Dynamics of antibiotics and antibiotic resistance genes in four types of kitchen waste composting processes

Exploring product maturation, microbial communities and antibiotic resistance gene abundances during food waste and cattle manure co-composting

This study proposed combining food waste (FW) and cattle manure (CM) in composting to improve the product maturity. The findings suggested that the inclusion of CM effectively extended the thermophilic stage, facilitated the decomposition of cellulose, and enhanced the production of humus-like substances by enhancing beneficial microbial cooperation. Adding 40 % CW was optimal to reduce the nitrogen loss, increase the cellulose degradation rate to 22.07 %, increase germination index (GI) to 140 %, and reduce normalized antibiotic resistance gene (ARG) abundances. Adding CW could promote the transformation of protein-like compounds, thereby enhancing the humification process of organic substances. Structural equation modeling further verified that the temperature was the key factor affecting humification production, while the main driver for ARGs was physiochemical parameters. This study shows that co-composting of FW and CM offers the potential to promote humification, reduce ARG abundance, and improve fertilizer quality for utilization of both biowastes in the field.

Efficient elimination of antibiotics and antibiotic resistance genes in hyperthermophilic sludge composting

Composting is widely applied in recycling ever-increasing sewage sludge. However, the insufficient elimination of antibiotics and antibiotic resistance genes (ARGs) in conventional compost fertilizer poses considerable threat to agriculture safety and human health. Here we investigated the efficacy and potential mechanisms in the removal of antibiotics and ARGs from sludge in hyperthermophilic composting (HTC) plant. Our results demonstrated that the HTC product was of high maturity. HTC led to complete elimination of antibiotics and potential pathogens, as well as removal of 98.8 % of ARGs and 88.1 % of mobile genetic elements (MGEs). The enrichment of antibiotic-degrading candidates and related metabolic functions during HTC suggested that biodegradation played a crucial role in antibiotic removal. Redundancy analysis (RDA) and structural equation modelling (SEM) revealed that the reduction of ARGs was attributed to the decline of ARG-associated bacteria, mainly due to the high-temperature selection. These findings highlight the feasibility of HTC in sludge recycling and provide a deeper understanding of its mechanism in simultaneous removal of antibiotics and ARGs.

Risk level and removal performance of antibiotic resistance genes and bacterial pathogens in static composting with different temperatures

The effect of different levels of temperature on resistance genes is not clear in mesophilic static composting (<50 °C). This study conducted livestock manure composting with different temperature gradients from 20 to 50 °C, it was found that the reduction rates of risk rank-I antibiotic resistance genes (from 3 % to 66 %), metal resistance genes (from -50 % to 76 %) and bacterial pathogens (from 72 % to 91 %) all increased significantly with increasing temperature from 20 to 50°C. The vulnerability of bacterial communities increased significantly, and the assembly process of bacterial communities changed from deterministic to stochastic with the increase of composting temperature. Higher temperature could accelerate the removal of thermolabile resistance genes hosts or pathogenic hosts carrying mobile genetic elements by directly or indirectly affecting organic acids content. Therefore, for soil safety, the temperature of the manure recycling process should be increased as much as possible.

Study on the biodegradation characteristics and mechanism of tetracycline by Serratia entomophila TC-1

Microbial degradation is an important solution for antibiotic pollution in livestock and poultry farming wastes. This study reports the isolation and identification of the novel bacterial strain Serratia entomophila TC-1, which can degrade 87.8 % of 200 mg/L tetracycline (TC) at 35 °C, pH 6.0, and an inoculation amount of 1 % (v/v). Based on the intermediate products, a possible biological transformation pathway was proposed, including dehydration, oxidation ring opening, decarbonylation, and deamination. Using Escherichia coli and Bacillus subtilis as biological indicators, TC degraded metabolites have shown low toxicity. Whole-genome sequencing showed that the TC-1 strain contained tet (d) and tet (34), which resist TC through multiple mechanisms. In addition, upon TC exposure, TC-1 participated in catalytic and energy supply activities by regulating gene expression, thereby playing a role in TC detoxification. We found that TC-1 showed less interference with changes in the bacterial community in swine wastewater. Thus, TC-1 provided new insights into the mechanisms responsible for TC biodegradation and can be used for TC pollution treatment.

