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

Detoxification of vancomycin fermentation residue by hydrothermal treatment and pyrolysis: Chemical analysis and toxicity tests

Vancomycin fermentation residue (VFR) is a by-product of the pharmaceutical industry with high ecotoxicity caused by the residual antibiotics, antibiotic resistance genes (ARGs), and heavy metals (HMs). In this study, the detoxification effect of hydrothermal treatment (HT) and pyrolysis for VFR was assessed using chemical analysis and toxicity tests. When VFR was subjected to HT and pyrolysis at ≥400 °C, more than 99.70 % of the residual vancomycin and all ARGs were removed. The HMs contents in VFR followed the order of manganese (676.2 mg/kg) > zinc (148.6 mg/kg) > chromium (25.40 mg/kg) > copper (17.20 mg/kg), and they were highly bioavailable and easily leached. However, HT and pyrolysis (≥400 °C) substantially reduced the bioavailable fractions and leaching properties of the HMs. After HT and pyrolysis at ≥ 400 °C, the potential ecological risk of HMs in VFR was reduced from considerable to moderate/low levels. The elutriate acute toxicity test suggested that HT and pyrolysis at ≥ 400 °C effectively reduced the toxicity of VFR to an acceptable level (p < 0.05). This study demonstrates that HT and pyrolysis (≥400 °C) are promising methods for treating VFR and detoxifying it, and the treated products are safe for further reutilization.

An overview of the occurrence, impact of process parameters, and the fate of antibiotic resistance genes during anaerobic digestion processes

Antibiotic resistance genes (ARGs) have emerged as a significant global health threat, contributing to fatalities worldwide. Wastewater treatment plants (WWTPs) and livestock farms serve as primary reservoirs for these genes due to the limited efficacy of existing treatment methods and microbial adaptation to environmental stressors. Anaerobic digestion (AD) stands as a prevalent biological treatment for managing sewage sludge and manure in these settings. Given the agricultural utility of AD digestate as biofertilizers, understanding ARGs' fate within AD processes is essential to devise effective mitigation strategies. However, understanding the impact of various factors on ARGs occurrence, dissemination, and fate remains limited. This review article explores various AD treatment parameters and correlates to various resistance mechanisms and hotspots of ARGs in the environment. It further evaluates the dissemination and occurrence of ARGs in AD feedstocks and provides a comprehensive understanding of the fate of ARGs in AD systems. This review explores the influence of key AD parameters such as feedstock properties, pretreatments, additives, and operational strategies on ARGs. Results show that properties such as high solid content and optimum co-digestion ratios can enhance ARG removal, while the presence of heavy metals, microplastics, and antibiotics could elevate ARG abundance. Also, operational enhancements, such as employing two-stage digestion, have shown promise in improving ARG removal. However, certain pretreatment methods, like thermal hydrolysis, may exhibit a rebounding effect on ARG levels. Overall, this review systematically addresses current challenges and offers future perspectives associated with the fate of ARGs in AD systems.

Potential of combined reactor and static composting applications for the removal of heavy metals and antibiotic resistance genes from chicken manure

