Performance of microwave treatment for disintegration of cephalosporin mycelial dreg (CMD) and degradation of residual cephalosporin antibiotics

Characteristics of acidic hydrothermal treatment for disintegration of spiramycin fermentation residue and degradation of residual antibiotics

To recycle the nutrients in spiramycin (SPM) fermentation residue (SFR) through biological methods, acid hydrothermal treatment (AHT) was employed as pretreatment to enhance SFR biodegradability. The results showed that the degradation rate of residual SPM in SFR reached 100% after 120 min at 100℃ and 0.30 M acid with a 30.5% and 89.7% increase in proteins and polysaccharides, respectively. The SPM degradation was faster at higher acidity and temperature. However, elevated SPM concentration and the presence of protein, humic acid, and polysaccharide inhibited SPM degradation. The disintegration of SFR was evidenced by changes in its microstructure and could be predicted through the release of dissolved organic matter. Eight major SPM intermediates were identified with lower mutagenicity and antibacterial activity testing against Staphylococcus aureus. These results demonstrate that AHT not only disintegrates SFR but also degrades the residual SPM antibiotics, which implies the possibility for practical applications.

Safe utilization of bioresources in gentamicin mycelial residues by thermal treatment: Antibiotic degradation, resistance gene inactivation and available nutrients promotion

Gentamicin mycelium residues (GMRs) abundant in organic substances were generated during the production of gentamicin. Inappropriate handling techniques not only waste valuable resources, they could also result in residual gentamicin into the natural environment, leading to the generation of antibiotic resistance genes (ARGs), which would cause a significant threat to ecological system and human health. In the present work, the effects of thermal treatment on the removal of residual gentamicin in GMRs, as well as the changes of associated ARGs abundance, antimicrobial activity and bioresources properties were investigated. The results indicated that the hazards of GMRs was significantly reduced through thermal treatment. The degradation rate of residual gentamicin in GMRs reached 100 %, the total abundance of gentamicin resistance genes declined from 8.20 to 1.14 × 10-5 and the antibacterial activity of the decomposition products of GMRs on Vibrio fischeri was markedly reduced at 200 °C for 120 min. Additionally, the thermal treatment remarkably influenced the bioresource properties of GMRs-decomposition products. The release of soluble organic matters including soluble carbohydrates and soluble proteins have been enhanced in GMRs, while excessively high temperatures could lead to a reduction of nutrient substances. Generally, thermal treatment technology was a promising strategy for synergistic reducing hazards and utilizing bioresources of GMRs.

Fenton oxidation treatment of oxytetracycline fermentation residues: Harmless performance and bioresource properties

The pharmaceutical factories of oxytetracycline (OTC) massively produce OTC fermentation residues (OFRs). The high content of residual OTC and antibiotic resistance genes in OFRs must to be considered and controlled at an acceptable level. This study therefore investigated the applicability of Fenton oxidation in OTC degradation and resistant gene inactivation of OFRs. The results revealed that Fe²⁺ as catalyzer could very rapidly activate H₂O₂ to produce HO^•, leading to instantaneous degradation of OTC. The optimum conditions for OTC removal were 60 mM H₂O₂ and 140 mg/L Fe²⁺ under pH 7. After Fenton oxidation treatment, the release of water-soluble polysaccharides, NO₃-N, and PO₄-P was enhanced, whereas for proteins and NH₃-N were reduced. Three soluble fluorescence components (humic, tryptophan-like, and humic acid-like substances) were identified through fluorescence spectra with parallel factor analysis, and their reduction exceeded 50% after Fenton oxidation. There were twelve intermediates and three degradation pathways of OTC in OFRs during Fenton process. According to toxicity prediction, the comprehensive toxicity of OTC in OFRs was alleviated via Fenton oxidation treatment. In addition, Fenton oxidation showed the ability to reduce antibiotic resistance genes and mobile genetic elements, and even tetO, tetG, intI1, and intI2 were eliminated completely. These results suggested that Fenton oxidation treatment could be an efficient strategy for removing OTC and resistance genes in OFRs.

Influence of thermally activated peroxodisulfate pretreatment on gaseous emission, dissolved organic matter and maturity evolution during spiramycin fermentation residue composting

Aerobic composting combined with appropriate pretreatment is promising to achieve the utilization of antibiotics fermentation residues (AFRs). This research studied the effect of thermally activated peroxodisulfate (TAP) pretreatment on greenhouse gas (GHGs) emission, dissolved organic matter (DOM) and maturity evaluation during spiramycin fermentation residue (SFR) composting. Three treatments were conducted from co-composting of SFR and wheat straw, while 90% and 99.9% residual spirmycin removal pretreatment SFR by TAP were provided and compared with raw SFR. The cumulative CO₂ and NH₃ emissions increased by 17.2% and 30.8% after TAP pretreatment removed 99.9% residual spiramycin in SFR, while the cumulative CH₄ and N₂O emission decreased by 34.0% and 5.27%, respectively. The DOM, humic acid (HA)/fulvic acid (FA) and NH₄⁺/NO₃^- analysis confirmed that the composting maturity was improved with the increasing of HA and NO₃^- content by TAP pretreatment.