Evolution of the Black solider fly larvae gut antibiotic resistome during kitchen waste disposal

Kitchen waste (KW) is an important reservoir of antibiotic resistance genes (ARGs). Black solider fly larvae (BSFL) are extensively employed in KW disposal, closely linking to their robust gut microbes. However, antibiotic resistome in BSFL gut during the KW disposal processes and the mechanism remain unclear. In the present study, the antibiotic resistome in BSFL gut within the 12 days KW disposal processes were investigated. Results showed that, ARGs abundance initially increased and subsequently decreased, the five most prevalent core ARG classes were tetracycline, aminoglycoside, cephalosporin, lincosamide and multidrug. A total of 7 MGE types were observed and the horizontal gene transfer (HGT) of ARGs was predominantly mediated by plasmids. Host microbes were mainly categorized into Proteobacteria (98.12 %) and their assemblies were mainly classified into the deterministic processes. To elucidate the driving mechanisms, the mantel test and the structural equation model (SEM) were developed. Results indicated that microbial functions (0.912, p < 0.0001) and microbial community (1.014, p = 0.036), consistently showed very significant relationships with the patterns of ARGs, which presented higher direct effects than indirect effects. Overall, this study makes an initial contribution to a more deepgoing comprehension of the gut antibiotic resistome of BSFL during KW disposal.

Design and fabrication of acorn-like Janus molecularly imprinted materials for highly specific separation and enrichment of oxytetracycline from restaurant oily wastewater

Molecularly imprinted polymer (MIP) is dedicated to the adsorption of target substances in the aqueous phase, but ignores the adsorption in a more complex environment (oily wastewater). In order to explore the application field of existing MIPs, acorn-like Janus particles were fabricated by photo-initiated seed swelling polymerization. A novel amphiphilic Janus-MIP was prepared with the acorn-like Janus particles as matrix, methacrylic acid, ethylene dimethacrylate and oxytetracycline (OTC) as functional monomers, crosslinking agents and template molecules via surface initiated-atom transfer radical polymerization (SI-ATRP). For comparison, the poly (glycidyl methacrylate-co-ethylene glycol dimethacrylate) (poly (GMA-co-EDMA)) microspheres were also utilized as the matrix to prepare common spherical-MIP. The adsorption capacity of Janus-MIP for OTC was 23.8 mg g-1 in oil-water system, while the adsorption capacity of spherical-MIP for OTC was only 12.6 mg g-1 in the same system. At the same time, through high performance liquid chromatography (HPLC) analysis, Janus-MIP can specifically recognize and adsorb trace OTC in restaurant oily wastewater samples, and the proposed method exhibited a lower limit of detection (LOD, 3 ng mL-1) and a higher OTC recovery rate (94.2 %-98.4 %). This work demonstrated great potential for the detection and control of OTC contamination from real samples in an oil-water mixed environment.

The role of cattle manure-driven polysaccharide precursors in humus formation during composting of spent mushroom substrate

The study examined the impact of adding cattle manure to the composting process of Agaricus bisporus mushroom substrate on compost humification. A control group CK comprised entirely of Agaricus bisporus mushroom substrate, while the experimental group CD (70 percent Agaricus bisporus mushroom substrate and 30 percent cattle manure) comprised the two composting treatments that were established. The study determined that the addition of cow dung has promoted the formation of humus components. Particularly, humic substance (HS-C) and humic acid (HA) increased by 41.3 and 74.7%, respectively, and the ratio of humic acid to fulvic acid (HA/FA) also increased by 2.78. It showed that the addition of cow dung accelerated the synthesis and decomposition of precursors, such as polysaccharides, polyphenols, and reducing sugars. Thereby promoting the formation of humic acid. Network analysis revealed that adding cow dung promoted microbial interactions increased the complexity and stability of the bacterial and fungal symbiotic network, enhanced cooperation and reciprocity among microbes, and assisted in transforming fulvic acid (FA) components. Structural equation modeling (SEM) is a multivariate data analysis method for analyzing complex relationships among constructs and core indicators. SEM illustrated that introducing cattle manure into the composting process resulted in alterations to the correlation between physicochemical parameters and the microbial community, in addition to humus formation. Polysaccharides are the primary precursors for polymerization to form HA, which is an essential prerequisite for the conversion of fulvic acid to humic acid. Additionally, microbes affected the formation of humus, with bacteria substantially more influential than fungi. These findings provide new ideas for regulating the degree of humification in the composting process and have important practical implications for optimizing mushroom cultivation and composting techniques today.

