Aromatic Intermediates Research Articles

Kinetic Modelling of Aromaticity and Colour Changes during the Degradation of Sulfamethoxazole Using Photo-Fenton Technology

Sulfamethoxazole (SMX) is an antibiotic that is extensively used in veterinary medicine, and its occurrence in wastewater and surface water can reach up to 20 μg/L. SMX is categorized as a pollutant of emerging concern by the US EPA due to its persistence and effects on humans and the environment. In this study, photo-Fenton technology is proposed for the removal of SMX. Aqueous solutions of SMX (50.0 mg/L) are treated in a 150 W UV photoreactor, using [Fe2+]0 = 0.5 mg/L and varying [H2O2]0 = 0–3.0 mM. During the reaction, colour (AU) was assessed along with SMX (mg/L), turbidity (NTU), and TC (mg/L). SMX degrades to aromatic intermediates with chromophoric groups, exhibiting colour (yellow to brown) and turbidity. As these intermediates are mineralized into CO2 and H2O, the colour and turbidity of the water lose intensity. Using a molar ratio of 1 mol SMX:10 mol H2O2, the maximum degradation of aromatic species takes place (71% elimination), and colourless water with turbidity < 1 NTU is obtained. A kinetic modelling for aromaticity loss and colour formation as a function of the oxidant concentration has been proposed. The application of this model allows the estimation of oxidant amounts for an efficient removal of SMX under environmentally friendly conditions.

Kinetic Study of the Water Quality Parameters during the Oxidation of Diclofenac by UV Photocatalytic Variants

Diclofenac (DCF, C14H11Cl2NO2) is a widely used non-steroidal anti-inflammatory drug, with a significant occurrence in waste effluents. DCF is especially persistent and difficult to degrade, with numerous toxic effects on aquatic fauna and humans. In 2015, DCF was identified as a priority pollutant (EU Directives on water policy). In this work, UV irradiation and its combination with hydrogen peroxide only or catalyzed by iron salts (photo-Fenton) are analyzed to find the most efficient alternative. DCF aqueous solutions were treated in a stirred 150 W UV photocatalytic reactor. Depending on the case, 1.0 mM H2O2 and 0–5.0 mg/L Fe2+ catalyst, such as FeSO4, was added. During the reaction, DCF, pH, turbidity, UVA at 254 and 455 nm, dissolved oxygen (DO), and TOC were assessed. The degradation of DCF yields a strong increase in aromaticity because of the rise in aromatic intermediates (mono-hydroxylated (4-hydroxy-diclofenac and 5-hydroxy-diclofenac) and di-hydroxylated products (4,5-dihydroxy-diclofenac), which subsequently generate compounds of a quinoid nature), which are very stable and non-degradable by UV light. Thus, only if H2O2 is added can UV completely degrade these aromatic colour intermediates. However, adding ferrous ion (photo-Fenton) the aromaticity remains constant due to iron com-plexes, that generates maximum colour and turbidity at an stoichiometric Fe2+ : DCF ratio of 3. As a result of the study, it is concluded that, with UV light only, a strong yellow colour is generated and maintained along the reaction, but by adding H2O2, a colourless appearance, low turbidity (<1 NTU), and [DO] = 8.1 mg/L are obtained. Surprisingly, photo-Fenton was found to be unsuitable for degrading DCF.

Drug-degrading bacteria isolated from the effluent water of a sewage plant.

Endocrine disruptors are potential environmental contaminants that can cause toxicity in aquatic ecosystems, so the Water Framework Directive has established limits for these compounds. During our research, 41 bacterial strains were isolated and identified from sewage effluent and tested for their degradation capacities for bisphenol A, 17β-estradiol, and nonylphenol. All the isolated bacteria belonged to the Gammaproteobacteria class of Pseudomonadota phylum (members of Citrobacter, Enterobacter, Escherichia, Klebsiella, Kluyvera, Leclercia, Raoultella, Shigella. Acinetobacter, Aeromonas, and Pseudomonas genera). During the experiments, only strains HF17, HF18 (Pseudomonas aeruginosa), and HF31 (Citrobacter freundii) were unable to grow on these compounds, all other bacterial strains could grow in the presence of the investigated endocrine disruptors. Based on the genomic analysis of the type strains, a set of genes involving aromatic compound degradation was detected, among the peripheral metabolic pathways, the quinate and benzoate degradation pathways proved to be widespread, among the central aromatic intermediates metabolism, the catechol branch of the beta-ketoadipate pathway was the most dominant. Pseudomonas fulva HF16 strain could utilize the investigated endocrine disruptors: bisphenol A by 34%, 17β-estradiol by 52%, and nonylphenol by 54%.