Preparation of phosphoric acid modified antibiotic mycelial residues biochar: Loading of nano zero-valent iron and promotion on biogas production

Antibiotic mycelial residues (AMRs), as recyclable hazardous waste, can realize efficient utilization by reasonable treatment. To solve the problems of undeveloped pore structure and low specific surface area existed in AMR biochar, this study first modified biochar by phosphoric acid (H₃PO₄) to prepare PBC (H₃PO₄-modified biochar). Then, PBC was used as carrier to load nano zero-valent iron (nZVI) for preparation of nZVI/PBC. Finally, the biochar materials were used to promote anaerobic digestion (AD) of corn straw. The results showed that H₃PO₄-modification can effectively improve the specific surface area, pore structure, and electron donating capacity of AMRs biochar. The using of PBC as carrier to load nZVI attenuated the agglomeration of nZVI particles. Both PBC and nZVI/PBC improved the AD process, with biogas yield enhanced by 29.63% and 29.26%, respectively. The nZVI/PBC exhibited higher ability in maintaining the stability of AD system and promotion of fiber degradation than PBC.

Insight into the evolution of antibiotic resistance genes and microbial community during spiramycin fermentation residue composting process after thermally activated peroxydisulfate pretreatment

Previous research has been demonstrated that the residual unextracted antibiotics in spiramycin fermentation residue (SFR) could be efficiently removed by thermally activated peroxodisulfate (TAP) pretreatment, indicating the improvement of biodegradability. This study aimed to investigate the effect of TAP pretreatment on the succession of bacterial community and fate of antibiotic resistance genes (ARGs) during SFR composting. Results indicated that TAP pretreatment increased the composting temperature and promoted the decomposition of organic matters. Furthermore, TAP pretreatment could increase bacterial alpha diversity and significantly reduce the relative abundance of ARGs (1.13-1.75 times) and mobile genetic elements (MGEs) (1.13-1.32 times) after composting. The compost of pretreated SFR by TAP could reduce the enrichment of ARGs and MGEs in the bacterial community, especially the rRNA methylase genes of ermB (4-142-folds). Redundancy analysis showed that Actinobacteria, Bacteroidetes, Proteobacteria and horizontal gene transfer mediated by MGEs (intI1) was positively related to the changes in ARGs (accounted for 97.4%). Network analysis showed that Firmicutes was the main bacterial hosts of ARGs and MGEs. These findings demonstrated that TAP pretreatment combined composting was a promising strategy for SFR safe treatment and disposal that could reduce the proliferation and transfer of ARGs.

Responses of methane production, microbial community and antibiotic resistance genes to the mixing ratio of gentamicin mycelial residues and wheat straw in anaerobic co-digestion process

Anaerobic co-digestion (AcoD) of gentamicin mycelial residues (GMRs), a kind of nitrogen-rich biowaste, and wheat straw (WS) is an attractive technology for the recycling of GMRs. However, the effects of the co-substrate ratio on methane production, system stability and antimicrobial resistance during co-digestion remain unclear. Thus, this study aimed to fill in the blanks through AcoD of GMRs and WS with different mixing ratios (1:0, 2:1, 1:1, 1:2, 0:1, VS basis) via batch tests. Results showed that AcoD facilitated methane production than mono anaerobic digestion and reduced the accumulation of the toxic substances, such as ammonia nitrogen and humic-like substances. The maximum methane production was obtained at the reactors with the mixing ratio of 1:1 and 1:2 (R-1:1 and R-1:2), which matched with the relative abundance of key enzymes related to methanogenesis predicted by PICRUSt. Microbial community analysis indicated that Methanosaeta was the most dominant methanogen in the AcoD reactors. The highest relative abundance of Methanosaeta (45.1%) was obtained at R-1:1 due to the appropriate AcoD conditions, thus, providing greater possibilities for high stability of AcoD system. Additionally, AcoD of the GMRs and WS under the mixing ratio of 1:1 and 1:2 did not prompt the increase of antibiotic resistance genes (ARGs). Not only that, the likelihood of horizontal gene transfer declined in R-1:1 due to the weaker connection and transport between host and recipient bacteria. Findings of this study suggested that the suitable mixing ratio of GMRs and WS contributes to methane production and system stability, and reduces the dissemination risks of ARGs.