Synergistic removal of total petroleum hydrocarbons and antibiotic resistance genes in Yellow River Delta wetlands contaminated soil composting regulated by biogas slurry addition

The interactive effects between the emerging contaminant antibiotic resistance genes (ARGs) and the traditional pollutant total petroleum hydrocarbons (TPHs) in contaminated soils remain unclear. The synergistic removal of TPHs and ARGs from composted contaminated soil, along with the microbial mechanisms driven by the addition of biogas slurry, have not yet been investigated. This study explored the impact of biogas slurry on the synergistic degradation mechanisms and bacterial community dynamics of ARGs and TPHs in compost derived from contaminated soil. The addition of biogas slurry resulted in a reduction of targeted ARGs and mobile genetic elements (MGEs) by 9.96%-95.70% and 13.32%-97.66%, respectively. Biogas slurry changed the succession of bacterial communities during composting, thereby reducing the transmission risk of ARGs. Pseudomonas, Cellvibrio, and Devosia were identified as core microorganisms in the synergistic degradation of ARGs and TPHs. According to the partial least squares path model, temperature and NO3- indirectly influenced the removal of ARGs and TPHs by directly regulating the abundance and composition of host microbes and MGEs. In summary, the results of this study contribute to the high-value utilization of biogas slurry and provide methodological support for the low-cost remediation of contaminated soils.

Polyethylene and sulfa antibiotic remediation in soil using a multifunctional degrading bacterium

To obtain a multifunctional bacterium that can effectively degrade polyethylene (PE) and sulfonamide antibiotics (SAs), PE and SAs were selected as the primary research objects. Multifunctional degrading bacteria were isolated and screened from an environment in which plastics and antibiotics have existed for a long time. An efficient degrading strain, Raoultella sp., was screened by measuring the degradation performance of PE and SAs. We analyzed the changes in the microbial community of indigenous bacteria using 16S rRNA. After 60 d of degradation at 28 °C, the Raoultella strain to PE degradation rate was 4.20 %. The SA degradation rates were 96 % (sulfonathiazole, (ST)), 86 % (sulfamerazine, (SM)), 72 % (sulfamethazine, (SM2)) and 64 % (sulfamethoxazole, (SMX)), respectively. This bacterium increases the surface roughness of PE plastic films and produces numerous gullies, pits, and folds. In addition, after 60 d, the contact angle of the plastic film decreased from 92.965° to 70.205°, indicating a decrease in hydrophobicity. High-throughput sequencing analysis of the degrading bacteria revealed that the Raoultella strain encodes enzymes involved in PE and SA degradation. The results of this study not only provide a theoretical basis for further study of the degradation mechanism of multifunctional and efficient degrading bacteria but also provide potential strain resources for the biodegradation of waste plastics and antibiotics in the environment.

Seasonal variations of airborne microbial diversity in waste transfer stations and preventive effect on Streptococcus pneumoniae induced pulmonary inflammation

Environment, location, and season are important factors that influence the microbiological community, yet, little research on airborne microorganisms in waste transfer stations (WTSs). Here, the airborne bacterial and fungal communities at four WTSs during different seasons were analyzed by high-throughput sequencing. The bacteria were isolated by cultural method and screened bacterium alleviate inflammation induced by Streptococcus pneumoniae (Spn) by regulating gut microbiome. The results revealed that collected bioaerosols from the WTSs varied significantly by location and season. Proteobacteria and Pseudomonadota are prevalent in summer and winter, respectively. Ascomycota was predominant in two seasons. Hazard quotients for adults from four WTSs were below one. Three selected potential probiotics were formulated into a microbial preparation with a carrier that effectively prevented inflammation in bacterial and animal experiments. The expression levels of interleukin-1β, interleukin-6, and tumor necrosis factor-α in Pre group (0.11, 0.17, and 0.48-fold) were significantly lower than Spn group (2.75, 1.71, and 5.01-fold). These mechanisms are associated with changes in gut microbiota composition and short-chain fatty acids (SCFAs) levels, such as affecting Lachnospiraceae lachnospira abundance and acetic acid content. This study provides insights into the potential application of probiotics derived from WTSs as an alternative approach to preventing respiratory infections.

