be abundant in hadal trenches. Although high-throughput sequencing studies have hinted at the potential of hadal microbes to degrade these compounds, direct microbiological, genetic and biochemical evidence under in situ pressures remain absent. Here, a microbial consortium and a pure culture of Pseudomonas, newly isolated from Mariana Trench sediments, efficiently degraded phenol under pressures up to 70 and 60 MPa, respectively, with concomitant increase in biomass. By analyzing a high-pressure (70 MPa) culture metatranscriptome, not only was the entire range of metabolic processes under high pressure generated, but also genes encoding complete phenol degradation via ortho- and meta-cleavage pathways were revealed. The isolate of Pseudomonas also contained genes encoding the complete degradation pathway. Six transcribed genes (dmpKLMNOPsed) were functionally identified to encode a multicomponent hydroxylase catalyzing the hydroxylation of phenol and its methylated derivatives by heterogeneous expression. In addition, key catabolic genes identified in the metatranscriptome of the high-pressure cultures and genomes of bacterial isolates were found to be all widely distributed in 22 published hadal microbial metagenomes. At microbiological, genetic, bioinformatics, and biochemical levels, this study found that microorganisms widely found in hadal trenches were able to effectively drive phenolic compound degradation under high hydrostatic pressures. This information will bridge a knowledge gap concerning the microbial aromatics degradation within hadal trenches.

Supplementary Information

The online version contains supplementary material available at 10.1007/s42995-024-00224-2.

An Overview of Recycling Phenolic Resin

Over a century ago, phenolic formaldehyde (PF) resin was developed and continues to increase in yield due to its diverse applications. However, PF resin is a thermosetting plastic lacking fluidity and moldability, which are nondegradable in natural environments, leading to severe threats to fossil resources as well as global environmental crises. As a result, recycling PF resin is extremely important. In this review, we provide the recent advances in the recycling of PF resin, which includes mechanical recycling, chemical recycling, and utilization of carbon-based materials. The advantages and disadvantages of each strategy are evaluated from a green chemistry perspective. This article aims to attract interest in PF resin design, synthesizing, application and recycling, offering useful suggestions.

Biotoxicity dynamic change and key toxic organics identification of coal chemical wastewater along a novel full-scale treatment process

It is particularly important to comprehensively assess the biotoxicity variation of industrial wastewater along the treatment process for ensuring the water environment security. However, intensive studies on the biotoxicity reduction of industrial wastewater are still limited. In this study, the toxic organics removal and biotoxicity reduction of coal chemical wastewater (CCW) along a novel full-scale treatment process based on the pretreatment process-anaerobic process-biological enhanced (BE) process-anoxic/oxic (A/O) process-advanced treatment process was evaluated. This process performed great removal efficiency of COD, total phenol, NH4+-N and total nitrogen. And the biotoxicity variation along the treatment units was analyzed from the perspective of acute biotoxicity, genotixicity and oxidative damage. The results indicated that the effluent of pretreatment process presented relatively high acute biotoxicity to Tetrahymena thermophila. But the acute biotoxicity was significantly reduced in BE-A/O process. And the genotoxicity and oxidative damage to Tetrahymena thermophila were significantly decreased after advanced treatment. The polar organics in CCW were identified as the main biotoxicity contributors. Phenols were positively correlated with acute biotoxicity, while the nitrogenous heterocyclic compounds and polycyclic aromatic hydrocarbons were positively correlated with genotoxicity. Although the biotoxicity was effectively reduced in the novel full-scale treatment process, the effluent still performed potential biotoxicity, which need to be further explored in order to reduce environmental risk.

Ultrasound and defect engineering-enhanced nanozyme with high laccase-like activity for oxidation and detection of phenolic compounds and adrenaline

Perusing metal-based redox nanozyme offers new opportunity for pollutant removal and biosensor, but ultrasound (US)-driven laccase-like nanozyme remains a significant challenge, especially in combination with defect engineering strategy. Herein, the Cu2Ov@Ce-TCPP was synthesized by doping Ce3+ on the surface of Cu2O nanocube and then coating with the porphyrin sonosensitizer. The Ce-doped porphyrin metal-structure in nanozyme was demonstrated to generate oxygen vacancy defects, which could obviously promote the laccase-like activity of Cu2Ov@Ce-TCPP nanozyme under US. XPS characterization and density functional theory (DFT) theoretical calculation revealed that the ultrasonic stimulation is beneficial to accelerate the electron transfer rate and O2 adsorption to improve catalytic activity, and Cu2Ov@Ce-TCPP nanozyme exhibits low adsorption energy and activation energy due to the presence of oxygen defect site, resulting in high laccase-like activity. The interaction between Ce atom and porphyrin structure also improved the sonocatalytic ability of the nanozyme. Meanwhile, Cu2Ov@Ce-TCPP nanozyme has been used for detecting and degrading a series of phenolic compounds. The detection adrenaline method has a linear range of 3.3-1000 μM and a detection limit as low as 0.96 μM with good reproducibility. The developed US-enhancing and recyclable laccase-like nanozyme system provides a promising strategy for the oxidation and detection of phenolic compounds.

Emergency response to ecological protection in maritime phenol spills: Emergency monitor, ecological risk assessment, and reduction

Recently, hundreds of maritime accidental spills of hazardous chemicals have raised public concerns, especially for phenol due to its potential of spills and highly toxicity. Therefore, for marine ecological protection, this article prepared specific strategies of emergency response to phenol spills. Through the identification for phenol behavior at sea, migration prediction, emergency monitor, as well as their new methods were reviewed. Further, ecological risk assessment and seawater quality criteria were conducted by using a species sensitivity distribution (SSD) approach, wherein, risk quotient (RQ) indicated phenol of simulated marine spills posed a high risk (RQ > 1) in 30 days. The method with eco-friendliness and high-efficiency for phenol reduction was constructed by combination of dredging equipment such as pneumatic dredgers (Airlift) and bioremediation, where marine microorganisms that degraded phenol were summarized, as well as future research needs. This study provided a guidance for emergency response and policy development of phenol spills.