Pollution Characteristics and Ecological Impact of Screening Analysis of Fishing Port Sediments from Dalian, North China.

Environmental pollution from synthetic chemical mixtures has significant adverse impacts on marine ecosystems. However, identifying the main constituents of chemical mixtures that pose ecological threats is challenging due to the necessity of an integrated workflow for comprehensive identification and toxicological prioritization of pollutants. Here, an all-in-one mass spectrometric strategy integrating target, suspect, and nontarget analysis was used to investigate organic pollutants of concern in fishing port sediments, with 355 pollutants (32 from target analysis, 118 from suspect screening and 205 from nontarget analysis) identified in 11 categories. The chemical classes of polycyclic aromatic hydrocarbons (PAHs), pesticides, and intermediates were the extensively detected chemical classes. The ecological risks of absolutely quantified pollutants (i.e., 16 parent PAHs, 7 organophosphate esters (OPEs), 10 pesticides and 4 benzotriazole ultraviolet absorbers) were assessed using toxicity-weighted concentration ranking, with o,p'-DDT being the major contributor. Under the toxicological priority index (ToxPi) framework, an extended ranking of all identified pollutants was achieved by combining instrument response and detection frequency, with a priority control list of 15 pollutants obtained, of which benzo[ghi]perylene (BghiP) and p,p'-DDE had the highest risk priority. Due to frequent detection rates and significant environmental risks, routine monitoring of petroleum pollutants is considered essential. This study presents a general workflow that includes comprehensive identification and prioritization of pollutants, facilitating chemical management and ecological risk assessment.

Frequency-modulated alternating current-driven bioelectrodes for enhanced mineralization of Alizarin Yellow R

The alternating current (AC)-driven bioelectrochemical process, in-situ coupling cathodic reduction and anodic oxidation in a single electrode, offers a promising way for the mineralization of refractory aromatic pollutants (RAPs). Frequency modulation is vital for aligning reduction and oxidation phases in AC-driven bioelectrodes, potentially enhancing their capability to mineralize RAPs. Herein, a frequency-modulated AC-driven bioelectrode was developed to enhance RAP mineralization, exemplified by the degradation of Alizarin Yellow R (AYR). Optimal performance was achieved at a frequency of 1.67 mHz, resulting in the highest efficiency for AYR decolorization and subsequent mineralization of intermediates. Performance declined at both higher (3.33 and 8.30 mHz) and lower (0.83 mHz) frequencies. The bioelectrode exhibited superior electron utilization, bidirectional electron transfer, and redox bifunctionality, effectively aligning reduction and oxidation processes to enhance AYR mineralization. The 1.67 mHz frequency facilitated the assembly of a collaborative microbiome dedicated to AYR bio-mineralization, characterized by an increased abundance of functional consortia proficient in azo dye reduction (e.g., Stenotrophomonas and Shinella), aromatic intermediates oxidation (e.g., Sphingopyxis and Sphingomonas), and electron transfer (e.g., Geobacter and Pseudomonas). This study reveals the role of frequency modulation in AC-driven bioelectrodes for enhanced RAP mineralization, offering a novel and sustainable approach for treating RAP-bearing wastewater.

From 13C-lignin to 13C-mycelium: Agaricus bisporus uses polymeric lignin as a carbon source.

Plant biomass conversion by saprotrophic fungi plays a pivotal role in terrestrial carbon (C) cycling. The general consensus is that fungi metabolize carbohydrates, while lignin is only degraded and mineralized to CO2. Recent research, however, demonstrated fungal conversion of 13C-monoaromatic compounds into proteinogenic amino acids. To unambiguously prove that polymeric lignin is not merely degraded, but also metabolized, carefully isolated 13C-labeled lignin served as substrate for Agaricus bisporus, the world's most consumed mushroom. The fungus formed a dense mycelial network, secreted lignin-active enzymes, depolymerized, and removed lignin. With a lignin carbon use efficiency of 0.14 (g/g) and fungal biomass enrichment in 13C, we demonstrate that A. bisporus assimilated and further metabolized lignin when offered as C-source. Amino acids were high in 13C-enrichment, while fungal-derived carbohydrates, fatty acids, and ergosterol showed traces of 13C. These results hint at lignin conversion via aromatic ring-cleaved intermediates to central metabolites, underlining lignin's metabolic value for fungi.