Emission Characteristics of NOx and SO2 during the Combustion of Antibiotic Mycelial Residue

The antibiotic mycelial residue (AMR) generated from cephalosporin C production is a hazardous organic waste, which is usually disposed of by landfilling that causes potential secondary environmental pollution. AMR combustion can be an effective method to treat AMR. In order to develop clean combustion technologies for safe disposal and energy recovery from various AMRs, the emission characteristics of NO_x and SO₂ from AMR combustion were studied experimentally in this work. It was found that the fuel-N is constituted by 85% protein nitrogen and 15% inorganic nitrogen, and the fuel-S by 78% inorganic sulfur and 22% organic sulfur. Nitrogen oxide emissions mainly occur at the volatile combustion stage when the temperature rises to 400 °C, while the primary sulfur oxide emission appears at the char combustion stage above 400 °C. Increasing the combustion temperature and airflow cause higher NO_x emissions. High moisture content in AMR can significantly reduce the NO_x emission by lowering the combustion temperature and generating more reducing gases such as CO. For the SO₂ emission, the combustion temperature (700 to 900 °C), airflow and AMR water content do not seem to exhibit obvious effects. The presence of CaO significantly inhibits SO₂ emission, especially for the SO₂ produced during the AMR char combustion because of the good control effect on the direct emission of inorganic SO₂. Employing air/fuel staging technologies in combination with in-situ desulfurization by calcium oxide/salts added in the combustor with operation temperatures lower than 900 °C should be a potential technology for the clean disposal of AMRs.

Degradation of antibiotic Cephalosporin C in different water matrices by ionizing radiation: Degradation kinetics, pathways, and toxicity

Cephalosporin antibiotics are ubiquitous emerging pollutants in various aquatic environments due to their extensive production and application. Herein, the radiolytic degradation of antibiotic Cephalosporin C (CEP-C) in different water matrices was comprehensively investigated using gamma radiation at various experimental conditions. The results revealed that CEP-C oxidation obeyed pseudo first-order kinetics, and 100%, 94.9%, 67.0%, 44.6% and 34.5% removal of CEP-C with 10-200 mg/L was achieved at 0.4 kGy, respectively. The degradation was faster at higher absorbed dose and acidic conditions (pH = 3.5). The inorganic anions, including SO₄^2-, NO₃^-, and HCO₃^-, had negative influence on the degradation of CEP-C, the corresponding rate constant decreased from 4.603 to 3.667, 1.677 and 2.509 kGy^-1 respectively in the presence of SO₄^2-, NO₃^-, and HCO₃^-. The analysis of intermediate products indicated that CEP-C was oxidized to generate about 10 intermediate products. Besides, it was inferred that the thioether sulfur oxidation, β-lactam ring opening, acetyl dissociation from dihydrothiazine ring and D-α-aminohexylamide group abscission were the major reaction mechanisms of CEP-C degradation by gamma radiation. Importantly, the antibacterial activity of CEP-C could be completely vanished by gamma radiation alone, while more toxic intermediate products might be formed. Addition of hydrogen peroxide and peroxymonosulfate could significantly improve the CEP-C degradation, and reduce the toxicity of intermediates of CEP-C degradation. Similar degradation behavior was observed in the groundwater and wastewater, implying that ionizing radiation can be used for degradation of Cephalosporin in water and wastewater.

l-Cysteine directing synthesis of BiOBr nanosheets for efficient cefazolin photodegradation: The pivotal role of thiol

Cefazolin (CFZ) is widely present in the wastewater treatment effluents and in receiving waters and has caused severe impacts to the ecosystem. CFZ degradation by photocatalysis has attracted increasing attention due to its eco-friendly features. Herein, we presented a green synthesis strategy for a highly active BiOBr photocatalyst for CFZ removal with L-cysteine as a directing agent, and the role of thiol in cysteine for facets control and morphology regulation was discussed. We found that the photoactivity of cysteine-induced BiOBr nanosheet was much higher than those prepared by using arginine and glycine as directing agent. Further experiments showed that the cysteine preferentially coordinated Bi³⁺ with thiol rather than carboxyl. The strong interactions of thiol group with the external surface of the BiOBr crystals stabilize the small crystals that have high surface energy without the cysteine. Such a chemical environment favors forming BiOBr crystalline with small size of high surface area and oriented growth in [110] direction, which facilitates the photogenerated electron-hole separation to achieve significantly promoted photocatalytic activity. Moreover, the cysteine-directed BiOBr nanosheets displayed good photoreactivity to more pollutants (i.e. rhodamine B, cefradine and cefoperazone sodium) and excellent reusability as verified via seven consecutive recycle experiments. The proper photocatalyst dosage (0.4 g/L), relatively acidic water environment (pH 3.4) and high temperature (35 °C) would be beneficial to CFZ photodegrdation by BiOBr. Also, the CFZ photodegradation mechanism and degradation pathway were also proposed by combining radical trapping experiments and electron spin resonance (ESR) test with LC-MS analysis in the photocatalytic process.