Nexus of food waste and climate change framework: Unravelling the links between impacts, projections, and emissions

This communication explores the intricate relationship between food waste and climate change, considering aspects such as impacts, projections, and emissions. It focuses on the pressing issue of waste generation and its potential consequences if current trends persist, and emphasises the importance of efficient solid waste management in improving environmental quality and fostering economic development. It also highlights the challenges faced by developing countries in waste collection and disposal, drawing comparisons with the waste utilisation methods used by developed nations. The review delves into the link between food waste and climate change, noting the paradoxical situation of food wastage against the backdrop of global hunger and malnutrition. It underscores the scientific evidence connecting food waste to climate change and its implications for food security and climate systems. Additionally, it examines the environmental burden imposed by food waste, including its contribution to greenhouse gas emissions and the depletion of resources such as energy, water, and land. Besides environmental concerns, this communication also highlights the ethical and socioeconomic dimensions of food waste, discussing its influence on Sustainable Development Goals, poverty, and social inequality. The communication concludes by advocating for collective action and the development of successful mitigation strategies, technological solutions, and policy interventions to address food waste and its climate impacts. It emphasises the need for collaboration, awareness, and informed decision-making to ensure a more sustainable and equitable future.

Impact of gradually-achieved high phenol loads on the nitrification and COD removal performance of an MBBR fed with synthetic wastewater

Phenol is a noteworthy pollutant, found in effluents of many industrial processes, like oil refining and drugs production, which can impair the treatment efficiency of bioreactors. This study evaluated the performance of phenol, COD, and nitrogen removal of an aerobic bench-scale Moving Bed Biofilm Reactor (MBBR) exposed to gradually increasing phenol content over 233 days. The reactor had Hydraulic Retention Time (HRT) set at 3 h and 40% filling degree (K1 media), and was fed with synthetic wastewater containing phenol (10, 20, 50, 100, 250 and 400 mg/L), glucose (400 mgCOD/L), and 40 mgN-NH3/L. Phenol, COD, and ammoniacal nitrogen removal averages were high - above 88%, 81%, and 82%, respectively -, even when the MBBR was exposed to the greatest phenol loads, indicating that the biofilm was able to acclimate and resist high phenol concentrations. However, the intense EPS production revealed the impact caused by phenol to the biofilm from the concentration of 250 mg/L onwards. Even though, at this concentration, the average removals of COD and phenol were 87.2% and 89.7%. The removal of ammoniacal nitrogen by nitrification was compromised, being 91.6% of the ammoniacal nitrogen removed by assimilation and only 0.35% removed by nitrification. At 400 mg phenol/L, the reactor provided COD and phenol average removals equal 88.6% and 80.9%, respectively. On the last day of operation, the removal of COD dropped to 55.4% and phenol removal was equal 49.0%. Novel microscopical evaluation of the MBBR's biofilm revealed some negative effects of the phenol on the microbiota composition.

A novel comprehensive strategy for high-thoroughly studying released compounds during the combustion process of herbs. A case study for Artemisia argyi Levl. et Vant

The comprehensive study of compound variations in released smoke during the combustion process is a great challenge in many scientific fields related to analytical chemistry like traditional Chinese medicine, environment analysis, food analysis, etc. In this work, we propose a new comprehensive strategy for efficiently and high-thoroughly characterizing compounds in the online released complex smokes: (i) A smoke capture device was designed for efficiently collecting chemical constituents to perform gas chromatography-mass spectrometry (GC-MS) based untargeted analysis. (ii) An advanced data analysis tool, AntDAS-GCMS, was used for automatically extracting compounds in the original acquired GC-MS data files. Additionally, a GC-MS data analysis guided instrumental parameter optimizing strategy was proposed for the optimization of parameters in the smoke capture device. The developed strategy was demonstrated by the study of compound variations in the smoke of traditional Chinese medicine, Artemisia argyi Levl. et Vant. The results indicated that more than 590 components showed significant differences among released smokes of various moxa velvet ratios. Finally, about 88 compounds were identified, of which phenolic compounds were the most abundant, followed by aromatics, alkenes, alcohols and furans. In conclusion, we may provide a novel approach to the studies of compounds in online released smoke.

Quantitative structure-activity relationships for the reaction kinetics of trace organic contaminants with one-electron oxidants

Understanding the reactivity between trace organic contaminants (TrOCs) and radicals involved in advanced oxidation processes (AOPs) is necessary for a good process design, but the experimentally determined rate constants (k values) are not sufficient for numerous artificial TrOCs. Thus, the development of quantitative structure-activity relationships (QSARs) for predicting k values may be an effective way to address this limitation. In this work, we developed QSARs for the reactions of TrOCs with AOP-related one-electron oxidants. Specifically, 15 QSARs using Hammett constants and 8 cross-correlations were developed based on the k values of over 400 reactions between TrOCs (most contain electron-rich moieties, such as phenol, aniline, and alkoxy benzene) and 5 one-electron oxidants (SO4˙-, Br˙, Br2˙-, Cl2˙-, and CO3˙-). Overall, the developed QSARs show a good predictive performance with 94% (237/251, for Hammett constant-based QSARs) and 80% (218/274, for cross-correlations) of the k values predicted within a factor of 3. All the Hammett constant-based QSARs show negative slope values and all cross-correlations show positive relationships, suggesting all 5 one-electron oxidants mainly share similar electrophilic mechanisms with the TrOCs highlighted in this work. Previous QSAR studies on the k values of one-electron oxidants were compared and integrated into their model analysis. Furthermore, k values predicted herein from the QSARs were used to evaluate the degradation of TrOCs during UV/persulfate and UV/chlorine treatment in multiple wastewater matrices, which were demonstrated to be useful. Finally, remarks on the use of the developed QSARs were presented.

A review on recent advancements in extraction, removal and recovery of phenols from phenolic wastewater: Challenges and future outlook

Water pollution is the major problem seen in today's scenario and even pollutants at low concentration harms our environment. In industrial sector usage of phenol is seen even at low concentrations. The interaction of phenol in the environment provides adverse effects to living beings. This review focuses on the toxicity of phenol and its impact towards environment and human health. The treatment techniques such as distillation, extraction, wet air oxidation, membrane process, electrochemical oxidation, biological treatment and finally adsorption techniques were discussed. Among many treatment techniques so far utilized in the treatment of phenol, adsorption was considered as one of the best technique due to its advantages such as reusability, ease in operation, large availability etc., This review also highlights the adsorption technique for the cleaner removal of phenol from aqueous solution with novel as well as low-cost adsorbents in the removal of phenolic compounds. This review also discusses about the drawbacks and issues related with adsorption of phenolic compounds.