Hydrogenolysis of Poly(Ethylene-co-Vinyl Alcohol) and Related Polymer Blends over Ruthenium Heterogeneous Catalysts.

The hydrogenolysis of polymers is emerging as a promising approach to deconstruct plastic waste into valuable chemicals. Yet, the complexity of plastic waste, including multilayer packaging, is a significant barrier to handling realistic waste streams. Herein, we reveal fundamental insights into a new chemical route for transforming a previously unaddressed fraction of plastic waste - poly(ethylene-co-vinyl alcohol) (EVOH) and related polymer blends - into alkane products. We report that Ru/ZrO2 is active for the concurrent hydrogenolysis, hydrogenation, and hydrodeoxygenation of EVOH and its thermal degradation products into alkanes (C1-C35) and water. Detailed reaction data, product analysis, and catalyst characterization reveal that the in-situ thermal degradation of EVOH forms aromatic intermediates that are detrimental to catalytic activity. Increased hydrogen pressure promotes hydrogenation of these aromatics, preventing catalyst deactivation and improving alkane product yields. Calculated apparent rates of C-C scission reveal that the hydrogenolysis of EVOH is slower than low-density polyethylene. We apply these findings to achieve hydrogenolysis of EVOH/polyethylene blends and elucidate the sensitivity of hydrogenolysis catalysts to such blends. Overall, we demonstrate progress towards efficient catalytic processes for the hydroconversion of waste multilayer film plastic packaging into valuable products.

Low temperature oxidation chemistry of n-butylbenzene in n-decane/n-butylbenzene mixture: Product characterization and kinetic modeling study

n-Alkanes and aromatics are two essential components in transportation fuels and have distinct oxidation reactivities. Due to products with different chemical functionalities generated in oxidation of n-alkanes and aromatics, the interaction kinetics may significantly affect the overall reactivity as well as product distributions. This work investigated the oxidation chemistry of the mixture of n-decane and n-butylbenzene, both of which are C10 hydrocarbons commonly used as jet fuel surrogate components. The experiments were conducted in a jet stirred reactor at pressure of 1 atm, the temperature range of 450–850 K, and the equivalence ratios of 0.5, 1.0 and 2.0. Key low temperature oxidation intermediates and radicals, including C10-cyclic ethers, C10-ketohydroperoxides, C10-ketodihydroperoxide, C10-diketohydroperoxide, benzyl hydroperoxide, methyl peroxy radical and methyl hydroperoxide, were detected by using synchrotron vacuum ultraviolet photoionization mass spectrometry. A detailed kinetic model was developed and validated against the speciation data in this work. Results reveal that the reactions of n-decane greatly enhance the low temperature oxidation reactivity of n-butylbenzene by efficiently producing reactive radicals, such as OH radicals. Besides, the reactions of n-butylbenzene play an inhibiting role in low temperature oxidation reactivity of n-decane. The measured intermediates, such as C10-cyclic ethers, C10-ketohydroperoxides and C10-ketodihydroperoxide, provide experimental evidence to validate the first, second and third O2-addition reactions, respectively. Due to the addition of n-decane, the evolution profiles of aromatic intermediates as a function of temperature are quite different from the cases of pure n-butylbenzene oxidation. For example, the formation of benzene, phenol and benzaldehyde at low temperatures is significantly enhanced, whose mole fractions present negative temperature coefficient behaviours. Finally, the reaction pathways of the binary fuel to produce C5C1 alkenes, alkynes, aldehydes, alcohols, acids and peroxides were analysed.