A new approach to recycling cephalosporin fermentation residue into plant biostimulants

Cephalosporin fermentation residue (CFR), a byproduct of the pharmaceutical industry, mainly contains the mycelial biomass and unutilized culture medium, which can be reused as a high-quality protein source. This study first reports the recycling CFR into plant biostimulants using partial acid hydrolysis. Temperature, reaction time and ratio of hydrochloric acid/dry matter (H/S) were optimized for yielding both free amino acid and low molecular weight fraction based on response surface methodology. The crude protein concentration of CFR is 55%, with glutamic acid being the dominant amino acid (12.5%). Two favorable hydrolysis conditions were obtained: (1) 140 °C, 10.7 h, 17 H/S for maximizing the amino acid yield of 45.5 g/100 g CFR dw and (2) 100 °C, 10.7 h, 19 H/S for maximizing the low molecular weight fraction of 28.2%. The CFR-derived biostimulants obtained from two optimum conditions possessed two biostimulant modes of action: plant growth promotors/inhibitors and stress alleviators. However, they showed the differences in aminograms and profiles of low molecular weight compounds. Neither residual cephalosporin C nor its byproduct was detected in the CFR-derived biostimulants, suggesting that partial acid hydrolysis appears capable of recycling CFR into plant biostimulant safely.

Effect of co-digestion of tylosin fermentation dreg and food waste on anaerobic digestion performance

In this study, the effects of adding different food waste proportions (volatile solids ratio of 3:7, 5:5, 7:3) to tylosin fermentation dreg on anaerobic digestion were investigated. The results showed that the co-digestion group (294-399 mL·g-VS^-1) increased methane production by 14.8%-55.5% compared with tylosin fermentation dreg alone-digestion (256 mL·g-VS^-1). The correlation analysis showed that pH, total volatile fatty acids and acetic acid were the most important factors affecting cumulative methane production. Tylosin in the solid and liquid phases decreased significantly after anaerobic digestion, indicating that tylosin could be effectively removed by co-digestion, and the total removal rate was 68.2%-83.7%. Therefore, due to the satisfactory methane yield and the tolerable tylosin removal rate, it is feasible to make the co-digestion of tylosin fermentation dreg and food waste.

Green and efficient degradation of cefoperazone sodium by Bi4O5Br2 leading to the production of non-toxic products: Performance and degradation pathway

Photocatalytic process represents a promising approach to overcome the pollution challenge associated with the antibiotics-containing wastewater. This study provides a green, efficient and novel approach to remove cephalosporins, particularly cefoperazone sodium (CFP). Bi₄O₅Br₂ was chosen for the first time to systematically study its degradation for CFP, including the analysis of material structure, degradation performance, the structure and toxicity of the transformation products, etc. The degradation rate results indicated that Bi₄O₅Br₂ had an excellent catalytic activity leading to 78% CFP removal compared with the pure BiOBr (38%) within 120 min of visible light irradiation. In addition, the Bi₄O₅Br₂ presents high stability and good organic carbon removal efficiency. The effects of the solution pH (3.12 - 8.75) on catalytic activity revealed that CFP was mainly photocatalyzed under acidic conditions and hydrolyzed under alkaline conditions. Combined with active species and degradation product identification, the photocatalytic degradation pathways of CFP by Bi₄O₅Br₂ was proposed, including hydrolysis, oxidation, reduction and decarboxylation. Most importantly, the identified products were all hydrolysis rather than oxidation byproducts transformed from the intermediate of β-lactam bond cleavage in CFP molecule, quite different from the mostly previous studies. Furthermore, the final products were demonstrated to be less toxic through the toxicity analysis. Overall, this study illustrates the detailed mechanism of CFP degradation by Bi₄O₅Br₂ and confirms Bi₄O₅Br₂ to be a promising material for the photodegradation of CFP.

