Large-scale enzymatic membrane reactors for tetracycline degradation in WWTP effluents

Enzymatic degradability of diclofenac ozonation products: A mechanistic analysis

The treatment of waterborne micropollutants, such as diclofenac, presents a significant challenge to wastewater treatment plants due to their incomplete removal by conventional methods. Ozonation is an effective technique for the degradation of micropollutants. However, incomplete oxidation can lead to the formation of ecotoxic by-products that require a subsequent post-treatment step. In this study, we analyze the susceptibility of micropollutant ozonation products to enzymatic digestion with laccase from Trametes versicolor to evaluate the potential of enzymatic treatment as a post-ozonation step. The omnipresent micropollutant diclofenac is used as an example, and the enzymatic degradation kinetics of all 14 detected ozonation products are analyzed by high-performance liquid chromatography coupled with high-resolution mass spectrometry (HPLC-HRMS) and tandem mass spectrometry (MS2). The analysis shows that most of the ozonation products are responsive to chemo-enzymatic treatment but show considerable variation in enzymatic degradation kinetics and efficiencies. Mechanistic investigation of representative transformation products reveals that the hydroxylated aromatic nature of the ozonation products matches the substrate spectrum, facilitating their rapid recognition as substrates by laccase. However, after initiation by laccase, the subsequent chemical pathway of the enzymatically formed radicals determines the global degradability observed in the enzymatic process. Substrates capable of forming stable molecular oxidation products inhibit complete detoxification by oligomerization. This emphasizes that it is not the enzymatic uptake of the substrates but the channelling of the reaction of the substrate radicals towards the oligomerization of the substrate radicals that is the key step in the further development of an enzymatic treatment step for wastewater applications.

Research progress on the origin, fate, impacts and harm of microplastics and antibiotic resistance genes in wastewater treatment plants

Previous studies reported microplastics (MPs), antibiotics, and antibiotic resistance genes (ARGs) in wastewater treatment plants (WWTPs). There is still a lack of research progress on the origin, fate, impact and hazards of MPs and ARGs in WWTPs. This paper fills a gap in this regard. In our search, we used "microplastics", "antibiotic resistance genes", and "wastewater treatment plant" as topic terms in Web of Science, checking the returned results for relevance by examining paper titles and abstracts. This study mainly explores the following points: (1) the origins and fate of MPs, antibiotics and ARGs in WWTPs; (2) the mechanisms of action of MPs, antibiotics and ARGs in sludge biochemical pools; (3) the impacts of MPs in WWTPs and the spread of ARGs; (4) and the harm inflicted by MPs and ARGs on the environment and human body. Contaminants in sewage sludge such as MPs, ARGs, and antibiotic-resistant bacteria enter the soil and water. Contaminants can travel through the food chain and thus reach humans, leading to increased illness, hospitalization, and even mortality. This study will enhance our understanding of the mechanisms of action among MPs, antibiotics, ARGs, and the harm they inflict on the human body.

Co2+-adsorbed chitosan-grafted-poly(acrylic acid) hydrogel as peroxymonosulfate activator for effective dye degradation

In this work, chitosan-grafted-poly(acrylic acid) (CS-g-PAA) was synthesized for use as a Co2+ adsorbent and circularly utilized as a peroxymonosulfate (PMS) activator in the degradation of rhodamine B (RhB) dye. CS-g-PAA demonstrated 3.7 times higher adsorption capacity toward Co2+ than pristine chitosan. The impact of the adsorption conditions was evaluated. The pseudo-second-order kinetic model and the Langmuir isotherm model best described the adsorption process. Under optimum conditions, the adsorption capacity of CS-g-PAA for Co2+ was 212 mg/g. The Co2+-adsorbed CS-g-PAA hydrogel was further utilized in the RhB degradation process. The effects of catalyst dosage, initial RhB concentration, pH, and the coexistence of anions on the degradation of RhB were studied. The hydrogel catalyst could remove 98 % of RhB within 5 min, at a degradation rate of 0.624 per min. Electron paramagnetic resonance (EPR) analysis and the radical scavenger experiment suggested that SO4•-, HO•, 1O2, and O2•- were involved in the degradation. Furthermore, when tested in various water systems, high degradation efficiencies of 98 % were attained after 20 min. The hydrogel catalyst performed excellent degradation over ten cycles without any chemical recovery processes. Moreover, high degradation efficiencies were observed between 95 % and 98 % when tested with other dyes.