Catalytic hydroconversion of aryl ethers to polycyclic alkanes over Ni@MCM-41/β composite zeolite: Aromatic α-carbon activation and hydrogen transfer mechanisms

To produce high-density liquid fuels from lignite, a novel Ni-based bifunctional MCM-41/β composite zeolite (Ni@M/β) is reported for the catalytic hydroconversion (CHC) of lignite-derived aryl ethers to high-yield polycyclic alkanes (PCAs). Ni@M/β has a three-dimensional channel-type hierarchical porous texture with β as the core and MCM-41 as the shell. Stable Brønsted/Lewis acid sites and abundant internal/inter-zeolite defects also effectively promote the CHC of aryl ethers to PCAs. Under optimal conditions (5 MPa initial H2 pressure and 160 °C), selectivities of 2-(benzyloxy)naphthalene (BON) and benzyloxybenzene derived PCAs are as high as 76.0 and 90.5 %, respectively, with dimers and trimers dominating. DFT calculation based on electrostatic potential distribution on the van der Waals surface and Mulliken charge distribution of BON and derived oxygenated monomers shows that aromatic intermediates with >CaromaticOH have multiple accessible sites and are easy to bind with cation/radical fragments. Therefore, it is speculated that PCAs are mainly derived from C-C coupling induced by cation/radical fragments after the activation of aromatic α-carbon. In addition, the activation of H2 to H+, H·, δ+H···Hδ-, and H···H is mainly attributed to the strong Ni-M/β interaction and abundant defects. The whole CHC process is triggered mainly by the adsorption of H+ released by Ni@M/β at O sites of aryl ethers, and >Caliphatic-O- bridged bond cleavage is dominant. During this period, benzyl cation/radical produced by >C-O- bond cleavage and aromatic α-carbon activation (mainly) is coupled/reformed with adjacent aromatic fragments into corresponding polymers with non-oxygen bridged bonds, which are more easily converted to PCAs. This polycrystalline composite strategy improves the accessibility of large-sized molecules to active centers, and then increases the yields of PCAs, which is attractive for the clean and efficient conversion of lignite-derived oils to high-density liquid fuels.

Application of catalytic wet peroxide oxidation for sunscreen agents breakdown

Sunscreen agents are chemical compounds widely used nowadays for skin protection from UV sunlight. Recently, their ubiquitous occurrence in aquatic systems has been evidenced, which poses a high risk for the environment and human health as they are associated with endocrine disrupting activity, reproductive toxicity, and genotoxicity. In this work, the feasibility of an economically and environmentally friendly catalytic system based on the thermally modified natural magnetite and hydrogen peroxide (Fe3O4-R400/H2O2), has been evaluated for the degradation of two representative sunscreen agents: benzophenone-3 (BP-3) and 4-aminobenzoic acid (PABA) in wastewater. The experiments were conducted under circumneutral pH (pH0 = 5), with temperature control (25 °C). Both compounds (500 μg L−1) were successfully removed from water by using a relatively low catalyst concentration (0.5 g L−1) and the theoretical stoichiometric H2O2 dose for their complete oxidation (∼2.3 mg L−1). Afterwards, a complete operating condition study was performed with BP-3, given its predominant occurrence in fresh waters, analysing the influence of H2O2 dose (1.2–4.6 mg L−1), catalyst concentration (0.1–0.5 g L−1), and temperature (25–45 °C). From the evolution of the identified by-products, a reaction pathway was proposed according to which oxidation of BP-3 gives rise to several aromatic intermediates, which finally evolve to short-chain organic acids. The generation of such aromatic by-products led to a considerably ecotoxicity increase in the initial stages of the reaction, but non-toxic effluents were ultimately achieved. Notably, the mineralization yield reached was above 60%. As a proof of concept, the feasibility of the system was finally demonstrated in real water matrices (WWTP effluent and surface water).

INVESTIGATION OF THE TRANSFORMATION OF MODEL PETROLEUM RAW MATERIALS UNDER CRACKING CONDITIONS OVER A REGENERATED SPENT HYDROTREATMENT CATALYST