Chicken manure (CM) can pose a serious threat to environmental and human health, and need to be managed properly. The compost can effectively treat CM. However, there is limited research on the heavy metals and antibiotic resistance genes (ARGs) during compost CM. In this study, the combined application of reactor and static composting (RSC) was used to produce organic fertilizer of CM (OCM), and heavy metals, ARGs and bacterial community structure was investigated. The results show that RSC could be used to produce OCM, and OCM meet the National organic fertilizer standard (NY/T525-2021). Compared to the initial CM, DTPA-Cu, DTPA-Zn, DTPA-Pb, DTPA-Cr, DTPA-Ni and DTPA-As in OCM decreased by 40.83%, 23.73%, 34.27%, 38.62%, 16.26%, and 43.35%, respectively. RSC decreased the relative abundance of ARGs in CM by 84.06%, while the relative abundance of sul1 and ermC increased. In addition, the relative abundance and diversity of ARGs were mainly influenced by the bacterial community, with Actinobacteria, Firmicutes, and Proteobacteria becoming the dominant phyla during composting, and probably being the main carriers and dispersers of most of the ARGs. Network analyses confirmed that Gracilibacillus, Lactobacillus, Nocardiopsis, Mesorhizobium and Salinicoccus were the main potential hosts of ARGs, with the main potential hosts of sul1 and ermC being Mesorhizobium and Salinicoccus. The passivation and physicochemical properties of heavy metals contribute to the removal of ARGs, with sul1 and ermC being affected by the toal heavy metals. Application of RSC allows CM to produce mature, safe organic fertilizer after 32 d and reduces the risk of rebound from ARGs, but the issues of sul1 and ermC gene removal cannot be ignored.

A systematic review of antibiotic resistance driven by metal-based nanoparticles: Mechanisms and a call for risk mitigation

Elevations in antibiotic resistance genes (ARGs) are due not only to the antibiotic burden, but also to numerous environmental pressures (e.g., pesticides, metal ions, or psychotropic pharmaceuticals), which have led to an international public health emergency. Metal-based nanoparticles (MNPs) poison bacteria while propelling nanoresistance at ambient or sub-lethal concentrations, acting as a wide spectrum germicidal agent. Awareness of MNPs driven antibiotic resistance has created a surge of investigation into the molecule mechanisms of evolving and spreading environmental antibiotic resistome. Co-occurrence of MNPs resistance and antibiotic resistance emerge in environmental pathogens and benign microbes may entail a crucial outcome for human health. In this review we expound on the systematic mechanism of ARGs proliferation under the stress of MNPs, including reactive oxygen species (ROS) induced mutation, horizontal gene transfer (HGT) relevant genes regulation, nano-property, quorum sensing, and biofilm formation and highlighting on the momentous contribution of nanoparticle released ion. As antibiotic resistance pattern alteration is closely knit with the mediate activation of nanoparticle in water, soil, manure, or sludge habitats, we have proposed a virulence and evolution based antibiotic resistance risk assessment strategy for MNP contaminated areas and discussed practicable approaches that call for risk management in critical environmental compartments.

Biochar induces different responses of intracellular and extracellular antibiotic resistance genes and suppresses horizontal transfer during lincomycin fermentation dregs composting

This study aims to indicate the influence of biochar on extracellular and intracellular ARGs (e/iARGs) variation and proliferation during lincomycin fermentation dregs (LFDs) compost. Biochar addition made iARGs keep reducing but eARGs increase to the maximum at the middle thermophilic phase and reduce at the end of the compost. Compared to control 3.15-log and 5.42-log reduction of iARGs and eARGs were observed, respectively. Biochar addition, bacterial community, and MGEs were the major contributors to iARGs and eARGs removal, with the contribution percentages of 38.4%, 31.0%, 23.7%, and 27.2%, 29.1%, and 34.9%, respectively. Moreover, biochar significantly inhibited eARGs transformation and RP4 plasmid conjugative transfer among E. coli DH5α and Pseudomonas aeruginosa HLS-6. The underlying mechanism involved in broken cell membranes of bacteria, and altered expression of oxidative stress genes and save our souls (SOS) response-related genes. The results indicated that biochar addition in composting could limit the dissemination of ARGs.