Bimetal doped Cu-Fe-ZIF-8/g-C3N4 nanocomposites for the adsorption of tetracycline hydrochloride from water

Bimetal doped Cu-Fe-zeolitic imidazole framework-8 (ZIF-8)/graphitic carbon nitride (GCN) (Cu-Fe-ZIF-8/GCN) nanocomposites were prepared via one-pot and ion-exchange methods. The main influencing factors, such as adsorbent concentration, TC concentration, initial pH, and coexisting ions, were evaluated in detail. Due to the suitable pore structures and the presence of multiple interactions on the surface, the nanocomposite showed a high adsorption capacity up to 932 mg g-1 for tetracycline hydrochloride (TC), outperforming ZIF-8 by 4.8 times. The adsorption kinetics and adsorption isotherm were depicted in good detail using pseudo-second-order kinetic and Langmuir models, respectively. Thermodynamic calculation revealed that the adsorption of the nanocomposite under experimental conditions was a spontaneous heat absorption process, and was primarily driven by chemisorption. After four cycles of use, the nanocomposite retained 87.2% of its initial adsorption capacity, confirming its high reusability and broad application prospects in removing tetracycline-type pollutants from wastewater.

Enzymatic degradation of tetracycline by Trametes versicolor laccase in a fluidized bed reactor

Laccase from Trametes Versicolor was successfully immobilized on gelatin beads by a crosslinking reaction with glutaraldehyde. Immobilized laccases showed better stability towards pH and temperature than free laccases. Moreover, the immobilized laccases retained a good relative activity of 85 % after 20 days of storage at 4 °C. The degradation of tetracycline (TC) was studied with immobilized enzymes in both batch and fluidized bed reactors (FBR). The average degradation rate (1.59 mg h-1 Uenzymes-1) estimated over 24 h in the FBR was almost 5 times higher than in the stirred tank reactor. Maximum degradation rate achieved was 72 ± 1 % with a circulation flow rate of 80 mL min-1 and addition of air at a flowrate of 15 mL min-1. Study of the stability of the active beads under reaction conditions, shows that 45 % of the TC was degraded after 5 cycles of 24 h each. The toxicity of the TC solution before and after treatment was also investigated with microtox assays.

Chitosan-grafted hydrogels for heavy metal ion adsorption and catalytic reduction of nitroaromatic pollutants and dyes

Chitosan-grafted-poly(acrylic acid) (CS-g-PAA) and chitosan-grafted- poly(2-acrylamido-2-methyl-1-propanesulfonic acid) (CS-g-P(AA-co-AMPS)) hydrogels were synthesized and then employed as adsorbents for the effective removal of Cu2+ and other heavy metal ions. The effect of hydrogel's composition on the Cu2+ adsorption was explored. The CS-g-PAA hydrogel demonstrated a superior adsorption capacity compared to pristine CS, PAA hydrogel, and CS-g-P(AA-co-AMPS) hydrogels. The adsorption followed the Langmuir isotherm model, and the pseudo-second order kinetic model. Additionally, the CS-g-PAA hydrogel exhibited relatively high adsorption performances toward Cr3+, Co2+, Ni2+, Pb2+, and Zn2+. Metal ions adsorbed within CS-g-PAA hydrogels underwent reduction to their corresponding metallic states and were reutilized as catalysts for the reduction of 4-nitrophenol. The comparative catalytic performances of the metal species in the hydrogel were in the order of Cu > Ni > Co > Zn. The reduction efficiency of Cu-CS-g-PAA increased with increased catalyst dosage, NaBH4 concentration, and temperature. A very low activation energy of 3.7 kJ/mol was observed. The catalyst maintained high catalytic performance even when subjected to real water samples and proved its reusability for up to three cycles. Moreover, the catalyst could effectively reduce 2-nitrophenol and methyl orange.

Poly(acrylic acid-co-2-acrylamido-2-methyl-1-propanesulfonic acid)-grafted chitosan hydrogels for effective adsorption and photocatalytic degradation of dyes

As a result of the growth of industrialization and urbanization, the water ecosystem is contaminated by various pollutants, including heavy metal ions and dyes. The use of low-cost and environmentally friendly dye adsorbents has been investigated. A hydrogel was fabricated via graft polymerization of acrylic acid (AA) and 2-acrylamido-2-methyl-1-propanesulfonic acid (AMPS) onto chitosan. The hydrogel was used as a dye adsorbent and support for a zinc oxide (ZnO) powder photocatalyst. The adsorption capacity of the bare hydrogel was greater towards cationic dyes than anionic dyes. Grafting P(AA-co-AMPS) exhibited a 23-time increase in adsorption capacity towards crystal violet (CV) compared to pristine chitosan. The effect of the AA-AMPS molar ratio on CV adsorption was studied. A hydrogel with an AA-AMPS ratio of 10 : 1 had the highest adsorption capacity towards CV in water, removing 91% of the dye in 12 h. The maximum adsorption capacity was 2023 mg g-1. The adsorption kinetics and isotherm were described by the pseudo-second-order model and the Langmuir model, respectively. ZnO particles were in situ synthesized within the 10 : 1 hydrogel to facilitate the recovery of the photocatalyst. The ZnO hydrogel composite could remove 95% and 92% of CV from solutions on the 1st and 2nd cycle, respectively. In addition, the hydrogel composite containing only 8.7 wt% of ZnO particles effectively degraded adsorbed CV under sunlight and could be reused without requiring a chemical regeneration or photocatalyst recovery procedure. This hydrogel composite is an effective dual-functional material for the adsorption and photodegradation of dye pollutants in wastewater.

