Chicken poultry industry produces a vast amount of feather waste and is often disposed into landfills, creating environmental pollution. Therefore, we explored the valorization of chicken feather waste into lipids and keratinous sludge biomass. This study demonstrates the successful utilization of keratinous sludge biomass as a unique precursor for the facile preparation of novel keratinous sludge biomass-derived carbon-based molybdenum oxide (KSC@MoO₃) nanocomposite material using two-step (hydrothermal and co-pyrolysis) processes. The surface morphology and electrochemical properties of as-prepared nanocomposite material were analyzed using HR-SEM, XRD, XPS, and cyclic voltammetric techniques. KSC@MoO₃ nanocomposite exhibited prominent electrocatalytic behavior to simultaneously determine hydroquinone (HQ) and catechol (CC) in environmental waters. The as-prepared electrochemical sensor showed excellent performance towards the detection of HQ and CC with broad concentration ranges between 0.5–176.5 μM (HQ and CC), and the detection limits achieved were 0.063 μM (HQ) and 0.059 μM (CC). Furthermore, the developed modified electrode has exhibited excellent stability and reproducibility and was also applied to analyze HQ and CC in environmental water samples. Results revealed that chicken feather waste valorization could result in sustainable biomass conversion into a high-value nanomaterial to develop a cost-effective electrochemical environmental monitoring sensor and lipids for biofuel.

Covalent coupling to natural humic constituents comprises an important transformation pathway for anilinic pollutants in the environment. We systematically investigated the reactions of chlorine substituted anilines with catechol and syringic acid in horseradish peroxidase (HRP) catalyzed systems. It was demonstrated that although nucleophilic addition was the mechanism of covalent bonding to both catechol and syringic acid, chloroanilines coupled to the 2 humic constituents via slightly different pathways. 1,4-addition and 1,2-addition are involved to catechol and syringic acid, respectively. 1,4-addition showed empirical 2nd order kinetics and this pathway seemed to be more permanent than 1,2-addition. Stability experiments demonstrated that cross-coupling products with syringic acid could be easily released in acidic conditions. However, cross-coupling with catechol was relatively stable at similar conditions. Thus, the environmental behavior and bioavailability of the coupling products should be carefully assessed.

Hydrocarbons and their derivative compounds are recalcitrant in nature and causing adverse impacts to the environment and are classified as important pollutants. Removal of these pollutants from the atmosphere is a challenging process. Hydrophobic organic pollutants (HOPs) including crude oil, diesel, dotriacontane (C₃₂), and tetracontane (C₄₀) are subjected to the biodegradation study by using a bacterial consortium consist of Bacillus subtilis, Pseudomonas stutzeri, and Acinetobacter baumannii. The impact of pH and temperature on the biodegradation process was monitored. During the HOPs biodegradation, the impact of hydrocarbon-degrading extracellular enzymes such as alcohol dehydrogenase, alkane hydroxylase, and lipase was examined, and found average activity about 47.2, 44.3, and 51.8 μmol/mg⁻¹, respectively. Additionally, other enzymes such as catechol 1,2 dioxygenase and catechol 2,3 dioxygenase were found as 118 and 112 μmol/mg⁻¹ Enzyme as an average range in all the HOPs degradation, respectively. Also, the impact of the extracellular polymeric substance and proteins were elucidated during the biodegradation of HOPs with the average range of 116.90, 54.98 mg/L⁻¹ respectively. The impact of biosurfactants on the degradation of different types of HOPs is elucidated. Very slight changes in the pH were also noticed during the biodegradation study. Biodegradation efficiency was calculated as 90, 84, 76, and 72% for crude oil, diesel, C₃₂, and C₄₀, respectively. Changes in the major functional groups (CH, C–O–C, CO, =CH₂, CH₂, CH₃) were confirmed by FTIR analysis and intermediated metabolites were identified by GCMS analysis. The surface-active molecules along with the enzymes played a crucial role in the biodegradation process.