Alkaline etched hydrochar-based magnetic adsorbents produced from pharmaceutical industry waste for organic dye removal

A large amount of pharmaceutical industry waste (PIW) was inevitably produced every year, and the PIW can be degraded by high temperature reaction to form porous structures. The study proposed an innovative pathway to valorize PIW with hydrothermal carbonization (HTC) coupled with alkali etching (AE). Without adding any additives, magnetic hydrochar could be generated with rough surface topography and suitable specific surface area (S_BET) by this method. Effects of HTC conditions and alkaline solution concentrations on the physicochemical and adsorption properties of PIW were investigated, and adsorption mechanism was explored. Based on evaluations of the magnetism, cyclic regeneration, and heavy metal leaching properties of the products, the feasibility of preparing magnetic adsorbents with solid waste by HTC coupled AE was established. The alkaline etching pharmaceutical industry waste (AEPIW) hydrochar showed the highest S_BET (54.64 m²/g) after the PIW was treated by 260 °C for 2 h plus 1 mol/L KOH. The removal rate of methylene blue (MB) could exceed 90% and the saturated magnetization was ~8 emu/g. The proposed new method was able to convert the low-value solid industrial waste into high-performance hydrochar-based magnetic adsorbents, which was tested to have a capability to efficiently and sustainably remove organic pollutants from water.

Pyrolysis of Ca/Fe-rich antibiotic fermentation residues into biochars for efficient phosphate removal/recovery from wastewater: Turning hazardous waste to phosphorous fertilizer

Ca/Fe-rich antibiotic fermentation residues (AFRs), a type of hazardous waste, can be regarded as recyclable biomass and metal resources. However, concurrent detoxification and reutilization of biomass and metals resources from AFRs have never been reported before. In this study, Ca/Fe-rich vancomycin fermentation residues were pyrolyzed into biochar to adsorb phosphate for the first time. The residual vancomycin and antibiotic resistance genes were completely decomposed during pyrolysis. The resultant Ca/Fe-rich biochar exhibited excellent performance at adsorbing phosphate without further modifications. The process had rapid kinetics and a maximum adsorption capacity of 102 mg P/g. Ca and Fe were the active sites, whereas different mechanisms were observed under acidic and alkaline conditions. Surprisingly, HCO₃^- enhanced phosphate adsorption with an increase of adsorption capacity from 43.9 to 71.0 mg/g when HCO₃^- concentration increased from 1 to 10 mM. Furthermore, actual wastewater could be effectively treated by the biochar. The phosphate-rich spent biochar significantly promoted seed germination (germination rate: 96.7 % vs. 80.0 % in control group, p < 0.01) and seedling growth (shoot length was increased by 57.9 %, p < 0.01) due to the slow release of bioavailable phosphate, and thus could be potentially used as a phosphorous fertilizer. Consequently, the hazardous waste was turned into phosphorous fertilizer, with the additional benefits of detoxifying AFRs, reutilizing biomass and metal resources from AFRs, controlling phosphate pollution, and recovering phosphate from wastewater.

Performance and mechanism of Pb2+ and Cd2+ ions’ adsorption via modified antibiotic residue-based hydrochar

This study investigated the hydrochar-based porous carbon prepared by combining the technical route of hydrothermal carbonization (HTC) + chemical activation. The hydrochar morphology was adjusted by changing the activation reaction conditions and adding metal salts. Experiments showed that the activation of KHCO₃ significantly increased the specific surface area and pore size of the hydrochar. Besides, oxygen-rich groups on the surface of the activated hydrochar interacted with heavy metal ions to achieve efficient adsorption. The activated hydrothermal carbon adsorption capacity for Pb²⁺ and Cd²⁺ ions reached 289 and 186 mg/g, respectively. The adsorption mechanism study indicated that the adsorption of Pb²⁺ and Cd²⁺ was related to electrostatic attraction, ion exchange, and complexation reactions. The "HTC + chemical activation" technology was environmentally friendly and effectively implemented antibiotic residues. Carbon materials with high adsorption capacity can be prepared so that biomass resources can be utilized with excessive value, as a consequence presenting technical assistance for the comprehensive disposal of organic waste in the pharmaceutical industry and establishing a green and clean production system.