Pyrolysis of antibiotic mycelial dreg and characterization of obtained gas, liquid and biochar

The disposal and utilization of antibiotic mycelial dreg (AMD), which has been identified as a hazardous waste in China, are a serious concern because of the residual antibiotic and huge annual output. Pyrolysis is a promising technology to treat AMD. However, the pyrolysis of AMD is not studied in an adequate degree, particularly no attention has been paid to the release and distribution of the phosphorus in AMD during pyrolysis. Therefore, the present work studied the pyrolysis of AMD more comprehensively. The influence of pyrolysis temperature on product yields and characteristics, together with the release and distribution of nitrogen and phosphorus, and the antibiotic residue in products, were investigated. The results suggested that residual antibiotic was eliminated after pyrolysis. Nitrogen was mainly contained in the biochar and liquid products, while phosphorus was mainly retained in the biochar. Liquid products were characterized by abundant oxygen and nitrogen-containing compounds, while biochar was featured of both abundant nitrogen and inorganic phosphate groups. Pyrolysis temperature showed a significant effect on product yields and characteristics, and a low pyrolysis temperature is recommended considering the recycling of nitrogen and phosphorus. The disposal of AMD through pyrolysis conforms to the principles of AMD disposal.

Anaerobic digestion of spectinomycin mycelial residues pretreated by thermal hydrolysis: removal of spectinomycin and enhancement of biogas production

Anaerobic digestion (AD) is an effective technology to dispose antibiotic mycelial residues, but biogas production is influenced by hydrolysis rates and antibiotic residue. Herein, the effects of thermal hydrolysis pretreatment for AD of spectinomycin mycelial residues (SMRs) were investigated. The results showed that the removal ratio of spectinomycin was increased while the temperature of pretreatment was escalating. Meanwhile, thermal hydrolysis facilitated the dissolution of organic matters. However, non-biodegradable substances measured by fluorescence excitation-emission matrix accumulated and thus had an adverse influence on biogas production. Based on batch assays, the optimal pretreatment temperature for SMRs was 120 °C. The removal of spectinomycin was benefit for biogas production (increasing by 7.6%), and the overall biogas production increased by 27.6% compared with 289.90 mL gVS^-1 of untreated SMRs. The microbial community analysis revealed that spectinomycin (265 mg L^-1) might influence bacteria in the early stage of AD (first 5 days), while redundancy analysis showed that spectinomycin had a non-significant influence on community succession over the 32 days of fermentation.

Ultrasound wave assisted removal of Ceftriaxone sodium in aqueous media with novel nano composite g-C3N4/MWCNT/Bi2WO6 based on CCD-RSM model

The aim of this study was ultrasound assisted removal of Ceftriaxone sodium (CS) based on CCD model. Using sonochemical synthesized Bi₂WO₆ implanted on graphitic carbon nitride/Multiwall carbon nanotube (g-C₃N₄/MWCNT/Bi₂WO₆). For this purpose g-C₃N₄/MWCNT/Bi₂WO₆ was synthesized and characterized using diverse approaches including XRD, FE-SEM, XPS, EDS, HRTEM, FT-IR. Then, the contribution of conventional variables including pH, CS concentration, adsorbent dosage and ultrasound contact time were studied by central composite design (CCD) under response surface methodology (RSM). ANOVA was employed to the variable factors, and the most desirable operational conditions mass provided. Drug adsorption yield of 98.85% obtained under these defined conditions. Through conducting five experiments, the proper prediction of the optimum point were examined. The respective results showed that RSD% was lower than 5% while the t-test confirmed the high quality of fitting. Langmuir isotherm equation fits the experimental data best and the removal followed pseudo-second order kinetics. The estimation of the experimentally obtained maximum adsorption capacities was 19.57 mg.g^- of g-C₃N₄/MWCNT/Bi₂WO₆ for CS. Boundary layer diffusion explained the mechanism of removal via intraparticle diffusion.

Electrochemical oxidation of ceftazidime with graphite/CNT-Ce/PbO2-Ce anode: Parameter optimization, toxicity analysis and degradation pathway

In this work, the electrochemical degradation of antibiotic ceftazidime has been studied using a novel rare earth metal Ce and carbon nanotubes codoped PbO₂ electrode. A competitively high oxygen evolution potential (2.4 V) and enhanced catalytic surface area were obtained, evidence by LSV and CV electrochemical characterization. The G/CNT-Ce/PbO₂-Ce electrode possessed a more compact structure and a smaller grain size than the other PbO₂ and Ce-PbO₂ electrodes, exhibiting a prolonged service lifetime, evidence by accelerated lifespan test and recycling degradation experiment. As electrolysis time reached 120 min, the removal efficiency of ceftazidime and TOC arrived at 100.0% and 54.2% respectively in 0.05 M Na₂SO₄ solution containing 50 mg⋅L^-1 ceftazidime. The effect of applied current density, pH value, initial ceftazidime concentration and chloride contents on the degradation performance were systematically evaluated. The results demonstrated that electrochemical oxidation of ceftazidime over the G/CNT-Ce/PbO₂-Ce electrode was highly effective, and the mineralization rate was greatly improved, compared with pristine PbO₂ electrode. Considering the toxicity was increased after 30 min electrolysis, the intermediates were quantitatively investigated through HPLC-MS, GC-MS and IC technology. According to the identified products, a reaction mechanism has been proposed and pyridine and aminothiazole were detected with concentration from approximately 1 to 3 mg⋅L^-1, which were regarded as toxic byproducts during electrooxidation. Further electrocatalyzing by ring cleavage reaction and complete mineralization to CO₂, NO₃^- and NH₄⁺ was proposed, which demonstrated the G/CNT-Ce/PbO₂-Ce electrode exhibited high efficiency for ceftazidime removal in mild conditions.