Degradation of tetracycline by activated peroxodisulfate using a sulfur-modified iron-based material

The activation of persulfate by an iron-based catalyst presents a promising approach for the degradation of antibiotics; however, the activation efficiency remains a challenge. Herein, a sulfur-modified iron-based catalyst (S-Fe) by co-precipitation of sodium thiosulfate and ferrous sulfate in a molar ratio of 1:2 was prepared and the efficacy of the S-Fe/PDS system for the removal of tetracycline (TCH) was studied, where a higher removal efficiency was observed compared to the Fe/PDS system. Moreover, the effects of TCH concentration, PDS concentration, initial pH, and catalyst dosage on TCH removal were evaluated, and the highest efficiency was about 92.6% within a 30 min reaction time using a catalyst dosage of 1.0 g/L, a PDS dosage of 2.0 g/L, and a solution pH value of 7. The products and degradation pathways of TCH were analyzed by LC-MS. The free-radical-quenching experiments revealed that both SO₄^- • and •OH radicals contributed to the degradation of TCH in the S-Fe/PDS system, with the former playing a more significant role. The S-Fe catalyst also showed good stability and reusability for the removal of organic pollutants. Our findings suggest that the modification of an iron-based catalyst offers an effective approach to activate persulfate for removal of tetracycline antibiotics.

Enzymatic post-treatment of ozonation: laccase-mediated removal of the by-products of acetaminophen ozonation

Ozonation is a powerful technique to remove micropollutants from wastewater. As chemical oxidation of wastewater comes with the formation of varying, possibly persistent and toxic by-products, post-treatment of the ozonated effluent is routinely suggested. This study explored an enzymatic treatment of ozonation products using the laccase from Trametes versicolor. A high-performance liquid chromatography coupled with high-resolution mass spectrometry (HPLC-HRMS) analysis revealed that the major by-products were effectively degraded by the enzymatic post-treatment. The enzymatic removal of the by-products reduced the ecotoxicity of the ozonation effluent, as monitored by the inhibition of Aliivibrio fischeri. The ecotoxicity was more effectively reduced by enzymatic post-oxidation at pH 7 than at the activity maximum of the laccase at pH 5. A mechanistic HPLC-HRMS and UV/Vis spectroscopic analysis revealed that acidic conditions favored rapid conversion of the phenolic by-products to dead-end products in the absence of nucleophiles. In contrast, the polymerization to harmless insoluble polymers was favored at neutral conditions. Hence, coupling ozonation with laccase-catalyzed post-oxidation at neutral conditions, which are present in wastewater effluents, is suggested as a new resource-efficient method to remove persistent micropollutants while excluding the emission of potentially harmful by-products.

Current Challenges for Biological Treatment of Pharmaceutical-Based Contaminants with Oxidoreductase Enzymes: Immobilization Processes, Real Aqueous Matrices and Hybrid Techniques

The worldwide access to pharmaceuticals and their continuous release into the environment have raised a serious global concern. Pharmaceuticals remain active even at low concentrations, therefore their occurrence in waterbodies may lead to successive deterioration of water quality with adverse impacts on the ecosystem and human health. To address this challenge, there is currently an evolving trend toward the search for effective methods to ensure efficient purification of both drinking water and wastewater. Biocatalytic transformation of pharmaceuticals using oxidoreductase enzymes, such as peroxidase and laccase, is a promising environmentally friendly solution for water treatment, where fungal species have been used as preferred producers due to their ligninolytic enzymatic systems. Enzyme-catalyzed degradation can transform micropollutants into more bioavailable or even innocuous products. Enzyme immobilization on a carrier generally increases its stability and catalytic performance, allowing its reuse, being a promising approach to ensure applicability to an industrial scale process. Moreover, coupling biocatalytic processes to other treatment technologies have been revealed to be an effective approach to achieve the complete removal of pharmaceuticals. This review updates the state-of-the-art of the application of oxidoreductases enzymes, namely laccase, to degrade pharmaceuticals from spiked water and real wastewater. Moreover, the advances concerning the techniques used for enzyme immobilization, the operation in bioreactors, the use of redox mediators, the application of hybrid techniques, as well as the discussion of transformation mechanisms and ending toxicity, are addressed.