Pyrolysis of antibiotic mycelial residue for biochar: Kinetic deconvolution, biochar properties, and heavy metal immobilization

The safe disposal of antibiotic mycelial residue (AMR), a hazardous waste, is a pressing problem owing to the spread of antibiotic and heavy metal pollution. In this study, AMR pyrolysis at different temperatures and heating rates was investigated to prepare valuable biochar for heavy metal immobilization. The results showed that AMR decomposition mainly involved three pseudo-reactions, with average activation energies of 252.4, 149.8, and 219.7 kJ/mol, that fitted a three-dimensional diffusion model. Increasing the pyrolysis temperature and heating rate decreased the yield and volatile matter content of biochar, but the ash content, fixed carbon content, and aromaticity increased. The AMR-derived biochar had a favorable fuel property (18.1-19.8 MJ/kg) and stability against degradation in soil. Calcium oxalate hydrate, a major mineral in AMR, degraded during biochar formation. Furthermore, high pyrolysis temperature promoted the residual fractions of Cr, Cu, Zn, Cd, and Pb in biochar, more so than did the heating rate, inducing a low potential ecological risk. In particular, the leaching rate of Zn decreased from 46.9% in AMR to 0.3% in biochar obtained at 700 °C with a heating rate of 10 °C/min. This study elucidates the formation process and physicochemical properties of AMR biochar, which helps in the harmless utilization of AMR as a carbon resource.

Biochar-amended composting of lincomycin fermentation dregs promoted microbial metabolism and reduced antibiotic resistance genes

Improper disposal of antibiotic fermentation dregs poses a risk of releasing antibiotics and antibiotic resistant bacteria to the environment. Therefore, this study evaluated the effects of biochar addition to lincomycin fermentation dregs (LFDs) composting. Biochar increased compost temperature and enhanced organic matter decomposition and residual antibiotics removal. Moreover, a 1.5- to 17.0-fold reduction in antibiotic resistance genes (ARGs) and mobile genetic elements (MGEs) was observed. Adding biochar also reduced the abundances of persistent ARGs hosts (e.g., Streptomyces, Pseudomonas) and ARG-related metabolic pathways and genes (e.g., ATP-binding cassette type-2 transport, signal transduction and multidrug efflux pump genes). By contrast, compost decomposition improved due to enhanced metabolism of carbohydrates and amino acids. Overall, adding biochar into LFDs compost reduced the proliferation of ARGs and enhanced microbial community metabolism. These results demonstrate that adding biochar to LFDs compost is a simple and efficient way to decrease risks associated with LFDs composting.

Hydrothermal treatment enhances the removal of antibiotic resistance genes, dewatering, and biogas production in antibiotic fermentation residues

Antibiotics and antibiotic resistance genes (ARGs) are enriched in antibiotic fermentation residues (AFRs). In this study, we investigated the effect of hydrothermal treatment on dewatering, biogas production, and removal of ARGs in the penicillin fermentation residue (PFR). Solid, 120 µm particles in the PFR were disintegrated to 30 - 40 µm after 140 - 180 °C hydrothermal range. Of extracellular polymeric substance, 79.8 ± 0.4% was decomposed to release 82.2 ± 0.6% of bound water at 180 °C. The effective solid-liquid separation was achieved only after a hydrothermal treatment of 180 °C. More than 75% of organic matter in the filtrate was transformed into biogas by the upflow anaerobic sludge blanket (UASB). The absolute abundance of 16 S rRNA and ARGs decreased by 2.4 - 5.2 logs after hydrothermal treatment. The ratio of extracellular ARGs (eARGs) to total ARGs increased at 80 °C and decreased at higher temperature (>120 °C). The absolute abundance of ARGs increased by 0.7 - 1.6 logs in anaerobic digestion, and the relative abundances of ARGs based on 16 S rRNA plummeted by 3 logs. Most (98.7 ± 0.4%) ARGs were distributed in suspended solids and were removed by membrane filtration. Hydrothermal treatment demonstrated broad applicability to 10 varieties of AFRs.