Antibiotics and antibiotic resistance gene dynamics in the composting of antibiotic fermentation waste - A review

Fate of antibiotics and antibiotic resistance genes (ARGs) during composting of antibiotic fermentation waste (AFW) is a major concern. This review article focuses on recent literature published on this subject. The key findings are that antibiotics can be removed effectively during AFW composting, with higher temperatures, appropriate bulking agents, and suitable pretreatments improving their degradation. ARGs dynamics during composting are related to bacteria and mobile genetic elements (MGEs). Higher temperatures, suitable bulking agents and an appropriate C/N ratio (30:1) lead to more efficient removal of ARGs/MGEs by shaping the bacterial composition. Keeping materials dry (moisture less than 30%) and maintaining pH stable around 7.5 after composting could inhibit the rebound of ARGs. Overall, safer utilization of AFW can be realized by optimizing composting conditions. However, further removal of antibiotics and ARGs at low levels, degradation mechanism of antibiotics, and spread mechanism of ARGs during AFW composting require further investigation.

Microbiome data analysis via machine learning models: Exploring vital players to optimize kitchen waste composting system

Composting, reliant on microorganisms, effectively treats kitchen waste. However, it is difficult to precisely understand the specific role of key microorganisms in the composting process by relying solely on experimental research. This study aims to employ machine learning models to explore key microbial genera and to optimize composting systems. After introducing a novel microbiome preprocessing approach, Stacking models were constructed (R2 is about 0.8). The SHAP method (SHapley Additive exPlanations) identified Bacillus, Acinetobacter, Thermobacillus, Pseudomonas, Psychrobacter, and Thermobifida as prominent microbial genera (Shapley values ranging from 3.84 to 1.24). Additionally, microbial agents were prepared to target the identified key genera, and experiments demonstrated that the composting quality score was 76.06 for the treatment and 70.96 for the control. The exogenous agents enhanced decomposition and improved compost quality in later stages. In summary, this study opens up a new avenue to identifying key microorganisms and optimizing the biological treatment process.

Batch-fed composting of food waste: Microbial diversity characterization and removal of antibiotic resistance genes

The aim of this work was to study the impact of batch-fed strategies on bacterial communities and ARGs in compost. The findings demonstrate that batch-feeding helped maintain high temperatures in the compost pile for an extended period (above 50 °C for 18 days), which in turn facilitated water dissipation. High-throughput sequencing showed that Firmicutes played a significant role in batch-fed composting (BFC). They had a high relative abundance at the beginning (98.64%) and end (45.71%) of compost. Additionally, BFC showed promising results in removing ARGs, with reductions of 3.04-1.09 log copies/g for Aminoglycoside and 2.26-2.44 log copies/g for β_Lactamase. This study provides a comprehensive survey of BFC and demonstrates its potential for eliminating resistance contamination in compost.

Microbial inoculants enhance the persistence of antibiotic resistance genes in aerobic compost of food waste mainly by altering interspecific relationships

The effects of microbial inoculants on ARG removal in composting are poorly understood. Here, a co-composting method for food waste and sawdust amended with different microbial agents (MAs) was designed. The results show that the compost without MA unexpectedly achieved the best ARG removal. The addition of MAs markedly increased the abundance of tet, sul and multidrug resistance genes (p < 0.05). Structural equation modeling demonstrated that MAs can enhance the contribution of the microbial community to ARG changes by reshaping community structure and altering the ecological niche, causing the proliferation of individual ARGs, an effect related to the MA component. Network analysis revealed that inoculants weakened the correlation between ARGs and community but increased the linkage between ARGs and core species, suggesting that inoculant-induced ARG proliferation may correspond with gene exchange occurring mainly between core species. The outcome provides new insights into MA application for ARG removal in waste treatment.