A critical review on the removal of toxic pollutants from contaminated water using magnetic hybrids

The persistence of organic/inorganic pollutants in the water has become a serious environmental issue. Among the different pollutants, dyes and heavy metal pollution in waterways are viewed as a global ecological problem that can have an impact on humans, plants, and animals. The necessity to develop a sustainable and environmentally acceptable approach to remove these toxic contaminants from the ecosystem has been raised. In the past two decades, rapid industrialization and anthropogenic activities in developed countries have aggravated environmental pollution. Industrial effluents that are discharged directly into the natural environment taint the water, which has a consequence for the water resources. Magnetic nanohybrids are broadly investigated materials used in the adsorption and photocatalytic degradation of poisonous pollutants present across water effluents. In the present review, the toxic health effects of heavy metals and dyes from the water environment have been discussed. This paper reviews the role of magnetic nanohybrids in the removal of pollutants from the water environment, providing an adequate point of view on their new advances regarding their qualities, connection methodologies, execution, and their scale-up difficulties.

Effects of o-cresol on the growth and biochemical compositions in marine microalgae

To assess the toxic effects of o-cresol on marine organisms, Skeletonema costatum and Phaeodactylum tricornutum were chosen as test subjects to investigate its impact on growth and biochemical compositions. The results indicated that the 96-h EC50 values for o-cresol in S. costatum and P. tricornutum were 7.99 mg/L and 13.28 mg/L, respectively, demonstrating a moderate and slight toxicity level. Conversely, the maximum no-effect concentration (NOEC) for o-cresol in S. costatum and P. tricornutum were 2.43 mg/L and 0.43 mg/L, respectively, classifying their chronic toxicity grades as negligible and low toxic. Following a 96-h exposure period, the content of photosynthetic pigments in S. costatum did not significantly differ from the control group (P > 0.05). Conversely, the levels of total protein, total lipid, and carbohydrate in microalgae were significantly induced (P < 0.05) as the concentration of o-cresol increased. Higher concentrations of o-cresol generally stimulated the synthesis of biochemical compositions in algae cells, which serves as an active defense mechanism in response to pollution stress. To comprehensively evaluate the potential risk of o-cresol to marine ecosystems, it is crucial to strengthen its toxicity studies on marine fish and crustaceans in the future.

Co(II)-Based Metal-Organic Framework Derived CA-CoNiMn-CLDHs with Peroxidase-like Activity for Colorimetric Detection of Phenol

Given the serious harm of toxic phenol to human health and the ecological environment, it is urgent to develop an efficient, low-cost and sensitive nanoenzyme-based method to monitor phenol. MOF-derived nanozyme has attracted wide interest due to its hollow polyhedra structure and porous micro-nano frameworks. However, it is still a great challenge to synthesize MOF-derived multimetal synergistic catalytic nanoenzymes in large quantities with low cost. Herein, we reported the synthetic strategy of porous hollow CA-CoNiMn-CLDHs with ZIF-67 as templates through a facile solvothermal reaction. The prepared trimetallic catalyst exhibits excellent peroxidase-like activity to trigger the oxidative coupling reaction of 4-AAP and phenol in the presence of H2O2. The visual detection platform for phenol based on CA-CoNiMn-CLDHs is constructed, and satisfactory results are obtained. The Km value for CA-CoNiMn-CLDHs (0.21 mM) is lower than that of HRP (0.43 mM) with TMB as the chromogenic substrate. Because of the synergistic effect of peroxidase-like activity and citric acid functionalization, the built colorimetric sensor displayed a good linear response to phenol from 1 to 100 μM with a detection limit of 0.163 μM (3σ/slope). Additionally, the CA-CoNiMn-CLDHs-based visual detection platform possesses high-chemical stability and excellent reusability, which can greatly improve economic benefits in practical applications.

Development of methods based on low-temperature partitioning (LTP) for monitoring cresols and chlorophenols in sewage sludge, soil, and water in column leaching

Cresols and chlorophenols are chemical contaminants that are potentially toxic to humans and can be found in sewage sludge. These chemical contaminants can migrate into the sludge-soil-water system when sludge is used as a conditioner for agricultural soils. Thus, the objective of this study was to develop methodologies based on extraction with low-temperature partitioning (LTP) to determine cresols and chlorophenols in sewage sludge, soil, and water. The analysis was performed by gas chromatography coupled with mass spectrometry (GC-MS). The validated methods were applied to monitor cresols and chlorophenols in a column-leaching study of a sludge-soil-water system. Satisfactory results were achieved for selectivity, limit of quantification (LOQ), linearity, accuracy, and precision. In the column leaching study, only 2,4,6-trichlorophenol was quantified in sludge samples after 20 days of the experiment. None of the studied compounds were quantified in soil and leached water samples, due to the degradation promoted by the microorganisms present in the sewage sludge. Finally, validated methods were suitable for monitoring cresols and chlorophenols in the sludge-soil-water system.

Aquatic toxicity of hydroquinone and catechol following metal oxide treatment to Ceriodaphnia dubia and Pimephales promelas

Metal oxides comprise a large group of chemicals used in water treatment to adsorb organic pollutants. The ability of titanium dioxide (TiO₂) and iron (III) oxide (Fe₂O₃) to reduce the chronic toxicity of (phenolic) C₆H₆(OH)₂ isomers, namely hydroquinone (HQ) and catechol (CAT) to Ceriodaphnia dubia and Pimephales promelas (less than 24 h-old) were investigated. The toxic endpoints following metal oxide treatment were compared to endpoints of untreated CAT and HQ. In chronic toxicity testing, HQ resulted in greater toxicity than CAT for both test organisms; the median lethal concentrations (LC₅₀) for CAT were 3.66 to 12.36 mg.L^-1 for C. dubia and P. promelas, respectively, while LC₅₀ for HQ were 0.07 to 0.05 mg.L^-1, respectively. Although both treated solutions presented lower toxic endpoints than those in the untreated solutions, Fe₂O₃ had a better potential to reduce the toxic effects of CAT and HQ than TiO₂.