Effects of demineralization and devolatilization on fast pyrolysis behaviors and product characteristics of penicillin mycelial residues

In this study, the effects of demineralization and devolatilization methods including of water washing (WW), torrefaction (TF), washing-torrefaction (WT) and hydrothermal treatment (HT) on the fast pyrolysis characteristics of penicillin mycelial residues were studied. The materials and pyrolysis products were characterized by analysis methods including of thermogravimetric (TG), gas chromatograph (GC), gas chromatography-mass spectrometry (GC-MS), x-ray diffractometer (XRD), fourier transform-infrared spectroscopy (FT-IR) and x-ray photoelectron spectroscopy (XPS), etc. The results showed WW increased the yields of tar and decreased the yields of pyrolysis biochar due to the removal of alkali and alkaline earth metals (AAEMs), while TF and HT showed opposite results due the devolatilization. XPS and FT-IR results proved that the conversion from aliphatic C-(C, H) to aromatic groups C-O-C and CO was the key point for improving the aromatization of biochar. Pretreatments increased the relative proportions of N-containing heterocyclic compounds and phenolic compounds, reduced the proportions of O-containing heterocyclic compounds in pyrolysis tar. And TF and HT could eliminate the residual antibiotic and satisfy the principle of AMR harmless disposal.

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.

Combined hydrothermal treatment, pyrolysis, and anaerobic digestion for removal of antibiotic resistance genes and energy recovery from antibiotic fermentation residues

A process combining hydrothermal treatment (HT), pyrolysis, and anaerobic digestion can efficiently treat antibiotic fermentation residues (AFR). The process characteristics and antibiotic resistance genes (ARGs) removal efficiencies of each unit have been investigated. HT of 180 °C improved the biodegradability and dewaterability of the AFR. Pyrolysis of 500 °C and upflow anaerobic sludge blanket (UASB) of 6.5 ± 0.5 kg COD•(m³•d)^-1 recovered the organic matter in filter cake and filtrate of AFR. The biogas and pyrolysis gas can compensate the energy this system needs. HT of 180 °C could reduce 16S rRNA, ARGs, and mobile genetic elements (MGEs) by 2.3 to 7.4 logs. UASB increased the copy numbers of ARGs and MGEs, but the relative abundances of ARGs normalized against 16S rRNA were significantly declined. The ARGs and MGEs were enriched in suspended solids of digestate. The application of this process can promote the resources recycling of fermentation waste.

Multiple adsorption systems and electron-scale insights into the high efficiency coadsorption of a novel assembled cellulose via experiments and DFT calculations

In view of the characteristics of heavy metal and antibiotic compound pollution in the Pearl River Basin in Guangzhou. More scientifically modified cellulose, named HVUC, is characterized by multiple hydrophilic groups, long chains and large space and displays highly efficient adsorption of both Cd and sulfamethoxazole (SMZ) and good adaptability in a wide pH range and at high ion strength. Furthermore, the coadsorption mechanism was elaborated from multiple angles. Multiple adsorption experiments explained the competition and synergy effect in the adsorption process. The electrostatic potential maps indicated that HVUC had advantageous adsorption sites for both Cd and SMZ and that electrostatic interactions had the greatest impact on the adsorption of Cd and SMZ. The electron density and differential charge density images proved that Cd more easily overlapped electron clouds and transferred electrons with HVUC and that SMZ^- and could act as a bridge for SMZ^-. The equilibrium configuration indicated that the formation of Cd-SMZ^- complexes led to the bending and folding of SMZ^-, which was not conducive to overall adsorption when SMZ^- was close to HVUC and could lead to the release of SMZ^- when Cd was close to HVUC, which confirmed the proposed mechanism of complexation-decomplexation-complexation.