Experimental and modeling of tetracycline degradation in water in a flow-through enzymatic monolithic reactor

In this work, the laccase from Trametes versicolor was immobilized in highly porous silica monoliths (0.6-cm diameter, 0.5-cm length). These monoliths feature a unique homogeneous network of interconnected macropores (20 μm) with mesopores (20 nm) in the skeleton and a high specific surface area (330 m²/g). The enzymatic monoliths were applied to degrade tetracycline (TC) in model aqueous solutions (20 ppm). For this purpose, a tubular flow-through reactor (FTR) configuration with recycling was built. The TC degradation was improved with oxygen saturation, presence of degradation products, and recirculation rate. The TC depletion reaches 50% in the FTR and 90% in a stirred tank reactor (CSTR) using crushed monoliths. These results indicate the importance of maintaining a high co-substrate concentration near active sites. A model coupling mass transfers with a Michaelis-Menten kinetics was applied to simulate the TC degradation in real wastewaters at actual TC concentration (2.8 10^-4 ppm). Simulation results show that industrial scale FTR reactor should be suitable to degrade 90% of TC in 5 h at a flow rate of 1 mL/min in a single passage flow configuration. Nevertheless, the process could certainly be further optimized in terms of laccase activity, oxygen supply near active sites, and contact time.

Perylene diimide supermolecule (PDI) as a novel and highly efficient cocatalyst for photocatalytic degradation of tetracycline in water: A case study of PDI decorated graphitic carbon nitride/bismuth tungstate composite

Employing perylene diimide supermolecule (PDI) as metal-free cocatalyst, a novel PDI/g-C₃N₄/Bi₂WO₆ (PCB) photocatalyst was constructed for the effective degradation of antibiotics. Both the photocatalytic activity and photostability of g-C₃N₄/Bi₂WO₆ (gCB) were further improved after loading PDI. Under simulated sunlight illumination, the apparent rate constant of tetracycline (TC) degradation by PCB reached 2.6 times that of gCB. The photocatalytic activity of PCB still kept over 80% after 4 cycle experiments, while gCB only remained around 21%. The superior activity of PCB was ascribed to the synergism between the extended visible light absorption range through the participation of PDI cocatalyst and facilitated gCB-to-PDI photoelectron transfer. TC would finally be transformed into non-toxic ring opening products and mineralized. This work demonstrated that PDI was an excellent metal-free cocatalyst and exhibited great potential to boost the activity of photocatalysts.

Mechanism of a double-channel nitrogen-doped lignin-based carbon on the highly selective removal of tetracycline from water

A high-performance nitrogen-doped lignin-based carbon material (ILAC-N) was synthesized using industrial lignin and urea by hydrothermal and activation, as an absorbent of tetracycline hydrochloride (TC). The results showed that the ILAC-N comprises a double-channeled structure with micro and mesopores. It exhibits an excellent adsorption capacity of TC across a wide pH range (pH 2-11), with the highest adsorption capacity of 1396 mg g^-1 at 323 K. Tests in actual wastewater showed that the TC removal rate by ILAC-N exceeded 97.4%. Moreover, it maintained a removal rate of 84% after 10 regeneration cycles, revealing its high reusability. Mechanisms suggested that pore filling and π-π interaction played a critical role in this process. In conclusion, ILAC-N can be broadly applied to livestock manure and pharmaceutical wastewater treatment, owing to its high adsorption capacity, good adsorption properties across a wide pH range, excellent reusability. Furthermore, this research opens a new path for lignin utilization.

Biocatalytic membranes for combating the challenges of membrane fouling and micropollutants in water purification: A review

Over the last few years, the list of water contaminants has grown tremendously due to many anthropogenic activities. Various conventional technologies are available for water and wastewater treatment. However, micropollutants of emerging concern (MEC) are posing a great threat due to their activity at trace concentration and poor removal efficiency by the conventional treatment processes. Advanced technology like membrane technology can remove MEC to some extent. However, issues like the different chemical properties of MEC, selectivity, and fouling of membranes can affect the removal efficiency. Moreover, the concentrate from the membrane filtration may need further treatment. Enzymatic degradation of pollutants and foulants is one of the green approaches for removing various contaminants from the water as well as mitigating membrane fouling. Biocatalytic membranes (BCMs), in which enzymes are immobilized on membranes, combines the advantages of membrane separation and enzymatic degradation. This review article discussed various commonly used enzymes in BCMs for removing MEC and fouling. The majorly used enzymes were oxidoreductases and hydrolases for removing MEC, antifouling, and self-cleaning ability. The various BCM synthesis processes based on entrapment, crosslinking, and binding have been summarized, along with the effects of the addition of the nanoparticles on the performances of the BCMs. The scale-up, commercial viability, challenges, and future direction for improving BCMs have been discussed and shown bright possibilities for these new generation membranes.