Construction of Bio-TiO2/Algae Complex and Synergetic Mechanism of the Acceleration of Phenol Biodegradation

Microalgae have been widely employed in water pollution treatment since they are eco-friendly and economical. However, the relatively slow treatment rate and low toxic tolerance have seriously limited their utilization in numerous conditions. In light of the problems above, a novel biosynthetic titanium dioxide (bio-TiO₂ NPs)-microalgae synergetic system (Bio-TiO₂/Algae complex) has been established and adopted for phenol degradation in the study. The great biocompatibility of bio-TiO₂ NPs ensured the collaboration with microalgae, improving the phenol degradation rate by 2.27 times compared to that with single microalgae. Remarkably, this system increased the toxicity tolerance of microalgae, represented as promoted extracellular polymeric substances EPS secretion (5.79 times than single algae), and significantly reduced the levels of malondialdehyde and superoxide dismutase. The boosted phenol biodegradation with Bio-TiO₂/Algae complex may be attributed to the synergetic interaction of bio-TiO₂ NPs and microalgae, which led to the decreased bandgap, suppressed recombination rate, and accelerated electron transfer (showed as low electron transfer resistance, larger capacitance, and higher exchange current density), resulting in increased light energy utilization rate and photocatalytic rate. The results of the work provide a new understanding of the low-carbon treatment of toxic organic wastewater and lay a foundation for further remediation application.

Evaluation of Bacillus aryabhattai B8W22 peroxidase for phenol removal in waste water effluents

Environmental contamination by phenol has been reported in both aquatic and atmospheric environments. This study aimed to separate and purify the peroxidase enzyme from bacteria that degrade phenol from wastewater sources. An enrichment culture of MSM was used to screen 25 bacterial isolates from different water samples for peroxidase production, six of the isolates exhibited high levels of peroxidase enzyme activity. Qualitative analysis of peroxidase revealed that isolate No. 4 had the highest halo zones (Poly-R478: 14.79 ± 0.78 mm, Azure B: 8.81 ± 0.61 mm). The promising isolate was identified as Bacillus aryabhattai B8W22 by 16S rRNA gene sequencing with accession number OP458197. As carbon and nitrogen sources, mannitol and sodium nitrate were utilized to achieve maximum peroxidase production. A 30-h incubation period was used with pH 6.0, 30 °C, mannitol, and sodium nitrate, respectively, for maximal production of peroxidase. Purified peroxidase enzyme showed 0.012 U/mg specific activity, and SDS-PAGE analysis indicated a molecular weight of 66 kDa. The purified enzyme exhibits maximum activity and thermal stability at pH values of 4.0 and 8.0, respectively, with maximum activity at 30 °C and complete thermal stability at 40 °C. In the purified enzyme, the Km value was 6.942 mg/ml and the Vmax value was 4.132 mol/ml/hr, respectively. The results demonstrated that Bacillus aryabhattai B8W22 has promising potential for degrading phenols from various phenol-polluted wastewater sources.

Isolation and characterization of Indigenous Bacilli strains from an oil refinery wastewater with potential applications for phenol/cresol bioremediation

Phenolic compounds are frequently occurring in wastewaters from various industrial processes at high concentrations, imposing prominent risk to aquatic biosphere and human health. Bioremediation has been proven to be an effective approach to remove these compounds, and hunting for functional organisms is still of primary importance to develop efficient processes. In this study, we report several newly isolated bacillus strains with superior performances in metabolizing phenols, one of which showed paramount efficiencies to metabolize phenol at concentrations up to 1200 mg L^-1 and could simultaneously degrade a wide range of other phenolic compounds. The genes encoding for phenol hydroxylase (PH) and catechol-2,3-dioxygenase (C23O) have been detected and characterized, evidencing that phenol degradation occurs via the meta pathway. The GC level of the PH gene was found to be much higher than that of genes from other Bacilli but was quite close to that of the genes from Rhodococcus, and the induction of both enzymes by phenols was confirmed by RT-PCR experiments. We intend to believe this novel strain might be promising to serve as preferred organisms for developing more robust and efficient bioremediation processes of degrading phenolic compounds due to its validated performance.

Syringol, a wildfire residual methoxyphenol causes cytotoxicity and teratogenicity in zebrafish model

Natural toxicants, particularly methoxy phenols (MPs) generated by wildfire lignin, can accumulate in the environment, and cause serious health hazards in living organisms. Although the toxicity of MPs such as guaiacol and catechol has recently been described, there is minimal evidence of ecotoxicological effects of syringol. As a result, this study focuses on determining the toxicity by evaluating the cytotoxic and teratogenic effects of syringol in vitro and in vivo in human embryonic kidney (HEK-293) cells and zebrafish embryos, respectively. The ecotoxicity of syringol was predicted to be 63.8 mg/L using the ECOSAR (ECOlogical Structure Activity Relationship) prediction tool, and molecular docking analysis was used to determine the interaction and binding affinities of syringol with human apoptotic proteins in silico. In HEK-293 cells, exposure of syringol (0.5-2 mg/L) has induced cytotoxicity in a concentration-dependent manner. In zebrafish larvae, exposure of syringol (0.5-2 mg/L) has induced dose-dependent embryo toxic effects (or growth abnormalities such as yolk sac edema, pericardial edema, skeletal abnormality, and hyperemia), and changes in growth morphometrics (head height, eye, yolk sac, and pericardial area, heart rate) in particular, the heart rate of larvae was found to be significantly decreased (p<0.001). After a 4-day experimental trial, the accumulated concentration of syringol in zebrafish larvae was confirmed both qualitatively (HPLC-MS - High Performance Liquid Chromatography-Mass spectrometry) and quantitatively (LC-QTOF-HRMS - Liquid Chromatography-Quadrupolar Time of Flight-High Resolution Mass spectrometry). The craniofacial abnormalities induced by syringol exposure (0.5-2 mg/L) were detected as anomalies in cartilaginous development and locomotor deficits using alcian blue staining and locomotor analyses, respectively. Significant increase in oxidative stress parameters (including reactive oxygen species generation, lipid peroxidation, superoxide dismutase, catalase, lactate dehydrogenase and nitric oxide production) (p<0.001) and substantial decrease in glutathione levels were observed (p<0.05) in syringol exposed zebrafish larvae through enzymatic analysis. Additionally, through acridine orange staining and gene expression analyses, syringol (2 mg/L) was found to activate apoptosis in zebrafish larvae. Considering the cytotoxic, embryotoxic (teratogenicity), and oxidative stress-related apoptotic effects of syringol in the zebrafish model, syringol has the potential to emerge as a potent environmental toxicant posing serious health hazards in many living systems; however, further research on its toxicological effects on the actual ecosystem and in higher animal models is required to confirm its consequences.