The physicochemical properties and catalytic activity of regenerated spent aluminium-cobalt-molybdenum hydrotreatment catalyst have been investigated under cracking conditions in the model systems n-dodecane - toluene and decalin - toluene - n-hexane. A series of experiments to study the catalytic activity of the sample was carried out using a flow-type laboratory installation within the temperature range 430-470 °C, nitrogen pressure 1.6 MPa, liquid hourly space velocity 0.5-3.0 h-1. The directions of transformation were determined for paraffin and naphthenic hydrocarbons by means of gas chromatography - mass spectrometry. Paraffin hydrocarbons enter into cracking, isomerisation and compaction reactions. Naphthenic hydrocarbons are transformed into the products of isomerisation, dehydrogenation and compaction. Predominant dehydrogenation of decalin with the formation of naphthalene and hydrogen is observed in the system under investigation. A positive role of hydrogen in thermodestructive processing of heavy oil residues is observed due to the hydrogenation of nonlinear olefin hydrocarbons and aromatic hydrocarbon intermediates, which decreases the rate of coke formation. The corresponding reaction rate constants were calculated, and the results were analysed. Conclusions are drawn about the prospects of introducing a regenerated spent hydrotreatment catalyst into the procedure of thermodestructive processing of heavy oil residues.

Revealing the low to moderate temperature oxidation kinetics of 1,2,4-trimethylbenzene sensitized by dimethyl ether

Low to moderate temperature oxidation has been a vital topic in the combustion chemistry due to its critical role in controlling the combustion characteristics such as autoignition and pollutant emissions. Low temperature oxidation kinetics of alkanes and oxygenated biofuels have been widely explored, while that of branched aromatics is poorly understood. This work aims to investigate the low to moderate temperature oxidation kinetics of 1,2,4-trimethylbenzene (TMB, C9H12), which is a multi-branched alkylbenzene with weak low temperature oxidation reactivity. To enhance the low temperature oxidation reactivity of TMB, dimethyl ether (DME) was added to efficiently provide chain initiators. The oxidation experiment of TMB/DME mixture was performed with an atmospheric jet stirred reactor coupled with synchrotron vacuum ultraviolet radiation photoionization mass spectrometry. The negative temperature coefficient (NTC) behavior, as well as featured aromatic intermediates, especially phenyl hydroperoxides and unexpected highly oxygenated molecules (HOMs), were observed in the experiment. The detection of these fingerprint aromatic intermediates provide crucial evidence for revealing the low to moderate oxidation kinetics of TMB. In addition, a kinetic model was developed to provide in-depth kinetic analysis. The results demonstrate that the active chain initiators produced from DME oxidation trigger the low temperature chain-branching reactions of TMB. The chain recycling process is further sustained due to the regeneration of active intermediates such as phenyl hydroperoxides and •OH radicals. Aromatic intermediates with chemical compositions of C9H12Ox and C9H10Ox were measured and identified to be key indicators for the low temperature chemistry of TMB. In particular, the aromatic HOMs (C9H12O6 and C9H10O5) are fingerprint intermediates produced from the third O2 addition and subsequent reactions of TMB. Besides, the sensitivity analysis indicates that the interaction kinetics between TMB and DME by sharing the highly sensitive reactions of hydroperoxides and •OH radicals. The present work extends the conceptual reaction schemes proposed in alkanes towards branched aromatics, especially sequential O2 addition reactions that contributing to the formation of phenyl hydroperoxides and HOMs.

Metagenomic analysis reveals the distribution, function, and bacterial hosts of degradation genes in activated sludge from industrial wastewater treatment plants

For comprehensive insights into the bacterial community and its functions during industrial wastewater treatment, with a particular emphasis on its pivotal role in the bioremediation of organic pollutants, this study utilized municipal samples as a control group for metagenomic analysis. This approach allowed us to investigate the distribution, function, and bacterial hosts of biodegradation genes (BDGs) and organic degradation genes (ODGs), as well as the dynamics of bacterial communities during the industrial wastewater bioprocess. The results revealed that BDGs and ODGs associated with the degradation of benzoates, biphenyls, triazines, nitrotoluenes, and chlorinated aromatics were notably more abundant in the industrial samples. Specially, genes like clcD, linC, catE, pcaD, hbaB, hcrC, and badK, involved in the peripheral pathways for the catabolism of aromatic compounds, benzoate transport, and central aromatic intermediates, showed a significantly higher abundance of industrial activated sludge (AS) than municipal AS. Additionally, the BDG/ODG co-occurrence contigs in industrial samples exhibited a higher diversity in terms of degradation gene carrying capacity. Functional analysis of Clusters of Orthologous Groups (COGs) indicated that the primary function of bacterial communities in industrial AS was associated with the category of “metabolism”. Furthermore, the presence of organic pollutants in industrial wastewater induced alterations in the bacterial community, particularly impacting the abundance of key hosts harboring BDGs and ODGs (e.g. Bradyrhizobium, Hydrogenophaga, and Mesorhizobium). The specific hosts of BDG/ODG could explain the distribution characteristics of degradation genes. For example, the prevalence of the Adh1 gene, primarily associated with Mesorhizobium, was notably more prevalent in the industrial AS. Overall, this study provides valuable insights into the development of more effective strategies for the industrial wastewater treatment and the mitigation of organic pollutant contamination.