Free and immobilized biocatalysts for removing micropollutants from water and wastewater: Recent progress and challenges

Enzymatic conversion of micropollutants into less-toxic derivatives is an important bioremediation strategy. This paper aims to critically review the progress in water and wastewater treatment by both free and immobilized enzymes presenting this approach as highly efficient and performed under environmentally benign and friendly conditions. The review also summarises the effects of inorganic and organic wastewater matrix constituents on enzymatic activity and degradation efficiency of micropollutants. Finally, application of enzymatic reactors facilitate continuous treatment of wastewater and obtaining of pure final effluents. Of a particular note, enzymatic treatment of micropollutants from wastewater has been mostly reported by laboratory scale studies. Thus, this review also highlights key research gaps of the existing techniques and provides future perspectives to facilitate the transfer of the lab-scale solutions to a larger scale and to improve operationability of biodegradation processes.

Highly effective enzymes immobilization on ceramics: Requirements for supports and enzymes

Enzyme immobilization is a well-known method for the improvement of enzyme reusability and stability. To achieve very high effectiveness of the enzyme immobilization, not only does the method of attachment need to be optimized, but the appropriate support must be chosen. The essential necessities addressed to the support applied for enzyme immobilization can be focused on the material features as well as on the stability and resistances in certain conditions. Ceramic membranes and nanoparticles are the most widespread supports for enzyme immobilization. Hence, the immobilization of enzymes on ceramic membrane and nanoparticles are summarized and discussed. The important properties of the supports are particle size, pore structure, active surface area, volume to surface ratio, type and number of reactive available groups, as well as thermal, mechanical, and chemical stability. The modifiers and the crosslinkers are crucial to the enzyme loading amount, the chemical and physical stability, and the reusability and catalytical activity of the immobilized enzymes. Therefore, the chemical and physical methods of modification of ceramic materials are presented. The most popular and used modifiers (e.g. APTES, CPTES, VTES) as well as activating agents (GA, gelatin, EDC and/or NHS) applied to the grafting process are discussed. Moreover, functional groups of enzymes are presented and discussed since they play important roles in the enzyme immobilization via covalent bonding. The enhanced physical, chemical, and catalytical properties of immobilized enzymes are discussed revealing the positive balance between the effectiveness of the immobilization process, preservation of high enzyme activity, its good stability, and relatively low cost.

Tetracycline antibiotics and NH4+ detection by Zn-organic framework fluorescent probe

A fluorescent probe based on single metal-organic framework material without additional fluorophores and active sites can significantly improve the stability of the probe for detection, and has very important application value in environmental analysis and detection. In this paper, a simple and rapid fluorescence detection method was established with Zn-MOF, which realized the highly sensitive detection of tetracycline antibiotics and NH₄⁺ in water. The prepared Zn-MOF has abundant pores and can exist stably in water. When tetracycline antibiotics are present in Zn-MOF aqueous solution, based on the unique coordination ability between Zn and N, tetracycline antibiotics rich in N will be adsorbed into the pore canals of MOF, and aggregation-induced luminescence will occur. The original non-fluorescent Zn-MOF will immediately produce yellow fluorescence, realizing the detection of tetracycline antibiotics in water, with the limit of detection reaching 0.017 μM in a linear range of 0.02-13 μM. Zn-MOF is further used for the detection of tetracycline antibiotics in actual samples of milk and honey. Oxytetracycline (OTC) with the best fluorescence response of tetracycline antibiotics was coated on Zn-MOF to synthesize OTC@Zn-MOF fluorescent probe. NH₄⁺ will replace the original ligand of Zn-MOF, which will disintegrate MOF and release OTC, resulting in a fluorescence decrease. Therefore, NH₄⁺ can be detected with low limit of detection (0.038 μM) in a linear range of 0 to 3 mM. The probe is expected to be able to detect ammonia in the environment.

Making Waves: Biocatalysis and Biosorption: Opportunities and Challenges Associated with a New Protein-Based Toolbox for Water and Wastewater Treatment

New water and wastewater treatment technologies are required to meet the demands created by emerging contaminants and resource recovery needs, yet technology development is a slow and uncertain process. Through evolution, nature has developed highly selective and fast-acting proteins that could help address these issues, but research and application have been limited, often due to assumptions about stability and economic feasibility. Here we highlight the potential advantages of cell-free, protein-based water and wastewater treatment processes (biocatalysis and biosorption), evaluate existing information about their economic feasibility, consider when a protein-based treatment process might be advantageous, and highlight key research needs.

Antibiotics in wastewater: From its occurrence to the biological removal by environmentally conscious technologies

In this critical review, we explored the most recent advances about the fate of antibiotics on biological wastewater treatment plants (WWTP). Although the occurrence of these pollutants in wastewater and natural streams has been investigated previously, some recent publications still expose the need to improve the detection strategies and the lack of information about their transformation products. The role of the antibiotic properties and the process operating conditions were also analyzed. The pieces of evidence in the literature associate several molecular properties to the antibiotic removal pathway, like hydrophobicity, chemical structure, and electrostatic interactions. Nonetheless, the influence of operating conditions is still unclear, and solid retention time stands out as a key factor. Additionally, the efficiencies and pathways of antibiotic removals on conventional (activated sludge, membrane bioreactor, anaerobic digestion, and nitrogen removal) and emerging bioprocesses (bioelectrochemical systems, fungi, and enzymes) were assessed, and our concern about potential research gaps was raised. The combination of different bioprocess can efficiently mitigate the impacts generated by these pollutants. Thus, to plan and design a process to remove and mineralize antibiotics from wastewater, all aspects must be addressed, the pollutant and process characteristics and how it is the best way to operate it to reduce the impact of antibiotics in the environment.