Use of tyrosinase-inorganic salt hybrid nanoflowers and tyrosinase-MOF hybrid composites for elimination of phenolic pollutants from industrial wastewaters

Removal of phenolic pollutants from industrial wastewaters is always an important practical problem. Use of enzymes for dephenolization provides a green solution. In this work, enzymatic methods were developed by employing mushroom tyrosinase immobilized as enzyme-Cu₃(PO₄)₂ hybrid nanoflowers and enzyme-metal organic framework (i.e., ZIF-8 and HKUST-1) hybrid composites, which were shown to be superior to processes mediated by tyrosinase immobilized on other supports in both dephenolization efficiency and reusability. Comparatively, tyrosinase@Cu₃(PO₄)₂ and tyrosinase@HKUST-1 were better than tyrosinase@ZIF-8 in both specific activity and dephenolization efficiency. Typical phenolic pollutants, including 3 monophenols (phenol, p-cresol, p-chlorophenol) and 3 bisphenols (BPA, BPB, BPF), can be completely eliminated within 0.5-4 h. The dephenolization order was discussed based on the enzyme's substrate specificity. The operability and reusability of these hybrid biocomposites were highly improved by entrapping into alginate gels or by incorporating with modified magnetic Fe₃O₄ nanoparticles. Particularly, the magnetic biocatalyst was prepared via a facile one-pot/one-step de novo synthetic strategy, optimized by using response surface methodology (RSM). The as-prepared magnetic tyrosinase@mHKUST-1 retained a high dephenolization efficiency of 81% after 10 cycles and was effective for continuous dephenolization for at least 24 h. These hybrid biocomposites were also successfully applied to treatment of real industrial wastewater from a coke plant.

New insight into the mechanism of ferric hydroxide-based heterogeneous Fenton-like reaction

The heterogeneous Fenton-like reaction (HeFR) has always been a research focus for environmental applications. However, it has long been difficult to reach a consensus on the reaction mechanism because the process of metal ions dissolution and its role were not well understood. In this paper, we propose the courses of organics-mediated coordination or/and reduction dissolution of ferric hydroxide to initiate the autocatalytic kinetics of phenol degradation and illustrate it through density functional theory (DFT) and experiments. With the increase of hydrogen peroxide concentration, the degradation of phenol changes from autocatalytic kinetics to first-order kinetics. Furthermore, a novel "limit segmentation method" initiated by us indicates that homogeneous reaction plays a decisive role in the phenol degradation process. The dominant roles of the reactive organics in both iron dissolution and the iron cycle and of the homogeneous reaction in the whole degradation process in the ferric hydroxide-based HeFR system are brand-new insights that pave the pathway for future research.

Mixture Toxicity of Three Unconventional Gas Fracking Chemicals, Barium, O-Cresol, and Sodium Chloride, to the Freshwater Shrimp Paratya australiensis

The 96-h acute toxicity of barium (Ba²⁺ ), o-cresol, and sodium chloride (NaCl) to Paratya australiensis was assessed in single, binary, and ternary combinations in addition to three biochemical assays: glutathione S-transferase, acetylcholinesterase, and sodium-potassium adenosine triphosphatase. The 96-h lethal concentrations that expressed 50% mortality (LC50) in the single-toxicant exposures were Ba²⁺  = 23.4 mg/L, o-cresol = 12.2 mg/L, and NaCl = 4198 mg/L. Mortality from o-cresol exposure occurred between 11 and 22 mg/L, whereas Ba²⁺ was more gradual across 10-105 mg/L, and most of the NaCl mortality occurred between 2050 and 4100 mg/L. Toxic units were used to assess the binary and ternary interactions of the toxicants. A more than additive effect was observed for most combinations in the binary chemical exposures, with the ternary combinations yielding highly synergistic interactions. Greater synergism was observed with the 96-h LC50 of o-cresol in combination with the three concentrations of NaCl (1025, 2050, and 3075 mg/L) compared with Ba²⁺ , with toxic units of 0.38, 0.48, and 0.10 (o-cresol) and 0.71, 0.67, and 0.50 (Ba²⁺ ). No notable enzyme activity trends were observed in the enzyme biomarker responses from both individual and mixture exposures. Although acute single-species toxicity tests tend to underestimate the effects of Ba²⁺ , o-cresol, and NaCl on populations, communities, and ecosystems in seminatural (e.g., mesocosms) and natural systems, there are currently no published acute toxicity data available for P. australiensis and the three toxicants used in the present study. The present study shows that chemicals with different toxicity mechanisms can potentially lead to more synergistic responses. Environ Toxicol Chem 2023;42:481-494. © 2022 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

Enhanced prediction of internal concentrations of phenolic endocrine disrupting chemicals and their metabolites in fish by a physiologically based toxicokinetic incorporating metabolism (PBTK-MT) model

Bisphenol A (BPA), 4-nonylphenol (4-NP), and triclosan (TCS) are phenolic endocrine disrupting chemicals (EDCs), which are widely detected in aquatic environments and further bioaccumulated and metabolized in fish. Physiologically based toxicokinetic (PBTK) models have been used to describe the absorption, distribution, metabolism, and excretion (ADME) of parent compounds in fish, whereas the metabolites are less explored. In this study, a PBTK incorporating metabolism (PBTK-MT) model for BPA, 4-NP, and TCS was established to enhance the performance of the traditional PBTK model. The PBTK-MT model comprised 16 compartments, showing great accuracy in predicting the internal concentrations of three compounds and their glucuronidated and sulfated conjugates in fish. The impact of typical hepatic metabolism on the PBTK-MT model was successfully resolved by optimizing the mechanism for deriving the partition coefficients between the blood and liver. The PBTK-MT model exhibited a potential data gap-filling capacity for unknown parameters through a backward extrapolation approach of parameters. Model sensitivity analysis suggested that only five parameters were sensitive in at least two PBTK-MT models, while most parameters were insensitive. The PBTK-MT model will contribute to a well understanding of the environmental behavior and risks of pollutants in aquatic biota.