Antibiotic resistome associated with influencing factors in industrial-scale organic waste aerobic composting plants

This study investigated the fate of antibiotic resistance genes (ARGs) and bacterial evolution in six industrial-scale organic wastes aerobic composting plants and identified key factors driving ARGs dynamics. A total of 226 ARGs and 46 mobile genetic elements (MGEs), mainly resistant to aminoglycoside and MLSB, were detected by high-throughput qPCR. Briefly, aerobic composting showed good performance in reducing the diversity and abundance of ARGs, where the total absolute abundance was reduced by 88.34%-97.08% except for cattle manures. Rapid composting may lead to a rebound of ARGs due to long-term storage compared to traditional composting. Hub ARGs and bacterial genera were screened out by co-occurrence patterns. As the dominant phyla in composting, the main potential hosts of ARGs were Firmicutes, Bacteroidota and Proteobacteria. Structural equation model indicated that MGEs and heavy metals were key factors affecting ARGs dynamics. In addition, nutrients and bacterial α-diversity can indirectly influence ARGs by affecting MGEs.

Impacts of garbage classification and disposal on the occurrence of pharmaceutical and personal care products in municipal solid waste leachates: A case study in Shanghai

Leachate generated during the treatment and disposal of municipal solid wastes (MSWs) can be an important source of pharmaceutical and personal care products (PPCPs) in the environment. With the implementation of garbage classification policy in China, the disposal methods of MSWs have changed, while its impacts on the occurrence of PPCPs in the generated leachate remain unknown. In this study, we investigated 49 target PPCPs in the leachates of classified MSWs, i.e. residual waste leachate (RWL) and food waste leachate (FWL), and revealed the influence of garbage classification implementation on the occurrence of PPCPs in leachates to be treated. The results showed the concentration and mass load of target PPCPs in the RWL samples (median values: 34.9 ng/L and 52.3 mg/d, respectively) were significantly higher than those in the FWL samples (median values: 19.3 ng/L and 14.5 mg/d, respectively). Macrolide (ML) antibiotics were the predominant PPCPs in the RWL samples, while in the FWL samples, quinolone (QL) antibiotics exhibited the highest concentration and mass load. The implementation of garbage classification policy led to the reduction of PPCP mass load (from 739 g/d to 262 g/d) in leachates to be treated. The findings are helpful for better designing or managing MSW treatment and disposal processes to minimize the emission of PPCPs from MSW leachates.

Reductions in abundances of intracellular and extracellular antibiotic resistance genes by SiO2 nanoparticles during composting driven by mobile genetic elements

Applying exogenous additives during the aerobic composting of livestock manure is effective for slowing down the spread of antibiotic resistance genes (ARGs) in the environment. Nanomaterials have received much attention because only low amounts need to be added and they have a high capacity for adsorbing pollutants. Intracellular ARGs (i-ARGs) and extracellular ARGs (e-ARGs) comprise the resistome in livestock manure but the effects of nanomaterials on the fates of these different fractions during composting are still unclear. Thus, we investigated the effects of adding SiO₂ nanoparticles (SiO₂NPs) at four levels (0 (CK), 0.5 (L), 1 (M), and 2 g/kg (H)) on i-ARGs, e-ARGs, and the bacterial community during composting. The results showed that i-ARGs represented the main fraction of ARGs during aerobic composting of swine manure, and their abundance was lowest under M. Compared with CK, M increased the removal rates of i-ARGs and e-ARGs by 17.9% and 100%, respectively. SiO₂NPs enhanced the competition between ARGs hosts and non-hosts. M optimized the bacterial community by reducing the abundances of co-hosts (Clostridium_sensu_stricto_1, Terrisporobacter, and Turicibacter) of i-ARGs and e-ARGs (by 96.0% and 99.3%, respectively) and killing 49.9% of antibiotic-resistant bacteria. Horizontal gene transfer dominated by mobile genetic elements (MGEs) played a key role in the changes in the abundances of ARGs. i-intI1 and e-Tn916/1545 were key MGEs related closely to ARGs, and the maximum decreases of 52.8% and 100%, respectively, occurred under M, which mainly explained the decreased abundances of i-ARGs and e-ARGs. Our findings provide new insights into the distribution and main drivers of i-ARGs and e-ARGs, as well as demonstrating the possibility of adding 1 g/kg SiO₂NPs to reduce the propagation of ARGs.