Pharmaceuticals removal by immobilized laccase on polyvinylidene fluoride nanocomposite with multi-walled carbon nanotubes

The presence of pharmaceutical micropollutants in water and wastewater is considered a serious environmental issue. To eliminate these pollutants, biodegradation of pharmaceuticals using enzymes such as laccase, is proposed as a green method. In this study, immobilized laccase was used for the removal of two model pharmaceutical compounds, carbamazepine and diclofenac. Polyvinylidene fluoride (PVDF) membrane modified with multi-walled carbon nanotubes (MWCNTs) were synthesized as a tailor-made support for enzyme immobilization. Covalently immobilized laccase from Trametes hirsuta exhibited remarkable activity and activity recovery of 4.47 U/cm² and 38.31%, respectively. The results also indicated improvement in the operational and thermal stability of the immobilized laccase compared to free laccase. Finally, by using immobilized laccase in a mini-membrane reactor, removal efficiencies of 27% in 48 h and 95% in 4 h were obtained for carbamazepine and diclofenac, respectively. The findings suggest that immobilized laccase on PVDF/MWCNT membranes is a promising catalyst for large-scale water and wastewater treatment which is also compatible with existing treatment facilities.

Recent advancement in remediation of synthetic organic antibiotics from environmental matrices: Challenges and perspective

Continuous discharge and persistence of antibiotics in aquatic ecosystem is identified as emerging environment health hazard. Partial degradation and inappropriate disposal induce appearance of diverse antibiotic resistant genes (ARGs) and bacteria, hence their execution is imperative. Conventional methods including waste water treatment plants (WWTPs) are found ineffective for the removal of recalcitrant antibiotics. Therefore, constructive removal of antibiotics from environmental matrices and other alternatives have been discussed. This review summarizes present scenario and removal of micro-pollutants, antibiotics from environment. Various strategies including physicochemical, bioremediation, use of bioreactor, and biocatalysts are recognized as potent antibiotic removal strategies. Microbial Fuel Cells (MFCs) and biochar have emerged as promising biodegradation processes due to low cost, energy efficient and environmental benignity. With higher removal rate (20-50%) combined/ hybrid processes seems to be more efficient for permanent and sustainable elimination of reluctant antibiotics.

Microbial degradation of tetracycline in the aquatic environment: a review

Tetracycline residues have frequently been detected in multi-environmental media, and it could induce antibiotic resistance genes (ARGs) in microorganisms, which has attracted great attention. Where biodegradation processes may be a promising strategy to remove tetracycline. Thus, this study mainly considers: (i) the degradation of tetracycline by microorganisms including single microorganisms and microbial flora; (ii) the elimination of tetracycline during biochemical treatment processes and advanced treatment systems in wastewater treatment plants (WWTPs) and constructed wetlands (CWs); (iii) the degradation of tetracycline by biological coupling processes; (iv) the confusion and problem of tetracycline biodegradation. Furthermore, the characteristics and comparison of tetracycline biodegradation have been discussed in detail. Additionally, future research directions are suggested to reduce tetracycline in the aquatic environment, especially tetracycline biodegradation and the nitrogen conversion process. Highlights Degradation of tetracycline by pure culture strains and microflora was significant. Degradation of tetracycline by biochemical treatment process was summarized. Advanced treatment process in CWs could eliminate tetracycline. Future research directions on biodegradation of tetracycline are proposed.

3D Chitin Scaffolds from the Marine Demosponge Aplysina archeri as a Support for Laccase Immobilization and Its Use in the Removal of Pharmaceuticals

For the first time, 3D chitin scaffolds from the marine demosponge Aplysina archeri were used for adsorption and immobilization of laccase from Trametes versicolor. The resulting chitin-enzyme biocatalytic systems were applied in the removal of tetracycline. Effective enzyme immobilization was confirmed by scanning electron microscopy. Immobilization yield and kinetic parameters were investigated in detail, in addition to the activity of the enzyme after immobilization. The designed systems were further used for the removal of tetracycline under various process conditions. Optimum process conditions, enabling total removal of tetracycline from solutions at concentrations up to 1 mg/L, were found to be pH 5, temperature between 25 and 35 °C, and 1 h process duration. Due to the protective effect of the chitinous scaffolds and stabilization of the enzyme by multipoint attachment, the storage stability and thermal stability of the immobilized biomolecules were significantly improved as compared to the free enzyme. The produced biocatalytic systems also exhibited good reusability, as after 10 repeated uses they removed over 90% of tetracycline from solution. Finally, the immobilized laccase was used in a packed bed reactor for continuous removal of tetracycline, and enabled the removal of over 80% of the antibiotic after 24 h of continuous use.