Effective removal of Cd2+, Zn2+ by immobilizing the non-absorbent active catalyst by packed bed column reactor for industrial wastewater treatment

Cadmium and zinc are leading heavy metal pollutants causing serious health problems when discharged into the aquatic environments. The present investigation focused on the bioaccumulation of Cd²⁺ and Zn²⁺depending on the sorption process by Bacillus amyloliquefaciens HM28. The selected bacterium was multi-metal (Zn²⁺, Pb²⁺, Cd²⁺, Cu²⁺ and Li⁺) and antibiotic (cefotaxime, ampicilin, nalidixic acid, ceftazidime, penicillin and kanamycin) resistance was resolved. The identified strain showed maximum resistance onCd²⁺ (2575 ppm) and Zn²⁺ (1300 ppm). The sorption of Cd²⁺ and Zn²⁺ by a dried bacterium was investigated. Biosorption of Cd²⁺ was maximum (98.4 ± 5.2%) at 100 mg/L concentration and maximum Zn²⁺ (98.3 ± 1.5%) was detected in the medium containing 150 mg/L metal ion. Bioremoval was maximum after 30 min contact time with dried biomass and the absorption rate improved. The optimum Cd²⁺ and Zn²⁺ bioremoval yield of 93 ± 4.4% and 89.8 ± 4.3% were observed, at pH 7.0 and 7.5, respectively. Despite the significant reduction in growth rate, heavy metals increased nitro-blue tetrazolium reduction from 11 ± 1.3 to 67 ± 3.3%. Dehydrogenase activity elevated due to heavy metal stress. Bacterial biomass was immobilized in a glass column (20 cm × 2 cm). Biosorption of Cd²⁺ and Zn²⁺ ions were performed in a packed bed column. The breakthrough time of Cd²⁺ was 210 min at 1 mL/min flow rate and it decreased 94 min at 5 mL/min flow rate, whereas 240 min at 1 mL/min, and 90 min at 5 mL/min, respectively. The absorption capacity was 4.87 ± 0.8 to 5.43 ± 0.5 mg/g for Cd²⁺ and 3.85 ± 0.3 to 4.53 ± 0.4 mg/g for Zn²⁺. The present findings revealed the potential of B. amyloliquefaciens HM28 biomass in Cd²⁺ and Zn²⁺ biosorption, with feasibility in the bioremediation of Cd²⁺ and Zn²⁺ contaminated water.

Direct use of the solid waste from oxytetracycline fermentation broth to construct Hf-containing catalysts for Meerwein-Ponndorf-Verley reactions

The oxytetracycline fermentation broth residue (OFR) is an abundant solid waste in the fermentation industry, which is hazardous but tricky to treat. The resource utilization of the waste OFR is still challenging. In this study, a novel route of using OFR was proposed that OFR was used as the organic ligands to construct a new hafnium based catalyst (Hf-OFR) for Meerwein–Ponndorf–Verley (MPV) reactions of biomass-derived platforms. The acidic groups in OFR were used to coordinate with Hf⁴⁺, and the carbon skeleton structures in OFR were used to form the spatial network structures of the Hf-OFR catalyst. The results showed that the synthesized Hf-OFR catalyst could catalyze the MPV reduction of various carbonyl compounds under relatively mild reaction conditions, with high conversions and yields. Besides, the Hf-OFR catalyst could be recycled at least 5 times with excellent stability in activity and structures. The prepared Hf-OFR catalyst possesses the advantages of high efficiency, a simple preparation process, and low cost in ligands. The proposed strategy of constructing catalysts using OFR may provide new routes for both valuable utilization of the OFR solid waste in the fermentation industry and the construction of efficient catalysts for biomass conversion.

An efficient Hf-OFR catalyst was designed in which Hf⁴⁺ interacts with oxygen-containing acidic groups in oxytetracycline fermentation broth residues for MPV reactions.