Bacterial degradation of crude oil in response to nutrient treatments has been vastly studied. But there is a paucity of information on kinetic parameters of crude oil degradation. Here we report the nutrient stimulated kinetic parameters of crude oil degradation assessed in terms of CO2 production and oil removal by Pseudomonas aeruginosa AKS1 and Bacillus sp. AKS2. The hydrocarbon degradation rate of P. aeruginosa AKS1 in oil only amended sediment was 10.75 ± 0.65 μg CO2-C g−1 sediment day−1 which was similar to degradation rate in sediments with no oil. In presence of both inorganic N & P, the degradation rate increased to 47.22 ± 1.32 μg CO2-C g−1 sediment day−1. The half-saturation constant (Ks) and maximum degradation rate (Vmax) for P. aeruginosa AKS1 under increasing N and saturating P concentration were 13.57 ± 0.53 μg N g−1 sediment and 39.36 ± 1.42 μg CO2-C g−1 sediment day−1 respectively. The corresponding values at increasing P and a constant N concentration were 1.60 ± 0.13 μg P g−1 sediment and 43.90 ± 1.03 μg CO2-C g−1 sediment day−1 respectively. Similarly the degradation rate of Bacillus sp. AKS2 in sediments amended with both inorganic nutrients N & P was seven fold higher than the rates in oil only or nutrient only treated sediments. The Ks and Vmax estimates of Bacillus sp. AKS2 under increasing N and saturating P concentration were 9.96 ± 1.25 μg N g−1 sediment and 59.96 ± 7.56 μg CO2-C g−1 sediment day−1 respectively. The corresponding values for P at saturating N concentration were 0.46 ± 0.24 μg P g−1 sediment and 63.63 ± 3.54 μg CO2-C g−1 sediment day−1 respectively. The rates of CO2 production by both isolates were further stimulated when oil concentration was increased above 12.5 mg g−1 sediment. However, oil degradation activity declined at oil concentration above 40 mg g−1 sediment when treated with constant nutrient: oil ratio. Both isolates exhibited alkane hydroxylase activity but aromatic degrading catechol 1, 2-dioxygenase and catechol 2, 3-dioxygenase activities were shown by P. aeruginosa AKS1 only.

Little is known about the effect of biochar on the degradation of paracetamol in soil, considering the ubiquity of this pollutant in the environment. Given the importance of the electrochemical properties of biochar for contaminant remediation, we investigated the influence of raw and designer redox-active biochars on paracetamol degradation in soil. Metabolite quantification indicated that a minimum of 53% of the spiked paracetamol was transformed in biochar-amended soil, resulting in the accumulation of different degradation products. The identification of these products allowed us to chart paracetamol degradation pathways in soil with and without biochar amendment. Some of the major degradation routes were observed to proceed via catechol and phenol, despite being previously described as having only a minor role in paracetamol metabolism. Additionally, a new transformation route from paracetamol to NAPQI was discovered in anaerobic soil originating from direct redox reactions on the surface of the designer biochars. These results may contribute to change our understanding of the environmental fate of paracetamol in soil and the role of biochar in its biodegradation.

Persulfate-based advanced oxidation process is considered as a promising technology for the degradation of phenol, where efficient, cost effective, and green methods with high peroxydisulfate (PS) activation capacity is of increasing demand. In this work, an in-situ liquid phase precipitation combined with ball milling method was applied for the synthesized of α-FeOOH/biochar, as be the PS activator for phenol degradation. Results showed that the ball-milled α-FeOOH and red pine wood biochar prepared at 700 °C (BM-α-FeOOH/PBC700) exhibited the highest catalytic property with PS for phenol oxidation (a phenol removal rate of 100%), compared with the BM-α-FeOOH (16.0%) and BMPBC700 (66.3%). The presence of intermediate products such as hydroquinone and catechol, and total organic carbon (TOC) removal rate (88.9%) proved the oxidation of phenol in the BM-α-FeOOH/PBC700+PS system. The characterization results showed that the functional groups (e.g., CO, C–O, Fe–O, and Si–O), the dissolved organic matter (DOM) in biochar, the loading of Fe element, and higher degree of graphitization and defect structures, contributed to the activation of PS to form free radicals (i.e., SO₄·⁻, ·OH, ·O₂⁻, and hVB⁺) for phenol oxidation, of which, SO₄·⁻ and ·OH account for 72.1% of the phenol removal rate. The specific contribution to the PS activation for phenol oxidation by each part of the materials was calculated based on the “whole to part” experiment. The contribution of DOM, acid-soluble substance, and carbon matrix and basal part in BM-α-FeOOH/PBC700 were 6.0%, 40.9%, and 53.1%, respectively. The reusability experiments of BM-α-FeOOH/PBC700 demonstrated that the composite was relatively stable after four cycles of reuse. Among three co-existing anions (NO₃⁻, Cl⁻, and HCO₃⁻), HCO₃⁻ played the most significant inhibition effects on phenol removal through reducing the phenol removal rate from 89.6% to 77.9%. This work provides guidance for the design of high active and stable carbon materials that activate PS to remove phenol.