Cooperation of multiple active species generated in hydrogen peroxide activation by iron porphyrin for phenolic pollutants degradation

The narrow acid pH range and the nonselectivity of the dominant •OH limit the Fenton systems to remediate the organic wastewater. Inspired by the role of heme in physiological processes, we employed iron porphyrin as a novel homogeneous catalyst to address this issue. Multiple active species are identified during the activation of H₂O₂, including high-valent iron porphyrin ((por)Fe(IV)) species ((por)Fe(IV)-OH, (por)^+•Fe(IV)=O) and oxygen-centered radicals (•OH, HO₂•/•O₂^-), as well as atomic hydrogen (*H) and carbon-centered radicals. With the cooperation of these active species, the degradation of pollutants could be resistant to the interference of concomitant ions and proceed over a wide pH range. This cooperative behavior is further verified by intermediates identified from bisphenol A degradation. Specifically, the presence of *H could facilitate the cleavage of the C-C bond and the addition of unsaturated or aromatic molecules. (Por)^+•Fe(IV)=O could hydroxylate substrates with an oxygen rebound mechanism. Hydrogen atom abstraction of contaminants could be performed by (por)Fe(IV)-OH to form desaturated products by attacking oxygen-centered radicals. The ecotoxicity of bisphenol A could be significantly decreased through degradation. This study would provide a new approach to wastewater treatment and shed light on the interaction between metalloporphyrin and peroxide in an aqueous solution.

The role of TiO2 NPs catalyst and packing material in removal of phenol from wastewater using an ozonized bubble column reactor

Phenol is present as a highly toxic pollutant in wastewater, and it has a dangerous impact on the environment. In the present research, the phenol removal from wastewater has been achieved using four treatment methods in a bubble column reactor (treatment by ozone only, using packed bubble column reactor with ozone, utilizing ozone with TiO2 NPs catalyst in the reactor without packing, and employing ozone with TiO2 NPs in the presence of packing). The effects of phenol concentration, ozone dosage, TiO2 NPs additions, and contact time on the phenol removal efficiency were determined. It was found that at a contact time of 30 min, the phenol removal was 60.4, 74.9, 86.0, and 100% for the first, second, third, and fourth methods, respectively. The results indicated that the phenol degradation method using catalytic ozonation in a packed bubble column with TiO2 NPs is the best treatment method. This study demonstrated the advantages of using packing materials in a bubble column reactor to enhance the mass transfer process in an ozonation reaction and then increase the phenol removal efficiency. Also, the presence of TiO2 NPs as a catalyst improves the ozonation process via the production of hydroxyl routs. Additionally, the reaction kinetics of ozonation reaction manifested that the first order model is more applicable for the reaction. Eventually, the packed bubble column reactor in the presence of TiO2 NPs catalyst provided a highperformance removal of phenol with a high economic feasibility.

Determination of p-cresol levels in smoked meat products using QuEChERS method and gas chromatography-mass spectrometry

p-Cresol is known as an environmental chemical contaminant that has toxic effects on humans. However, the presence of p-cresol in smoked foods has been seen as a flavor constituent. The present study had as objective to optimize and validate the QuEChERS method for the determination of p-cresol in beef hamburger, which was chosen as a representative matrix for six smoked meat products. The analysis was performed by gas chromatography coupled with mass spectrometry (GC-MS). The method showed limit of quantification (LOQ) of 40 µg kg^-1, linearity between 40 and 200 µg kg^-1, recovery higher than 70% and relative standard deviation lower than 14%. The proposed method was applied to six different smoked foods and the p-cresol concentration ranged from 148 to 872 µg kg^-1 and only the turkey breast pate showed a concentration lower than the LOQ. The descending order of p-cresol level in smoked samples was: sausage > shredded tuna > salami > turkey breast > hamburger > turkey breast pate. In three analyzed samples, the results showed that the p-cresol migrates from the surface to the food inner. Finally, the proposed method was simple and efficient to quantify high levels of this contaminant in smoked foods and it could be a useful tool for the monitoring food safety and quality.

Biodegradation modeling of phenol using Curtobacterium flaccumfaciens as plant-growth-promoting bacteria

Phenol is a major worry pollutant resulting from industrialized manufacturing and chemical reactions. The growth kinetics and biodegradation of phenol were initially investigated using C. flaccumfaciens, a recently identified plant growth stimulating bacterium. Based on the Haldane inhibition model, Haldane's growth kinetics inhibition coefficient (Ki), half-saturation coefficient (Ks), and the maximum specific growth rate (max) for phenol-dependent growth kinetics were estimated to be 329 (mg/L), 9.14 (mg/L), and 1.05 (h⁻¹), respectively. With a sum of squared error (SSR) of 1.36 × 10⁻³, the Haldane equation is well adapted to empirical data. The improved Gombertz model also accurately predicts phenol biodegradation trends. The rate of phenol biodegradation and the lag time both increased as the initial phenol concentrations were increased. C. flaccumfaciens growth and phenol biodegradation were best achieved at a pH of 7.0 at a temperature of 28 °C incubation. A phenol biodegradation mechanism by C. flaccumfaciens has been proposed. In conclusion, this study revealed the ability of C. flaccumfaciens to promote plant growth and biodegrade phenol simultaneously. This could aid in rhizoremediation and crop yield preservation in phenol-stressed conditions.

Fabrication of Polyaniline@β-cyclodextrin Nanocomposite for Adsorption of Carcinogenic Phenol from Wastewater

We synthesized a stable, eco-friendly, and low-cost polyaniline@β-cyclodextrin (PANI@β-CD) nanocomposite via oxidative polymerization for phenol adsorption from water waste since phenol pollution is a global danger to human and animal health and the environment. The production of the composite and synergistic alteration of PANI with β-CD resulted in 66% reduction in particle size from 59 nm (PANI) to 20 nm (PANI@β-CD) as well as better phenol adsorption. Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), scanning electron microscope (SEM), and thermogravimetric analysis (TGA) were used to analyze the produced PANI@β-CD nanocomposite. Our results show the optimum conditions for phenol adsorption: time (50 min), pH (8.0), nanosorbent dose (0.5 g), and the sorption isotherm fitted with Langmuir model; the monolayer adsorption capacity of the prepared PANI@β-CD for phenol was determined to be 8.56 mg g-1. The average pore size, total pore volume, and surface area of PANI/βCD nanocomposite are 15.62 nm, 0.1586 cm3/g, and 90.901 m2/g, respectively, for the pseudo second order model. Finally, modifying PANI nanoparticles with βCD allowed reusability up to four cycles with superior adsorption performance of ∼95% using (0.01 N) HNO3.