An Overview on Production of Lignocellulose-Derived Platform Chemicals Such as 5-Hydroxymethyl Furfural, Furfural, Protocatechuic Acid

Furan derivatives such as 5-hydroxymethyl furfural (HMF) and furfural (FA) and aromatic acids such as protocatechuic acid (PCA) represent the most essential classes of intermediates derived from lignocellulosic biomass. These bio-based compounds are potential feedstocks for producing bio-based chemicals and fuels. However, the derivatives of these bio-based compounds are useful in their antioxidative, antibacterial, and anti-aging activities. Protocatechuic acid (PCA, 2,3-dihydroxybenzoic acid), derived from lignin biomass, is also one of the essential bio-derived aromatic intermediates with an active acid and hydroxyl group, which can elevate it into an important class of potential platform chemicals for the production of value-added chemicals, such as HMF and furfuryl alcohol (FAL). The platform compounds are indeed the most used furan-based feedstocks since their chemical structure allows the preparation of various high-value-added chemicals. The related catalytic techniques are well known for the upgradation of biomass into these platform chemicals and their conversion into value-added chemicals. In this short review, we aim to briefly discuss biomass conversion into FA, HMF, and PCA and related heterogeneous catalytic processes. In addition, a few potential ongoing research trends are also proposed to provide some ideas for the further preparation of bio-based innovative derivatives in a much more green, simple, efficient, and economical way.

Insights into antibiotic cefaclor mineralization by electro-Fenton and photoelectro-Fenton processes using a Ti/Ti4O7 anode: Performance, mechanism, and toxic chlorate/perchlorate formation

A comparative degradation of antibiotic cefaclor (CEC) between Ti/Ti4O7 and Ti/RuO2 anodes, in terms of degradation kinetics, mineralization efficiency, and formation of toxic chlorate (ClO3−) and perchlorate (ClO4−), was performed with electrochemical-oxidation (EO), electro-Fenton (EF), and photoelectro-Fenton (PEF) processes. Besides, CEC degradation by EF with boron-doped diamond (BDD) anode was also tested. Results showed CEC decays always followed pseudo-first-order kinetics, with increasing apparent rate constants in the sequence of EO < EF < PEF. The mineralization efficiency of the processes with Ti/Ti4O7 anode was higher than that of Ti/RuO2 anode, but slightly lower than that of BDD anode. Under the optimal conditions, 94.8% mineralization was obtained in Ti/Ti4O7-PEF, which was much higher than 64.4% in Ti/RuO2-PEF. The use of Ti/RuO2 gave no generation of ClO3− or ClO4−, while the use of Ti/Ti4O7 yielded a small amount of ClO3− and trace amounts of ClO4−. Conversely, the use of BDD led to the highest generation of ClO3− and ClO4−. The reaction mechanism was studied systematically by detecting the generated H2O2 and •OH. The initial N of CEC was released as NH4+ and, in smaller proportion, as NO3−. Four short-chain carboxylic acids and nine aromatic intermediates were also detected, a possible reaction sequence for CEC mineralization was finally proposed.

Simultaneous carbon catabolite repression governs sugar and aromatic co-utilization in Pseudomonas putida M2.