Plant-endophyte synergism has been demonstrated to play a key role in the phytoremediation of contaminated water and soil. Phytoalexins, a type of chemical component in the plant apoplast, can be produced by plants in response to stimulation by endophytes. Phytoalexins may have distinct effects on the nutritional and metabolic functions of endophytes; however, direct evidence is not available to prove the effect of phytoalexins on the hydrophobic organic contaminants (HOC)-degradation activity of endophytes. In this paper, three different types of phytoalexins, coumarin, resveratrol and rutin, were selected to study their effect on the removal of polycyclic aromatic hydrocarbons (PAHs) by an endophytic bacterium Methylobacterium extorquens C1. The effects of the three phytoalexins on bacterial sorption and intracellular enzymatic activities were tested to further analyze the mechanism by which the phytoalexins affect the PAH degradation performance of M. extorquens C1. The results showed that the removal rate of PAHs by M. extorquens C1 increased in the presence of low levels of the three phytoalexins. The most effective concentrations of coumarin, resveratrol and rutin were 0.20, 0.15, and 0.25 mg/L, respectively, and the removal rate of PAHs was increased by approximately 18.3–35.0%. At the optimal concentrations, the three phytoalexins significantly promoted the sorption of PAHs by M. extorquens C1, and also enhanced the activities of catechol dioxygenases and dehydrogenase of M. extorquens C1. The positive effect of phytoalexins on both bacterial sorption and intracellular enzymatic activities promotes the overall removal of PAHs from endophytes. These results may deepen our understanding of plant-microbe cooperative mechanisms in the degradation of organic pollutants and provide a new approach for chemically enhanced bioremediation in the future.

The accumulation of phthalate acid esters (PAEs) in the environment has aroused a global concern. Microbial degradation is the most promising method for removing PAEs from polluted environment. Di-n-butyl phthalate (DBP) is one of the most widely used PAEs. In this study, a highly efficient DBP-degrading strain, Enterobacter sp. DNB-S2 was isolated from Mollisol in northeast China, and the degradation rate of 500 mg L⁻¹ DBP reached 44.10% at 5 °C and 91.08% at 50 °C within 7 days. A new intermediate, n-butyl benzoate BP, was detected, implying a new degradation pathway. The complete genome of the strain DNB-S2 was successfully sequenced to comprehensively understand of the entire DBP catabolic process. Key genes were proposed to be involved in DBP degradation, such as esterases, 3,4-dihydroxybenzoate decarboxylase and catechol 2,3-dioxygenase genes. Intermediate-utilization tests and real-time quantitative polymerase chain reaction (RT-qPCR) validated the proposed DBP catabolic pathway. The aboriginal bacterium DNB-S2 is a promising germplasm for restoring PAE-contaminated Mollisol regions at low temperature. This study provides novel insight into the catabolic mechanisms and abundant gene resources of PAE biodegradation.

Microbial community analysis of crude oil containing sludge collected from Duliajan oil field, Assam, India, showed the predominance of hydrocarbon-degrading bacteria such as Pseudomonas (20.1%), Pseudoxanthomonas (15.8%), Brevundimonas (1.6%), and Bacillus (0.8%) alongwith anaerobic, fermentative, nitrogen-fixing, nitrate-, sulfate-, and metal-reducing, syntrophic bacteria, and methanogenic archaea. Phylogenetic Investigation of Communities by Reconstruction of Unobserved States (PICRUSt) analysis indicated gene collection for potential hydrocarbon degradation, lipid, nitrogen, sulfur, and methane metabolism. The culturable microbial community was predominated by Pseudomonas and Bacillus with the metabolic potential for utilizing diverse hydrocarbons, crude oil, and actual petroleum sludge as sole carbon source during growth and tolerating various environmental stresses prevailing in such contaminated sites. More than 90% of the isolated strains could produce biosurfactant and exhibit catechol 2,3-dioxygenase activity. Nearly 30% of the isolates showed alkane hydroxylase activity with the maximum specific activity of 0.54 μmol min⁻¹ mg⁻¹. The study provided better insights into the microbial diversity and functional potential within the crude oil containing sludge which could be exploited for in situ bioremediation of contaminated sites.

This study reports on the feasibility of remediation of catechol- and resorcinol-contaminated water using low-cost sunflower seed hull activated carbon (SSHAC). Sunflower seed hull (SSH), an abundant agricultural waste in Malawi, was used as precursor to prepare highly porous activated carbon by physicochemical activation, with zinc chloride (ZnCl₂) as an activating agent. The activated carbon was characterized by FTIR, SEM-EDS, XRD and BET analyses. In this work, pertinent parameters that affect the adsorption efficiency—pH, initial adsorbate concentration, contact time, adsorbent dosage, and solution temperature—were investigated in batch mode. At the same experimental conditions, more catechol was adsorbed than resorcinol may be due to the compound’s affinity towards water and the position of the hydroxyl group on the benzene ring. A maximum equilibrium adsorption of 271 and 250 mg/g was obtained at pH 9.0 and pH 8.0 for catechol and resorcinol, respectively. The adsorption behaviour of both adsorbates (catechol and resorcinol) on SSHAC can be well described by Langmuir isotherm model and pseudo-second-order kinetic model. The value ∆G, ∆S and ∆H indicated spontaneous and endothermic adsorption process. The adsorption process was readily reversible allowing reusability of the adsorbate. This study’s outcome is value addition to this category of wastes for environmental protection.