Enrichment of antibiotic resistance genes after sheep manure aerobic heap composting

In this study, physio-chemical properties, 45 antibiotics, 6 heavy metals, 42 antibiotic resistance genes (ARGs), 3 mobile genetic elements, and the bacterial community structure were investigated to analyze the fate of ARGs during sheep manure aerobic heap composting. Results showed that sheep manure heap composting could produce mature compost. The degradation processes reduced the total antibiotics content by 85%. The abundance of ARGs and mobile genetic elements (MGEs) were enriched 9-fold, with the major increases to sul and tet genes (sulI, sulII, tetQ, and tetX). Tetracycline and sulfonamide resistance genes were the most abundant ARGs after composting (more than 88% of all genes). The genes tetA, tetX and sulI were related to the most diverse bacteria that were most able to proliferate during heap composting. Therefore, sulI and tetX are the major ARGs to be controlled, and Actinobacteria and Bacteroidetes may be the major host bacteria.

Discarded antibiotic mycelial residues derived nitrogen-doped porous carbon for electrochemical energy storage and simultaneous reduction of antibiotic resistance genes(ARGs)

The question of how to reasonably dispose and recycle antibiotic mycelial residues (AMRs), a hazardous waste, is a critical issue. The AMRs containing nitrogen-rich organic matters shows a promising alternative feedstock of nitrogen-doped porous carbons (NPCs). Here, the NPCs with the ultrahigh surface area (2574.9 m² g^-1) were prepared by using the discarded oxytetracycline mycelial residues (OMRs) and further used as an electrode for supercapacitor. A series of experiments including scanning/transmission electron microscope, Brunauer-Emmett-Teller measurement, and electrochemical impedance spectrum revealed that the NPC-2-900 exhibited a high N content, large surface area, and high electrical conductivity. The electrochemical performance of the NPC was tested by cyclic voltammetry, galvanostatic charge/discharge cycling, and rate capability test. The optimized NPC-2-900 displayed distinguish specific capacitance (307 F g^-1), cycling stability (over 95% capacitance retention after 2000 cycles even at a high current density of 20 A g^-1) and superior rate performance. Of particular interest, the qPCR test indicates the ARGs were reduced in the conversion process from OMRs to NPCs.

Alkaline-thermal pretreatment of spectinomycin mycelial residues: Insights on anaerobic biodegradability and the fate of antibiotic resistance genes

Alkaline-thermal (AT) pretreatment is an economical and efficient pretreatment method to improve anaerobic biodegradability of biowaste. This study investigated the effect of AT pretreatment of spectinomycin mycelial residues (SMRs) for promoting anaerobic biodegradability along with the reduction of antibiotic resistance genes (ARGs), and thus obtained the optimal conditions of AT pretreatment. Biomethane potential (BMP) test was conducted to evaluate the anaerobic biodegradability of untreated and pretreated SMRs, and the fate of ARGs was tracked by quantitative polymerase chain reaction. Results showed that the modified Gompertz model fitted the results of BMP tests satisfactorily. Furthermore, AT pretreatment promoted BMP (B₀) and reduced lag phase (λ) effectively. These were attributed to the solubilization of SMRs. The analyses of the changes in dissolved organic matter indicated that AT pretreatment could facilitate the solubilization of both biodegradable (e.g. protein) and recalcitrant matter (e.g. humic-like, analyzing by EEMs-PARAFAC), which had a significant corresponding positive (Person correlation, p < 0.01) and negative (Partial correlation, p < 0.01) influences on anaerobic biodegradability. However, the positive effects surpassed the negative effects, promoting the overall anaerobic biodegradability of SMRs. In addition, a considerable reduction of ARGs (by 0.62-1.36 log units) was observed at pH ≥ 12, attributed to the hydrolysis of phosphodiester bond of DNA in strong alkaline solution. Considering both anaerobic biodegradability and ARGs, the optimal AT condition was concluded as pH 12, temperature 90 °C and time 120 min.