Pseudomonas putida have emerged as promising biocatalysts for the conversion of sugars and aromatic compounds obtained from lignocellulosic biomass. Understanding the role of carbon catabolite repression (CCR) in these strains is critical to optimize biomass conversion to fuels and chemicals. The CCR functioning in P. putida M2, a strain capable of consuming both hexose and pentose sugars as well as aromatic compounds, was investigated by cultivation experiments, proteomics, and CRISPRi-based gene repression. Strain M2 co-utilized sugars and aromatic compounds simultaneously; however, during cultivation with glucose and aromatic compounds (p-coumarate and ferulate) mixture, intermediates (4-hydroxybenzoate and vanillate) accumulated, and substrate consumption was incomplete. In contrast, xylose-aromatic consumption resulted in transient intermediate accumulation and complete aromatic consumption, while xylose was incompletely consumed. Proteomics analysis revealed that glucose exerted stronger repression than xylose on the aromatic catabolic proteins. Key glucose (Eda) and xylose (XylX) catabolic proteins were also identified at lower abundance during cultivation with aromatic compounds implying simultaneous catabolite repression by sugars and aromatic compounds. Reduction of crc expression via CRISPRi led to faster growth and glucose and p-coumarate uptake in the CRISPRi strains compared to the control, while no difference was observed on xylose+p-coumarate. The increased abundances of Eda and amino acid biosynthesis proteins in the CRISPRi strain further supported these observations. Lastly, small RNAs (sRNAs) sequencing results showed that CrcY and CrcZ homologues levels in M2, previously identified in P. putida strains, were lower under strong CCR (glucose+p-coumarate) condition compared to when repression was absent (p-coumarate or glucose only). IMPORTANCE A newly isolated Pseudomonas putida strain, P. putida M2, can utilize both hexose and pentose sugars as well as aromatic compounds making it a promising host for the valorization of lignocellulosic biomass. Pseudomonads have developed a regulatory strategy, carbon catabolite repression, to control the assimilation of carbon sources in the environment. Carbon catabolite repression may impede the simultaneous and complete metabolism of sugars and aromatic compounds present in lignocellulosic biomass and hinder the development of an efficient industrial biocatalyst. This study provides insight into the cellular physiology and proteome during mixed-substrate utilization in P. putida M2. The phenotypic and proteomics results demonstrated simultaneous catabolite repression in the sugar-aromatic mixtures, while the CRISPRi and sRNA sequencing demonstrated the potential role of the crc gene and small RNAs in carbon catabolite repression.

Pyridine-bridged cobalt tetra-aminophthalocyanine to active peroxymonosulphate for efficient degrading carbamazepine

ABSTRACT In this study, each cobalt tetra-aminophthalocyanine (CoTAPc) molecule was immobilised with four isonicotinic acid (INA) molecules by amide bonding, a novel and highly efficient catalyst pyridine-bridged cobalt tetra-aminophthalocyanine (CoTAPc-TINA) was synthesised. The introduction of INA molecules promoted CoTAPc to expose more active sites, and increased the electron cloud density of cobalt ions promoting O–O bond homolysis of PMS to generate more active species, which significantly enhanced catalytic activity. With the pharmaceutical of carbamazepine (CBZ) as model pollutant, 0.1 g/L CoTAPc-TINA in dark in the presence of 0.4 mM PMS, 98.8% CBZ was removed within 10 min. However, under the same conditions the removed of CBZ was only 58.9% by CoTAPc/PMS system. Radical capture experiments combined electron paramagnetic resonance technology demonstrate that hydroxyl radicals, sulphate radicals, superoxide radicals and singlet oxygen are the main active species in the CoTAPc-TINA/PMS system. As the reaction proceeded, all aromatic intermediates were transformed to small molecular acids by these active species. This investigation provided a new insight for application of metal phthalocyanine in wastewater treatment.

Degradation of levofloxacin from antibiotic wastewater by pulse electrochemical oxidation with BDD electrode

Antibiotic-containing wastewater is a typical biochemical refractory organic wastewater and general treatment methods cannot effectively and quickly degrade the antibiotic molecules. In this study, a novel boron-doped diamond (BDD) pulse electrochemical oxidation (PEO) technology was proposed for the efficient removal of levofloxacin (LFXN) from wastewater. The effects of current density (j), initial pH (pH0), frequency (f), electrolyte types and initial concentration (c0(LFXN)) on the degradation of LFXN were systematically investigated. The degradation kinetics under four different processes have also been studied. The possible degradation mechanism of LFXN was proposed by Density functional theory calculation and analysis of degradation intermediates. The results showed that under the optimal parameters, the COD removal efficiency (η(COD)) was 94.4% and the energy consumption (EEC) was 81.43 kWh·m−3 at t = 120 min. The degradation of LFXN at pH = 2.8/c(H2O2) followed pseudo-first-order kinetics. The apparent rate constant was 1.33 × 10−2 min−1, which was much higher than other processes. The degradation rate of LFXN was as follows: pH = 2.8/c(H2O2) > pH = 2.8 > pH = 7/c(H2O2) > pH = 7. Ten aromatic intermediates were formed during the degradation of LFXN, which were further degraded to F−, NH4+, NO3−, CO2 and H2O. This study provides a promising approach for efficiently treating LFXN antibiotic wastewater by pulsed electrochemical oxidation with a BDD electrode without adding H2O2.