Characterization of a robust cold-adapted and thermostable laccase from Pycnoporus sp. SYBC-L10 with a strong ability for the degradation of tetracycline and oxytetracycline by laccase-mediated oxidation

A native laccase (Lac-Q) with robust cold-adapted and thermostable characteristics from the white-rot fungus Pycnoporus sp. SYBC-L10 was purified, characterized, and used in antibiotic treatments. Degradation experiments revealed that Lac-Q at 10.0 U mL^-1 coupled with 1.0 mmol L^-1 ABTS could degrade 100% of the tetracycline or oxytetracycline (50 mg L^-1) within 5 min with a static incubation at 0 °C (pH 6.0). The presence of the Mn²⁺ ion inhibited the removal rate of tetracycline and oxytetracycline by the Lac-Q-ABTS system, and the presence of Al³⁺, Cu²⁺, and Fe³⁺ accelerated the removal rate of tetracycline and oxytetracycline by the Lac-Q-ABTS system. Furthermore, the growth inhibition of Bacillus altitudinis SYBC hb4 and E. coli by tetracycline antibiotics revealed that the antimicrobial activity was significantly reduced after treatment with the Lac-Q-ABTS system. Finally, seven transformation products of oxytetracycline (namely TP 445, TP 431, TP 413, TP 399, TP 381, TP 367, and TP 351) were identified during the Lac-Q-mediated oxidation process by using UPLC-MS/MS. A possible degradation pathway including deamination, demethylation, and dehydration was proposed. These results suggest that the Lac-Q-ABTS system shows a great potential for the treatment of antibiotic wastewater containing different metal ions at various temperatures.

Biodegradation mechanism of tetracycline (TEC) by strain Klebsiella sp. SQY5 as revealed through products analysis and genomics

Although it has been proved that abiotic processes can transform tetracycline (TEC), little is known about how microbial processes may degrade TEC in aquatic environment. The objective of this study is to investigate the biodegradation pathway of TEC by strain Klebsiella sp. SQY5 and molecular mechanism of TEC resistance under the aerobic conditions. Effects of mycelium, intracellular, and extracellular enzyme on TEC degradation process were explored, suggesting that mycelium contributed the most of TEC degradation with a maximum efficiency of 58.64%. Biodegradation characteristic of TEC and its degradation products were studied. The results showed that nine possible biodegradation products were identified, and a potential biodegradation pathway was proposed including the removal of methyl, carbonyl, and amine groups. The functional genes of this bacterium were also determined by genomics, and analysis indicated that functional genes that could be relevant to hydrolysis, ring opening and oxidation played an important role in the process of TEC biodegradation. Results from this study can provide a theoretical basis for better estimating the fate, transportation, and degradation of antibiotics in aquatic environment.

Enzymatic Cascade Catalysis in a Nanofiltration Membrane: Engineering the Microenvironment by Synergism of Separation and Reaction

Microenvironment plays a significant role in enzymatic catalysis, which directly influences enzyme activity and stability. It is important to regulate the enzyme microenvironment, especially for the liquid with unfavored properties (e.g., pH and dissolved oxygen). In this work, we propose a methodology that can regulate pH and substrate concentration for enzymatic catalysis by a biocatalytic membrane, which is composed of glucose oxidase (GOx) and horseradish peroxidase (HRP) co-immobilized in a polyamide nanofiltration (NF) membrane (i.e., beneath the separation layer). By virtue of the selective separation function of NF membrane and in situ production of organic acid/electron donor with GOx, a synergism effect of separation and reaction in the liquid/solid interface was manipulated for engineering the microenvironment of HRP to enhance its activity and stability for micropollutant removal in water. The outcome of this work not only provides a new methodology to precisely control enzymatic reaction but also offers a smart membrane system to efficiently and steadily remove the micropollutants in portable water.

Multi-walled carbon nanotube/amino-functionalized MIL-53(Fe) composites: Remarkable adsorptive removal of antibiotics from aqueous solutions

A novel adsorbent composite was synthesized by combining amino-functionalized MIL-53(Fe) with multi-walled carbon nanotubes (MWCNT), and used to adsorb tetracycline hydrochloride (TCN) and chlortetracycline hydrochloride (CTC). The maximum adsorption capacities of TCN and CTC over MWCNT/NH₂-MIL-53(Fe) at 25 °C were 368.49 and 254.04 mg g^-1, which are, respectively, 1.79 and 8.37 times higher than that of chaff biochar. Interestingly, the mesoporosity of MWCNT/NH₂-MIL-53(Fe) significantly increased through introduction of MWCNT into NH₂-MIL-53(Fe), which proved to be favorable for the production of active adsorption sites. Besides, the remarkably increased adsorption capacity can be ascribed to the hydrogen bonding between amino functional groups on MWCNT/NH₂-MIL-53(Fe) and hydroxyl functional groups on TCN or CTC. Moreover, the π-π interaction between adsorbate and adsorbent was considered the main reason for the adsorption of TCN and CTC. The great adsorption capacity, as well as excellent reusability, demonstrated the potential application of MWCNT/NH₂-MIL-53(Fe) in the removal of TCN and CTC from aqueous solutions.