The first plastic produced, but the latest studied in microplastics research: The assessment of leaching, ecotoxicity and bioadhesion of Bakelite microplastics

Bakelite, the first synthetic plastic, is a rather unexplored material in the field of ecotoxicology, despite its long production and use. The aim of this study was to investigate the ecotoxicity of Bakelite microplastics (before and after leaching) and its leachates on four aquatic organisms: the crustacean Daphnia magna, the plant Lemna minor, the bacterium Allivibrio fischeri and the alga Pseudokirchneriella subcapitata. Bakelite microplastics before and after leaching and leachates affected all organisms, but to varying degrees. Leachates showed increased ecotoxicity to Daphnia magna, while Pseudokirchneriella subcapitata was more affected by particles. For Lemna minor and Allivibrio fischeri, the effects of particles before leaching and leachate were comparable, while the negative effect of particles after leaching was minimal or not present. All leachates were analysed, and phenol and phenol-like compounds were the predominant organics found. In addition, bioadhesion of Bakelite microplastics to the surface of Daphnia magna and Lemna minor was confirmed, but the particles were mainly weakly adhered. Results of this study suggest that, in addition to the recently studied microplastics from consumer products (e.g. from polyethylene and polystyrene), microplastics from industrial plastics such as Bakelite may be of increasing concern, primarily due to leaching of toxic chemicals.

Flower-like molybdenum disulfide decorated ZIF-8-derived nitrogen-doped dodecahedral carbon for electro-catalytic degradation of phenol

In this work, flower-like molybdenum disulfide was constructed on the surface of ZIF-8-derived nitrogen-doped dodecahedral carbon (ZNC) for the electrocatalytic degradation of phenol. The flower-like nanostructure of MoS₂@ZNC contributed to the exposure of more edge-active sites of MoS₂. At the same time, Mo⁴⁺ and Mo⁶⁺ co-existed in MoS₂@ZNC, which promoted the generation of H₂O₂ and •OH, and improved the catalytic activity of composite materials. In addition, electrochemical performance analysis showed that MoS₂ loaded on the surface of ZNC significantly improved the redox capacity of the material, and the composite ratio of MoS₂ and ZNC affected the structure and properties of MoS₂@ZNC composites. Moreover, the electrochemical performance of prepared MoS₂@ZNC was evaluated by the generation of hydroxyl (•OH) and the degradation efficiency of phenol. The results showed that MoS₂@ZNC-2 had an excellent phenol degradation efficiency (98.8%) and COD removal efficiency (86.8%) within 120 min. Furthermore, MoS₂@ZNC cathode still maintained good performance after being experimented with 20 times, indicated the excellent stability of MoS₂@ZNC.

The structure-activity relationship of aromatic compounds in advanced oxidation processes：a review

Advanced oxidation processes (AOPs) are widely used as efficient technologies to treat highly toxic and harmful substances in wastewater. Taking the most representative aromatic compounds (monosubstituted benzenes, substituted phenols and heterocyclic compounds) as examples, this paper firstly introduces their structures and the structural descriptors studied in AOPs before, and the influence of structural differences in AOPs with different reactive oxygen species (ROS) on the degradation rate was discussed in detail. The structure-activity relationship of pollutants has been previously analyzed through quantitative structure-activity relationship (QSAR) model, in which ROS is a very important influencing factor. When electrophilic oxidative species attacks pollutants, aromatic compounds with electron donating groups are more favorable for degradation than aromatic compounds with electron donating groups. While nucleophilic oxidative species comes to the opposite conclusion. The choice of advanced oxidation processes, the synergistic effect of various active oxygen species and the used catalysts will also change the degradation mechanism. This makes the structure-dependent activity relationship uncertain, and different conclusions are obtained under the influence of various experimental factors.

Capacity of Marine Microalga Tetraselmis suecica to Biodegrade Phenols in Aqueous Media

Phenolic compounds are toxic and dangerous to the environment and human health. Although the removal of phenols and their derivatives is very difficult, it has been achieved by applying some biological processes. The capacity of microalga to remove phenolic compounds has been demonstrated; however, few reports of the removal of these compounds in a mixture have been published. The removal of phenol, p-cresol and o-cresol was performed by batch kinetics at 50 and 100 mg L−1, and the simultaneous degradation of phenol, p-cresol and o-cresol was carried out in a mixture at 40 mg L−1 using the marine microalga Tetraselmis suecica. The kinetic study was carried out for 192 h. For concentrations of 50 mg L−1 and 100 mg L−1, phenolic compound consumption efficiencies greater than 100% and 85%, respectively, were obtained, and up to 73.6% removal in the mixture. The results obtained indicate that the marine microalga carries out a process of the oxidation of organic matter and phenolic compounds, mineralizing up to 31.4% to CO2 in the mixture. Biological treatments using the marine microalga T. suecica can be considered feasible to treat effluents with concentrations similar to those of the present study.

Endohedral Gd-Containing Fullerenol: Toxicity, Antioxidant Activity, and Regulation of Reactive Oxygen Species in Cellular and Enzymatic Systems

The Gd-containing metallofullerene derivatives are perspective magnetic resonance imaging contrast agents. We studied the bioeffects of a water-soluble fullerene derivative, gadolinium-endohedral fullerenol, with 40−42 oxygen groups (Gd@Fln). Bioluminescent cellular and enzymatic assays were applied to monitor toxicity and antioxidant activity of Gd@Fln in model solutions; bioluminescence was applied as a signaling physiological parameter. The Gd@Fln inhibited bioluminescence at high concentrations (>2·10−1 gL−1), revealing lower toxicity as compared to the previously studied fullerenols. Efficient activation of bioluminescence (up to almost 100%) and consumption of reactive oxygen species (ROS) in bacterial suspension were observed under low-concentration exposure to Gd@Fln (10−3−2·10−1 gL−1). Antioxidant capability of Gd@Fln was studied under conditions of model oxidative stress (i.e., solutions of model organic and inorganic oxidizers); antioxidant coefficients of Gd@Fln were determined at different concentrations and times of exposure. Contents of ROS were evaluated and correlations with toxicity/antioxidant coefficients were determined. The bioeffects of Gd@Fln were explained by hydrophobic interactions, electron affinity, and disturbing of ROS balance in the bioluminescence systems. The results contribute to understanding the molecular mechanism of “hormetic” cellular responses. Advantages of the bioluminescence assays to compare bioeffects of fullerenols based on their structural characteristics were demonstrated.