Degradation of aqueous cefotaxime in electro-oxidation - electro-Fenton -persulfate system with Ti/CNT/SnO2-Sb-Er anode and Ni@NCNT cathode

Due to the potential threatening of antibiotics in aqueous environment, a novel electro-oxidation (EO) - electro-Fenton (EF) -persulfate (PS) system with the addition of peroxydisulfate and Fe²⁺ was installed for the degradation of cefotaxime. Ti/CNT/SnO₂-Sb-Er with an ultra-high oxygen evolution potential (2.15 V) and enhanced electrocatalytic surface area was adopted as anode. The OH production and electrode stability test demonstrated great improvement in the electrochemical performances. Ni@NCNT cathode was tested with higher H₂O₂ generation by the presence of nitrogen functionalities due to the acceleration of electron transfer of O₂ reduction. Experiment results indicated CNT and ErO₂ modification increased the molecular and TOC removal of cefotaxime. Coupling processes of EO-EF and EO-PS both resulted in shorter electrolysis time for complete cefotaxime removal, however, the mineralization ability of EO-PS process was lower than EO-EF, which might result from the immediate vanishing of PS. Thus, a further improved treatment EO-EF-PS system achieved an 81.6% TOC removal towards 50 mg L^-1 cefotaxime after 4 h electrolysis, under the optimal working condition Fe²⁺ = PS = 1 mM. The influence of current density and initial concentration on the performance of all processes was assessed. Methanol and tert-butanol were added in the system as OH and SO₄^- scavengers, which illustrating the mechanism of EO-EF-PS oxidizing process was the result of the two free radicals. Major intermediates were deduced and the degradation pathway of cefotaxime was analyzed. This research provides a potential coupling process with high antibiotic removal efficiency and effective materials for practical uses.

Variations of physical and chemical properties in relation to erythromycin mycelial dreg dewaterability under heat-activated persulfate oxidation conditioning

Erythromycin mycelial dreg (EMD) resulting from erythromycin (ERY) production process may be used as a nutrient resource. However, it has a high moisture content, which makes handling operations complicated. In this study, the EMD dewaterability under heat-activated persulfate (PS) oxidation conditioning was investigated. The variations of physical and chemical properties of EMD were further investigated to uncover the underlying mechanism of EMD dewaterability. Results indicated that EMD dewaterability was worse under single heat process, but significantly improved under heat-activated PS oxidation process. Heat-activated PS oxidation conditioning was capable to increase zeta potential, reduce median particle size, alter EMD flocs morphology, and disrupt mycelial cells. Concurrently, heat-activated PS oxidation conditioning resulted in the decrease of protein in tightly bound (TB) extracellular polymeric substances (EPS) and total EPS, and the decrease of fluorescing constituents (tryptophan protein, tyrosine protein and tryptophan amino acid) in EPS. Furthermore, a possible mechanism was proposed for heat-activated PS oxidation conditioning.

Degradation of antibiotics and antibiotic resistance genes in erythromycin fermentation residues using radiation coupled with peroxymonosulfate oxidation

Ionizing radiation coupled with peroxymonosulfate (PMS) oxidation was developed to degrade antibiotics and antibiotic resistance genes (ARGs) from the erythromycin fermentation (EryF) residual wastes. The experimental results showed that the ERY content and ARGs abundance decreased with increase of the absorbed dose and PMS dosage and gamma irradiation was more effective to abate ARGs from the EryF wastes. The removal efficiency of ERY reached 49-55% and more than 96-99% of ARGs (1.32-2.55 log) was eliminated with the absorbed dose of 25-50 kGy and PMS dosage of 50-100 mM. Illumina pyrosequencing revealed that 3 bacterial phyla, Proteobacteria, Firmicutes and Fusobacteria were highly enriched and the ARGs-linked hosts were affiliated to the genera Aeromonas, Enterobacteriaceae and Enterobacter in the phylum Proteobacteria. The abundance of the ARGs-linked bacteria decreased by gamma/PMS treatment. Ionizing radiation/PMS treatment with the doses of 25 kGy and 50 mM PMS is proposed for potential practical application.