Impact of simultaneous retention of micropollutants and laccase on micropollutant degradation in enzymatic membrane bioreactor

This study systematically compares the performance of ultrafiltration (UF) and nanofiltration (NF) based enzymatic membrane bioreactors (EMBRs) for the degradation of five micropollutants, namely atrazine, carbamazepine, sulfamethoxazole, diclofenac and oxybenzone to elucidate the impact of effective membrane retention of micropollutants on their degradation. Based on the permeate quality, NF-EMBR achieved 92-99.9% micropollutant removal (i.e., biodegradation + membrane retention), while the removal of these micropollutants by UF-EMBR varied from 20 to 85%. Mass balance analysis revealed that micropollutant degradation was improved by 15-30% in NF-EMBR as compared to UF-EMBR, which could be attributed to the prolonged contact time between laccase and micropollutants following their effective retention by the NF membrane. A small decline in permeate flux was observed during EMBR operation. However, the flux could be recovered by flushing the membrane with permeate.

Laccases: Production, Expression Regulation, and Applications in Pharmaceutical Biodegradation

Laccases are a family of copper-containing oxidases with important applications in bioremediation and other various industrial and biotechnological areas. There have been over two dozen reviews on laccases since 2010 covering various aspects of this group of versatile enzymes, from their occurrence, biochemical properties, and expression to immobilization and applications. This review is not intended to be all-encompassing; instead, we highlighted some of the latest developments in basic and applied laccase research with an emphasis on laccase-mediated bioremediation of pharmaceuticals, especially antibiotics. Pharmaceuticals are a broad class of emerging organic contaminants that are recalcitrant and prevalent. The recent surge in the relevant literature justifies a short review on the topic. Since low laccase yields in natural and genetically modified hosts constitute a bottleneck to industrial-scale applications, we also accentuated a genus of laccase-producing white-rot fungi, Cerrena, and included a discussion with regards to regulation of laccase expression.

Degradation of tetracycline by immobilized laccase and the proposed transformation pathway

Magnetic cross-linked enzyme aggregates (M-CLEAs) were prepared for Cerrena laccase and used in antibiotic treatment. Of the seven antibiotics examined in this study, Cerrena laccase M-CLEAs were most effective in degradation of tetracycline (TC) and oxytetracycline (OTC), followed by ampicillin, sulfamethoxazole and erythromycin. The redox mediator ABTS was not able to improve efficiencies of degradation of TC and OTC. Cerrena laccase at 40U/mL eliminated 100μg/mL TC at pH 6 and 25°C in 48h in the absence of a redox mediator, with over 80% degradation occurring within the first 12h. Laccase treatment also significantly suppressed the antimicrobial activity of TC and OTC. Three TC transformation products, the levels of which initially increased and subsequently decreased during laccase treatment were identified by using LC-TOF MS. A mechanism of laccase-mediated TC oxidation was proposed based on the identified intermediates.

Multicriteria assessment of advanced treatment technologies for micropollutants removal at large-scale applications

With the introduction and discharge of thousands of new micropollutants (MPs) every year, traditional water and wastewater treatment plants may be incapable of tackling them all. With their low concentrations and diversity in nature, MP removal encounters numerous challenges. Although some MPs are effectively eliminated via conventional treatment methods, most of them can easily escape and are retained in the discharged effluent. Therefore, advanced methods such as (i) adsorption, (ii) oxidation and advanced oxidation processes (O3 and O3-based advanced oxidation processes, UV/H2O2), (iii) membrane processes, and (iv) membrane bioreactors, become an inevitable approach. Despite the unsurprisingly vast number of papers on MP treatment available at present, most of these studies were carried out at a laboratory scale while only a few pilot- and full-scale studies have experimented. Nevertheless, an in-depth assessment of real-world MP treatment methods is extremely crucial for practitioners. To date, no paper has been dedicated to look at this issue. Therefore, this paper aims to review these large-scale treatment methods. First, the paper goes through the regulations and standards which deal with MPs in water courses. It will then assess these methods in various case-studies with reference to different criteria towards serving as a reference for further practical applications.

Zeolitic imidazolate metal organic framework ZIF-8 with ultra-high adsorption capacity bound tetracycline in aqueous solution

Synthetic process of ZIF-8 and a mechanism of tetracycline bound to ZIF-8 due to electrostatic attraction and π–π stacking interaction.