Effect of bioaugmentation on tetracyclines influenced chicken manure composting and antibiotics resistance

Antibiotic residue in husbandry waste has become a serious concern. In this study, contaminated chicken manure composting was conducted to reveal the bioaugmentation effect on tetracyclines residue and antibiotics resistance genes (ARGs). The bioaugmented composting removed most of the antibiotics in 7 days. Under bioaugmentation, 96.88 % of tetracycline and 92.31 % of oxytetracycline were removed, 6.32 % and 20.93 % higher than the control (P < 0.05). The high-temperature period was the most effective phase for eliminating antibiotics. The treatment showed a long high-temperature period (7 days), while no high-temperature period was in control. After composting, the treatment showed 13.87 % higher TN (26.51 g/kg) and 13.42 % higher NO₃^--N (2.45 g/kg) than control (23.28 and 2.16 g/kg, respectively) but 12.72 % lower C/N, indicating fast decomposition and less nutrient loss. Exogenous microorganisms from bioaugmentation significantly reshaped the microbial community structure and facilitated the enrichment of genera such as Truepera and Fermentimonas, whose abundance increased by 71.10 % and 75.37 % than the control, respectively. Remarkably, ARGs, including tetC, tetG, and tetW, were enhanced by 198.77 %, 846.77 %, and 62.63 % compared with the control, while the integron gene (intl1) was elevated by 700.26 %, indicating horizontal gene transfer of ARGs. Eventually, bioaugmentation was efficient in regulating microbial metabolism, relieving antibiotic stress, and eliminating antibiotics in composting. However, the ability to remove ARGs should be further investigated. Such an approach should be further considered for treating pollutants-influenced organic waste to eliminate environmental concerns.

Occurrence of antibiotic resistance genes carried by plastic waste from mangrove wetlands of the South China Sea

Plastic waste can carry organisms such as bacterial pathogens and antibiotic resistance genes (ARGs) over long distances. However, only few studies have been conducted on the occurrence of ARGs in plastic waste from mangrove wetlands. This study evaluated the distribution characteristics and ecological risks of plastic waste from mangroves in the coastal areas of the South China Sea. The correlation between anthropogenic activity levels and abundance of ARGs in mangroves was evaluated. Transparent and white were the common colors of plastic waste in mangroves. The main shapes of plastic waste were foam and film. The predominant types of plastic waste order were as follows: polyethylene (30.18 %) > polypropylene (27.51 %) > polystyrene (23.59 %). The living area (LA) mangroves had the highest polymer hazard and pollution load indices of 329.09 and 10.03, respectively. The abundance of ARGs (5.08 × 10⁸ copies/g) on the plastic surface in LA mangroves was significantly higher than that of the other mangrove areas. Furthermore, there was a significant correlation between ARGs and intI1 on the plastic surface in mangroves. Correlation analysis between the ARGs and intI1 showed that most of the ARGs were correlated with intI1 except for msbA. In LA mangroves, sociometric and environmental factors showed significant correlations with the absolute abundances of the four ARGs and intI1, indicating that anthropogenic activities may lead to changes in the amount of ARGs on plastic surfaces. Furthermore, the ARG storage of plastic waste from different mangroves was as follows: protected areas (3.12 × 10¹⁷ copies) > living areas (2.99 × 10¹⁷ copies) > aquaculture pond areas (2.88 × 10¹⁷ copies). The higher ARG storage of LA mangroves, with the smallest area, greatly increased its ecological risk. The results of this study can provide basic data for processes that influence the distribution of plastic waste and ARGs in mangroves.