Co-metabolic biodegradation of 4-bromophenol in a mixture of pollutants system by Arthrobacter chlorophenolicus A6

Brominated phenols are listed as priority pollutants together with nitrophenol and chlorophenol are the key components of paper pulp wastewater. However, the biodegradation of bromophenol in a mixed substrate system is very scanty. In the present investigation, simultaneous biodegradation kinetics of three substituted phenols 4-bromophenol (4-BP), 4-nitrophenol (4-NP), and 4-chlorophenol (4-CP) were investigated using Arthrobacter chlorophenolicus A6. A 2³ full factorial design was applied with varying 4-BP and 4-CP from 75-125 mg/L and 4-NP from 50-100 mg/L. Almost complete degradation of this mixture of substituted phenols was achieved at initial concentration combinations of 125, 125, and 100 mg/L of 4-CP, 4-BP, and 4-NP, respectively, in 68 h. Statistical analysis of the results revealed that, among the three variables, 4-NP had the most prominent influence on the degradation of both 4-CP and 4-BP, while the concentration of 4-CP had a strong negative interaction effect on the biodegradation of 4-NP. Irrespective of the concentration levels of these three substrates, 4-NP was preferentially biodegraded over 4-CP and 4-BP. Furthermore, 4-BP biodegradation rates were found to be higher than those of 4-CP, followed by 4-NP. Besides, the variation of the biomass yield coefficient of the culture was investigated at different initial concentration combinations of these substituted phenols. Although the actinomycetes consumed 4-NP at a faster rate, the biomass yield was very poor. This revealed that the microbial cells were more stressed when grown on 4-NP compared to 4-BP and 4-CP. Overall, this study revealed the potential of A. chlorophenolicus A6 for the degradation of 4-BP in mixed substrate systems.

Evaluating the consequences of household hazardous waste diversion on public health and ecological risks of leachate exposure

Household hazardous waste (HHW) includes approximately 1% of municipal solid waste (MSW), which is related to the lack of efficient separate collection schemes co-disposed with MSW in many countries worldwide. In this research, the effect of HHW diversion on leachate quality and consequent reduction in risks to the environment and human health was investigated. In this regard, physicochemical parameters of MSW leachate samples with and without hazardous fraction were characterized. Next, leachate pollution index (LPI) and associated risks were assessed. The results showed that the source separation of HHW decreases the LPI value by 13.48% and improves the potential of leachate for biological treatment, leading to a reduction in leachate treatment costs and complexity. Based on risk assessment results, HHW diversion could lower cancer risks of organic compounds and heavy metals to acceptable levels for adults and children. Moreover, by the source-separating of HHW, hazard indices for aquatic and terrestrial bioassays reduced by 41.5 and 36%, respectively. Furthermore, despite the comparatively low generated amount of HHW, this fraction should be emphasized due to its unintended effects for public health and the environment.

Bioremediation of phenolic pollutants by algae - current status and challenges

Industrial production processes, especially petroleum processing, will produce high concentration phenolic wastewater. Traditional wastewater treatment technology is costly and may lead to secondary pollution. In order to avoid the adverse effects of incompletely treated phenolics, more advanced methods are required. Algae bioremediate phenolics through green pathways such as adsorption, bioaccumulation, biodegradation, and photodegradation. At the same time, the natural carbon fixation capacity of algae and its potential to produce high-value products make algal wastewater treatment technology economically feasible. This paper reviews the environmental impact of several types of phenolic pollutants in wastewater and different strategies to improve bioremediation efficiency. This paper focuses on the progress of algae removing phenols by different mechanisms and the potential of algae biomass for further biofuel production. This technology holds great promise, but more research on practical wastewater treatment at an industrial scale is needed in the future.

Effects of olive mill waste (OMW) contaminated soil on biochemical biomarkers and reproduction of Dendrobaena veneta

Olive oil industry is economically important in Mediterranean countries. Disposal of olive mill waste (OMW) presents an environmental concern in those countries due to its high salinity and its high level of polyphenols. In order to reuse OMW, those properties have to change either through the filtration process and addition of adsorbents or by composting. One of the most important organisms in composting of organic wastes is earthworms. However, data on the effects of OMW on earthworms are scarce. The main aim of our study was to investigate whether OMW contaminated soil (OMW CS) causes adverse effects on molecular and organism level in epigeic earthworm Dendrobaena veneta and on microbiological activity. Changes of measured biochemical biomarkers (AChE, CAT, GST, lipids, MDA) varied depending on the quantity of added OMW CS and the exposure duration. Oxidative stress occurred after 7 days of exposure, while in most cases enzyme activity recovered after 28 days. At the highest ratio of contaminated soil (50%), reproduction was completely inhibited. The second aim was to investigate the impact of earthworms on phenol degradation and microbial activity, indicating an important role in the bioremediation of contaminated soils. Our results show that above a certain quantity an OMW CS has an adverse effect on earthworms, while the impact of earthworms on soil microbial activity was positive but transient. Yet, as the results also imply that earthworms have an impact on phenol degradation, they can be used to help remediation of OMW CS and its subsequent usage in agriculture. However, the quantity of OMW CS that can be safely added should be determined first.

Comprehensive characterization of the bacterial community structure and metabolite composition of food waste fermentation products via microbiome and metabolome analyses

Few studies have characterized the microbial community and metabolite profile of solid food waste fermented products from centralized treatment facilities, which could potentially be processed into safe animal feeds. In this study, 16S rRNA gene sequencing and liquid/gas chromatography-mass spectrometry were conducted to investigate the bacterial community structure and metabolite profile of food waste samples inoculated with or without 0.18% of a commercial bacterial agent consisting of multiple unknown strains and 2% of a laboratory-made bacterial agent consisting of Enterococcus faecalis, Bacillus subtilis and Candida utilis. Our findings indicated that microbial inoculation increased the crude protein content of food waste while reducing the pH value, increasing lactic acid production, and enhancing aerobic stability. Microbial inoculation affected the community richness, community diversity, and the microbiota structure (the genera with abundances above 1.5% in the fermentation products included Lactobacillus (82.28%) and Leuconostoc (1.88%) in the uninoculated group, Lactobacillus (91.85%) and Acetobacter (2.01%) in the group inoculated with commercial bacterial agents, and Lactobacillus (37.11%) and Enterococcus (53.81%) in the group inoculated with homemade laboratory agents). Microbial inoculation reduced the abundance of potentially pathogenic bacteria. In the metabolome, a total of 929 substances were detected, 853 by LC-MS and 76 by GC-MS. Our results indicated that inoculation increased the abundance of many beneficial metabolites and aroma-conferring substances but also increased the abundance of undesirable odors and some harmful compounds such as phenol. Correlation analyses suggested that Leuconostoc, Lactococcus, and Weissella would be promising candidates to improve the quality of fermentation products. Taken together, these results indicated that inoculation could improve food waste quality to some extent; however, additional studies are required to optimize the selection of inoculation agents.