Impacts of Cu and Zn on the performance, microbial community dynamics and resistance genes variations during mesophilic and thermophilic anaerobic digestion of swine manure

In this work, fate of antibiotic resistance genes (ARGs), heavy metal resistance genes (MRGs) and intI1 were investigated during mesophilic (mAD) and thermophilic anaerobic digestion (tAD) of swine manure with presence of Cu and Zn. Results showed that metal reduced the lag phase time. Cu showed stronger inhibition than Zn on archaea community and metals inhibited the growth of acetoclastic methanogens during mAD. Although total concentration of metals increased after AD, they were transformed into stable state. The abundance of qnrS, sul1, sul2 and drfA7 increased 1.2-5.7 times after mAD, while reduced after tAD, showed that tAD was effective in ARGs removal. Structural equation model analysis suggested that intI1 had the most standardized direct effects on ARGs variation in mAD (R = 0.85, p < 0.01), while the co-occurrence of MRGs with ARGs showed significantly positive influences on ARGs variation in tAD (R = 0.82, p < 0.01).

The release of organic matter, nitrogen, phosphorus and heavy metals from erythromycin fermentation residue under heat-activated persulfate oxidation conditioning

Erythromycin fermentation residue (EFR) is one kind of biological waste with high organic matter content. The recycling of EFR is not only beneficial to the environmental protection, but also to the economic development. In this study, the release of organic matter, nitrogen (N), phosphorus (P) and heavy metals (HMs) from EFR under heat-activated persulfate (PS) oxidation conditioning was investigated. Results indicated that oxidation conditioning promoted the release of soluble chemical oxygen demand (SCOD). Heat-activated PS oxidation conditioning boosted the release of total nitrogen (TN), ammonia‑nitrogen (NH₄⁺-N) and nitrate‑nitrogen (NO₃^--N) into the supernatant, as well as the decomposition of organic nitrogen (ON). Concurrently, heat-activated PS oxidation conditioning facilitated the release of total phosphorus (TP), orthophosphate (PO₄^3--P) and organic phosphorus (OP) into the supernatant, and the decomposition of OP. Furthermore, heat-activated PS oxidation conditioning resulted in the increase of release efficiencies of HMs. Therefore, heat-activated PS oxidation conditioning was beneficial to the release of organic matter, nutrients and HMs.

Dosage effects of lincomycin mycelial residues on lincomycin resistance genes and soil microbial communities

Lincomycin mycelial residues (LMRs) are one kind of byproduct of the pharmaceutical industry. Hydrothermal treatment has been used to dispose of them and land application is an attractive way to reuse the treated LMRs. However, the safe dose for soil amendment remains unclear. In this study, a lab-scale incubation experiment was conducted to investigate the influence of the amendment dosage on lincomycin resistance genes and soil bacterial communities via quantitative PCR and 16S rRNA sequencing. The results showed that introduced lincomycin degraded quickly in soil and became undetectable after 50 days. Degradation rate of the high amendment amount (100 mg kg^-1) was almost 4 times faster than that of low amendment amount (10 mg kg^-1). Moreover, the introduced LMRs induced the increase of lincomycin resistance genes after incubation for 8 days, and two genes (lmrA and lnuB) showed a dosage-related increase. For example, the abundance of gene lmrA was 17.78, 74.13 and 128.82 copies g^-1 soil for lincomycin concentration of 10, 50 and 100 mg kg^-1, respectively. However, the abundance of lincomycin resistance genes recovered to the control level as the incubation period extended to 50 days, indicating a low persistence in soil. In addition, LMRs application markedly shifted the bacterial composition and significant difference was found between control soil, 10 mg kg^-1 and 50 mg kg^-1 lincomycin amended soil. Actually, several genera bacteria were significantly related to the elevation of lincomycin resistance genes. These results provided a comprehensive understanding of the effects of lincomycin dosage on the fate of resistance genes and microbial communities in LMRs applied soil.