An overview of cephalosporin antibiotics as emerging contaminants: a serious environmental concern

Antibiotics have been categorized as emerging pollutants due to their indiscriminate usage, continuous input and persistence in various environmental matrices even at lower concentrations. Cephalosporins are the broad-spectrum antibiotics of β-lactam family. Owing to its enormous production and consumption, it is reported as the second most prescribed antibiotic classes in Europe. The cephalosporin wastewater contains toxic organic compounds, inorganic salts, and active pharmaceutical ingredients (API) which pose a potential threat to the organisms in the environment. Therefore, removal of cephalosporin antibiotics from the environment has become mandatory as it contributes to increase in the level of chemical oxygen demand (COD), causing toxicity of the effluent and production of cephalosporin-resistant microbes. So far, several processes have been reported for degradation/removal of cephalosporins from the environment. A number of individual studies have been published within the last decade covering the various aspects of antibiotics. However, a detailed compilation on cephalosporin antibiotics as an emerging environmental contaminant is still lacking. Hence, the present review intends to highlight the current ecological scenario with respect to distribution, toxicity, degradation, various remediation technologies, and the regulatory aspects concerning cephalosporins. The latest successful technologies for cephalosporin degradation/removal discussed in this review will help researchers for a better understanding of the nature and persistence of cephalosporins in the environment along with the risks associated with their existence. The research thrust discussed in this review will also evoke new technologies to be attempted by the future researchers to develop sustainable options to remediate cephalosporin-contaminated environments.

Thermal characteristics and product formation mechanism during pyrolysis of penicillin fermentation residue

This work studied thermal characteristics and product formation mechanism during pyrolysis of penicillin fermentation residue (PR). Results showed that PR pyrolysis proceeded in four stages. The kinetic triplet of each stage was calculated using Flynn-Wall-Ozawa, Kissinger-Akahira-Sunose, and integral master-plot methods. The kinetic model for stage 1 was the three-dimensional diffusion model, the simple reaction order model for stage 2 and stage 4, and the nucleation-growth model for stage 3. FTIR analysis suggested that the intensities of absorption peaks of NH, CO, CH, CN, and CO in chars weakened gradually with increasing temperature, corresponding to the production of CH₄, CO, NH₃, and HCN. GC-MS results indicated that the high protein content in PR resulted in a high fraction of nitrogenated compounds (amides and amines, nitriles, and N-heterocyclic species) in bio-oil. The formation mechanism of these compounds was discussed. Besides, bio-oil also contained large quantities of oxygenated compounds and a few hydrocarbons.

The biodegradation of cefuroxime, cefotaxime and cefpirome by the synthetic consortium with probiotic Bacillus clausii and investigation of their potential biodegradation pathways

Cephalosporin residues in the environment are a great concern, but bioremediation options do exist. Bacillus clausii T reached a removal rate of 100% within 8 h when challenged with a mixture of cefuroxime (CFX), cefotaxime (CTX), and cefpirome (CPR). The co-culture of B. clausii T and B. clausii O/C displayed a higher removal efficiency for the mixture of CFX, CTX and CPR than a pure culture of B. clausii O/C. B. clausii T alleviated the biotoxicity of CFX and CPR. What's more, the biotoxicity of for CFX and CPR transformation products released by the co-culture of B. clausii T and B. clausii O/C was lower than that in pure cultures. Real-time PCR was applied to detect the changes in the expression levels of the relevant antibiotic-resistance genes of B. clausii T during CFX and CPR degradation. The results indicated that CFX and CPR enhanced the expression of the β-lactamase gene bcl1. Hydrolysis, deacetylation and decarboxylation are likely the major mechanisms of CTX biodegradation by B. clausii. These results demonstrate that B. clausii T is a promising strain for the bioremediation of environmental contamination by CFX, CTX, and CPR.

Hydrothermal treatment of lincomycin mycelial residues: Antibiotic resistance genes reduction and heavy metals immobilization

In this study, fate of antibiotic resistance genes (ARGs - lmrA, lmrB, ermB, lnuA, lnuB and vgaC) and species distribution of heavy metals during lincomycin mycelial residues hydrothermal treatment (HT) process were investigated. The results showed that HT could reduce both ARGs and mobile genetic elements effectively by 1.02 to 4.14 logs. Total bacterial biomass reflecting by 16S rRNA decreased from 1.27 × 10⁹ to 4.47 × 10⁵ copies g^-1 dry weight. Moreover, half-lives of these targets varied from 2.4 min (ermB) to 8.9 min (lmrB) in the first 30 min of treatment based on a biphasic first-order kinetic model. After the first 30 min, however, half-lives ranged between 15.4 min (lmrA) and 247.6 min (ISCR1). Complexation and precipitation resulted in the transformation of heavy metals from weakly bounded to relatively stable fraction in HT process. Simultaneously, their environmental risk level decreased by at least one grade.