The Preparation Processes and Influencing Factors of Biofuel Production from Kitchen Waste

Kitchen waste is an important component of domestic waste, and it is both harmful and rich in resources. Approximately 1.3 billion tons of kitchen waste are produced every year worldwide. Kitchen waste is high in moisture, is readily decayed, and has an unpleasant smell. Environmental pollution can be caused if this waste is treated improperly. Conventional treatments of kitchen waste (e.g., landfilling, incineration and pulverization discharge) cause environmental, economic, and social problems. Therefore, the development of a harmless and resource-based treatment technology is urgently needed. Profits can be generated from kitchen waste by converting it into biofuels. This review intends to highlight the latest technological progress in the preparation of gaseous fuels, such as biogas, biohythane and biohydrogen, and liquid fuels, such as biodiesel, bioethanol, biobutanol and bio-oil, from kitchen waste. Additionally, the pretreatment methods, preparation processes, influencing factors and improvement strategies of biofuel production from kitchen waste are summarized. Problems that are encountered in the preparation of biofuels from kitchen waste are discussed to provide a reference for its use in energy utilization. Optimizing the preparation process of biofuels, increasing the efficiency and service life of catalysts for reaction, reasonably treating and utilizing the by-products and reaction residues to eliminate secondary pollution, improving the yield of biofuels, and reducing the cost of biofuels, are the future directions in the biofuel conversion of kitchen waste.

Leaching risk of antibiotic resistance contamination from organic waste compost in rural areas

Composting is an important decentralized technology for treating multiple biodegradable organic wastes in rural areas. However, compared to industrial composting (i.e., time and temperature protocols), rural composting is less well-controlled, and the risk of antibiotic resistance genes (ARGs) in these composts needs to be determined. We performed a quantitative determination of ARGs and both prokaryotes and eukaryotes to investigate the liquid-solid leaching ratio and the relationship between ARGs and microbial communities in solid and water extracts of composts collected from rural areas. We observed a high level of sulfonamides resistance genes and tetracyclines resistance genes (10^-4-10^-2 copies/16S copies). Tet-C and tet-X show the strongest leaching potential in rural organic waste composts with complex hosts in solid and liquid phases. This study showed high ARG abundances in compost solid and water extracts, highlighting the leaching risk of compost ARGs when exposed to runoff or groundwater during open storage and field application.

Reducing nitrogen loss during kitchen waste composting using a bioaugmented mechanical process with low pH and enhanced ammonia assimilation

Exploring the regulation of nitrogen transformation in bioaugmented mechanical composting (BMC) process for rural kitchen waste (KW) is essential to avoid the "not-in-my-backyard" phenomenon caused by nitrogen loss. Herein, nitrogen transformation and loss in BMC versus conventional pile composting (CPC) of KW were compared. The results showed that the total nitrogen loss in the BMC was 6.87-39.32 % lower than that in the CPC. The main pathways to prevent nitrogen loss in the BMC were reducing NH₃ by avoiding a sharp increase in pH followed by transforming the preserved NH₄⁺-N into recalcitrant nitrogen reservoir via enhanced ammonia assimilation. The enriched thermophilic bacteria with mineralization capacities (e.g., Bacillus and Corynebacterium) during rapid dehydration and heating in the BMC accumulated organic acids and easy-to-use carbon sources, which could lead to lower pH and ammonia assimilation enhancement, respectively. This study provides new ideas for formulating low-cost nitrogen conservation strategies in decentralized KW composting.

Enrofloxacin-induced transfer of multiple-antibiotic resistance genes and emergence of novel resistant bacteria in red swamp crayfish guts and pond sediments

Antibiotic resistance genes (ARGs) can be transferred from environmental microbes to human pathogens, thus leading to bacterial infection treatment failures. The aquaculture polluted by over-used antibiotics is considered as a notorious reservoir of ARGs. However, the origin, diachronic changes, and mobility of ARGs under antibiotic exposure in aquaculture systems remain elusive. Our findings showed that enrofloxacin application also increased the relative abundance of various ARGs in addition to quinolone-resistance genes and induced ARG dissemination in crayfish gut and sediment bacteria. Further investigation indicated that the transposase-mediated recombination was the major driver of horizontal gene transfer (HGT) of ARGs under antibiotic stress. Notably, enrofloxacin application also induced the generation of some metagenome-assembled genomes (MAGs) carrying multiple ARGs, which were identified as novel species. Additionally, Enterobacteriaceae constituted a mobile ARG pool in aquaculture. Therefore, aquaculture provides potential wide environmental pathways for generation and spread of antibiotic resistance. Our findings of ARG temporal variations and dissemination pattern in aquaculture with artificial use of antibiotics are critical to the management of antibiotic resistance, which is of great ecosystem and health implications.