Assessment of photo electro-Fenton and solar photo electro-Fenton processes for the efficient degradation of asulam herbicide

The degradation of asulam herbicide by photo electro-Fenton (PEF) and solar photo electro-Fenton (SPEF) processes was studied using an undivided electrochemical BDD/carbon-felt cell to generate H2O2 continuously. A central composite design combined with response surface methodology was applied to determine the optimal operating conditions of current intensity = 0.30 A, [Fe2+] = 0.3 mM, and [Na2SO4] = 0.11 M at pH 3 to achieve the complete degradation of asulam by electro-Fenton. Subsequently, the SPEF process was more efficient treatment compared to PEF, achieving a complete degradation of asulam and 98% of mineralization in 180 min. Moreover, 4-aminobenzenesulfonamide, 4-aminophenol, and 4-benzoquinone were detected as aromatic intermediates, whereas acetic acid, oxalic acid, and NO3− ions were identified as final degradation by-products. Thus, the SPEF process is an efficient alternative for the complete degradation and mineralization of herbicide asulam in an aqueous solution under natural sunlight.

Characterization of a novel aromatic substrate-processing microcompartment in Actinobacteria.

We have discovered a new cluster of genes that is found exclusively in the Actinobacteria phylum. This locus includes genes for the 2-aminophenol meta-cleavage pathway and the shell proteins of a bacterial microcompartment (BMC) and has been named aromatics (ARO) for its putative role in the breakdown of aromatic compounds. In this study, we provide details about the distribution and composition of the ARO BMC locus and conduct phylogenetic, structural, and functional analyses of the first two enzymes in the catabolic pathway: a unique 2-aminophenol dioxygenase, which is exclusively found alongside BMC shell genes in Actinobacteria, and a semialdehyde dehydrogenase, which works downstream of the dioxygenase. Genomic analysis reveals variations in the complexity of the ARO loci across different orders. Some loci are simple, containing shell proteins and enzymes for the initial steps of the catabolic pathway, while others are extensive, encompassing all the necessary genes for the complete breakdown of 2-aminophenol into pyruvate and acetyl-CoA. Furthermore, our analysis uncovers two subtypes of ARO BMC that likely degrade either 2-aminophenol or catechol, depending on the presence of a pathway-specific gene within the ARO locus. The precise precursor of 2-aminophenol, which serves as the initial substrate and/or inducer for the ARO pathway, remains unknown, as our model organism Micromonospora rosaria cannot utilize 2-aminophenol as its sole energy source. However, using enzymatic assays, we demonstrate the dioxygenase's ability to cleave both 2-aminophenol and catechol in vitro, in collaboration with the aldehyde dehydrogenase, to facilitate the rapid conversion of these unstable and toxic intermediates. IMPORTANCE Bacterial microcompartments (BMCs) are proteinaceous organelles that are widespread among bacteria and provide a competitive advantage in specific environmental niches. Studies have shown that the genetic information necessary to form functional BMCs is encoded in loci that contain genes encoding shell proteins and the enzymatic core. This allows the bioinformatic discovery of BMCs with novel functions and expands our understanding of the metabolic diversity of BMCs. ARO loci, found only in Actinobacteria, contain genes encoding for phylogenetically remote shell proteins and homologs of the meta-cleavage degradation pathway enzymes that were shown to convert central aromatic intermediates into pyruvate and acetyl-CoA in gamma Proteobacteria. By analyzing the gene composition of ARO BMC loci and characterizing two core enzymes phylogenetically, structurally, and functionally, we provide an initial functional characterization of the ARO BMC, the most unusual BMC identified to date, distinctive among the repertoire of studied BMCs.