Investigating the environmental risks from the use of spray-dried cephalosporin mycelial dreg (CMD) as a soil amendment

Cephalosporin mycelial dreg (CMD) is a by-product of the pharmaceutical industry. Spray-drying is widely used for the dewatering process prior to the application of CMD as a soil amendment. However, the potential environmental behaviors and risks of spray-dried CMD amendment remain unclear. Here, a lab-scale incubation experiment was conducted to investigate the salinity, phytotoxicity, introduced antibiotics, heavy metals and the potential impacts of resistance genes in CMD-amended soil. Spray-dried CMD amendment generally increased soil salinity and only high dosed soils showed phytotoxic effects at the end of the incubation period, implying the physiological damage to plant growth. The introduced antibiotics quickly degraded over time, indicating a relatively low environmental persistence. Heavy metal slightly increased in soil receiving spray-dried CMD, and regulations should be developed to avoid metal accumulation. A decreased diversity and distinct patterns of β-lactam resistance genes as well as a dose-effect of their enrichment were observed in CMD-amended soil, which might be partially explained by the specific metals and introduced antibiotics. Antibiotic resistance genes in soil may be a valuable tool for evaluating the environmental risk associated with use of CMD as a soil amendment.

Removal of refractory organic pollutants in reverse-osmosis concentrated leachate by Microwave-Fenton process

A microwave-Fenton technology was applied to dispose of the reverse-osmosis concentrated leachate. Influential factors on the treatment of concentrated leachate with the pure Fenton and microwave-Fenton method were investigated. For the conventional Fenton process, the removal efficiencies of chemical oxygen demand (COD_Cr), UV₂₅₄, and the color number (CN) reached 84%, 87%, and 96%, respectively, with the biodegradability (BOD₅/COD_Cr) increased from 0.13 to 0.51 at an initial pH of 5.0, Fe²⁺ of 0.04 mol/L, a n(H₂O₂)/n(Fe²⁺) ratio of 8 after a reaction time of 3 h. When incorporating the Fenton process with microwave irradiation, a comparative COD_Cr and UV₂₅₄, and the CN removal rate of 75%, 83%, and 95%, and a high BOD₅/COD_Cr of 0.62 were achieved under a microwave power of 390 W and an extremely shortened reaction time of only 8 min. Meanwhile, sludge quantity showed a reduction of 24.7%, decreased from 8.50 g/L to 6.40 g/L after the participation of microwave. In addition, molecular-weight fraction (MWF), UV-visible spectrum (UV-vis), and 3D-EEM spectrum tests demonstrated that the macromolecular and complex organic compounds in the wastewater were significantly decomposed into small molecular matters. Our results found that microwave-Fenton is a promising technology for concentrated leachate treatment, with much shorter reaction time, lower sludge production, and enhanced biodegradability, as well as comparative organic matter removal performance.

Application of microwave-pretreated cephalosporin mycelial dreg (CMD) as soil amendment: Temporal changes in chemical and fluorescent parameters of soil organic matter

Land application of treated cephalosporin mycelial dreg (CMD) as a soil amendment is an alternative to its disposal in landfills and incineration because it has environmental and agronomic benefits. This study validated the efficacy of using the dewatered, microwave-pretreated CMD as a soil amendment. Pot experiments were conducted to assess the temporal changes in soil organic matter (SOM) profiles via chemical and fluorescent parameters. During the ageing period, the CMD-treated soil experienced a sudden rise in soil pH and soil electrical conductivity, along with a rapid decline in soil organic carbon and soil organic nitrogen content. The specific Ex/Em peak related to protein-like substances gradually disappeared, while those related to humic acid-like substances continued to increase thereafter. Fluorescence regional integration (FRI) results showed an ascended P_V,n/P_III,n index (1.94) and significant correlations with chemical data (M²=0.2875, r=0.8441, P<0.001, 999 permutations for Procrustes analysis). Taken together, despite the temporal changes in chemical and fluorescent data after soil conditioning, the increased content of SOM containing humic acid-like substances was observed at the end of the incubation period compared with control soil samples, indicating that the microwave-pretreated CMD might be applied as a soil amendment.