Biochar reduces colloidal phosphorus in soil aggregates: The role of microbial communities

Colloidal phosphorus (P_coll) in paddy soils can pose a serious threat to the water environment. Biochar amendment not only directly absorb P_coll to reduce the runoff loss, but also create hotspots for microbial communities which simultaneously affects soil P_coll. However, despite the crucial role of microorganisms, it remains elusive regarding how biochar and its feedstock types affect the relationships of soil microbial communities and P_coll in soil matrix (such as at soil aggregate level). To address the knowledge gap, we explored the (in)direct effects of biochar on the soil P_coll in physically separated fractions including micro- (53-250 μm) and macroaggregates (250-2000 μm). Results showed that straw and manure biochars decreased the soil P_coll content by 55.2-56.7% in microaggregates and 41.2-48.4% in macroaggregates after 120 days of incubation, compared to the respective control. The fungal communities showed a significantly correlation (0.34, p < 0.05) with P_coll content in the macroaggregates, whereas the bacterial communities were extremely significantly correlated (0.66, p < 0.001) with P_coll content in the microaggregates. Furthermore, the partial least squares path model analysis indicated that biochar amendments directly increased P_coll content (0.76 and 0.61) in micro- and macroaggregates, but the reduced P_coll content by biochar was mainly derived from indirect effects, such as changed soil biological characteristics carbon (C)/P (-0.69), microbial biomass C (-0.63), microbial biomass P (-0.68), keystone taxa Proteobacteria (-0.63), and Ascomycota (-0.59), particularly for the macroaggregates. This study highlights that to some extent, biochar addition can reduce soil P_coll content by affecting microbial communities (some keystone taxa), and soil biological characteristics at soil aggregate level.

Microbial cooperation promotes humification to reduce antibiotic resistance genes abundance in food waste composting

Antibiotic resistance genes (ARGs) fate in a full-scale Food waste (FW) facility was investigated. Results showed that with the changes in ARGs, microbial networks could be naturally divided into two clusters, named as the ARGs increasing group (AI group) and the ARGs decreasing group (AD group). The significant difference between two groups (i.e. stronger microbial competition in the AI group and stronger microbial cooperation in the AD group) implied that the variation in ARGs over time were caused by a switch between competition and cooperation. These results indicated that microbial competition might increase ARGs abundance, while cooperation might reduce it. Meanwhile, structural-equation-model (SEM model) showed that humification indexes (e.g. GI value) was an indicator for characterizing microbial interactions and ARGs. The results of the linear model further confirmed that mature compost (GI values > 92.6 %) could reduce the risk of ARGs.

Sulfadiazine inhibits hydrogen production during sludge anaerobic fermentation by affecting pyruvate decarboxylation

The overuse and random discharge of antibiotics can cause serious environmental pollution. Sludge acts as a repository for antibiotics, its anaerobic fermentation process will inevitably be affected. This study investigated the effects of a typical antibiotic contaminant, sulfadiazine (SDZ), on the anaerobic fermentation of sludge for hydrogen production. Results demonstrated that the production of hydrogen was significantly inhibited by SDZ, and the inhibition was enhanced with increasing SDZ content. Within 5 days, the cumulative amount of hydrogen with 500 mg SDZ/kg dry sludge was 8.5 mL, which was only 32.2% of that in the control (26.4 mL). Mechanistic investigation showed that the reduced hydrogen production when SDZ existed was mainly attributed to the suppression of pyruvate decarboxylation during the hydrogen production stage, and the diversity of microorganisms, especially the abundance of microorganisms and the activities of key enzymes closely related to hydrogen production were inhibited with SDZ, resulting in less hydrogen accumulation.