Performance and mechanism of co-culture of Monascus purpureus, Lacticaseibacillus casei, and Saccharomyces cerevisiae to enhance lovastatin production and lipid-lowering effects.

To facilitate lipid-lowering effects, a lovastatin-producing microbial co-culture system (LPMCS) was constituted with a novel strain Monascus purpureus R5 in combination with Lacticaseibacillus casei S5 and Saccharomyces cerevisiae J7, which increased lovastatin production by 54.21% compared with the single strain R5. Response Surface Methodology (RSM) optimization indicated lovastatin yield peaked at 7.43 mg/g with a fermentation time of 13.88 d, water content of 50.5%, and inoculum ratio of 10.27%. Meanwhile, lovastatin in LPMCS co-fermentation extracts (LFE) was qualitatively and quantitatively analyzed by Thin-Layer Chromatography (TLC) and High-Performance Liquid Chromatography (HPLC). Cellular experiments demonstrated that LFE exhibited no obvious cytotoxicity to L-02 cells and exhibited excellent biosafety. Most notably, high-dose LFE (100 mg/L) exhibited the highest reduction of lipid accumulation, total cholesterol, and triglycerides simultaneously in oleic acid-induced L-02 cells, which decreased by 71.59%, 38.64%, and 58.85% than untreated cells, respectively. Overall, LPMCS provides a potential approach to upgrade the lipid-lowering activity of Monascus-fermented products with higher health-beneficial effects.

Synergistic biocontrol of Bacillus subtilis and Pseudomonas fluorescens against early blight disease in tomato.

Early blight of tomato caused by Alternaria solani results in significant crop losses. In this study, Bacillus subtilis J3 and Pseudomonas fluorescens J8 were co-cultured as a synthetic microbial community (BCA) for synergistic biocontrol of A. solani, and the inhibition mechanism was investigated. BCA presented an inhibition ration against A. solani at 94.91%, which lowered the disease incidence by 38.26-42.87%; reduced peroxidase, catalase, superoxide dismutase activity of tomatoes by 73.11-90.22%; and promoted the biomass by 66.91-489.21%. With BCA protection, the relative expression of tomato resistance genes (including gPAL2, SWRKY, PR-10, and CHI) in roots and leaves was 12.83-90.70% lower than without protection. BCA also significantly altered the rhizosphere and phyllosphere microbial community. The abundance of potentially beneficial bacteria, including Bacillus, Pseudomonas, Arthrobacter, Lysobacter, and Rhizobium, elevated by 6.58-192.77%. They were negatively correlated with resistance gene expression, indicating their vital involvement in disease control. These results provided essential information on the synergistic biocontrol mechanism of bacteria against pathogens, which could contribute to developing novel biocontrol strategies. KEY POINTS: • Bacillus and Pseudomonas present a synergistic biocontrol effect against A. solani. • Biocontrol prevents pathogen damage and improves tomato growth and systemic resistance. • Beneficial bacteria thrive in the rhizosphere is the key to microbial regulation.

Development and properties evaluation of multi-strain probiotic with cholesterol-lowering potential in vitro.

Probiotics have a cholesterol-lowering effect. Multi-strain probiotics (MSPs) outperformed single-strain probiotics due to the interaction of strains. Hence, we expect to develop a high-efficiency MSP for lowering cholesterol. Three strains, including Lactobacillus caseiS1, Enterococcus faeciumS4, and L. harbinensisS6, were used to develop the MSPs. To evaluate their effect, gastrointestinal tolerance, bile salt hydrolase (BSH) activity, cholesterol-lowering rate, antioxidant ability, gamma-aminobutyric acid (GABA) production, and antibiotic sensitivity were determined. The triple lactic acid bacteria probiotic (TLP) was the most efficient one. After 24 h treatment with artificial gastric fluid, 47.88% of TLP survived. TLP exhibited the highest BSH activity (149.40 U·ml-1) and cholesterol-lowering rate (75.05%) in vitro, with co-precipitation reducing the majority of cholesterol. The reducing power and superoxide radical scavenging rate of the cell-free supernatant and the hydroxyl radical scavenging rate in viable cells were 1.52, 85.03%, and 89.66%, respectively, and the GABA production was 0.67 mg·ml-1, which enhanced the health benefit effects. By fuzzy mathematical analysis, TLP was the optimal probiotic and was competitive with commercial probiotics. The three strains were susceptible to 13 antibiotics. Therefore, TLP has the potential to develop into a cholesterol-lowering probiotic preparation.

Effect and mechanism of simultaneous cadmium-tetracycline removal by a self-assembled microbial-photocatalytic coupling system.

Electrochemical bacteria Shewanella oneidensis MR-4 (MR-4) was used to biologically generate cadmium sulfide (bio-CdS) nanocrystals and construct a self-assembled intimately coupled photocatalysis-biodegradation system (SA-ICPB) to remove cadmium (Cd) and tetracycline hydrochloride (TCH) from wastewater. The characterization using EDS, TEM, XRD, XPS, and UV-vis confirmed the successful CdS bio-synthesis and its visible-light response capacity (520 nm). 98.4% of Cd2+ (2 mM) was removed during bio-CdS generation within 30 min. The electrochemical analysis confirmed the photoelectric response capability of the bio-CdS as well as its photocatalytic efficiency. Under visible light, SA-ICPB entirely eliminated TCH (30 mg/L). In 2 h, 87.2% and 43.0% of TCH were removed separately with and without oxygen. 55.7% more chemical oxygen demand (COD) was removed with oxygen participation, indicating the degradation intermediates elimination by SA-ICPB required oxygen participation. Biodegradation dominated the process under aerobic circumstances. Electron paramagnetic resonance analysis indicated that h+ and ·O2- played a decisive role in photocatalytic degradation. Mass spectrometry analysis proved that TCH was dehydrated, dealkylated, and ring-opened before mineralizing. In conclusion, MR-4 can spontaneously generate SA-ICPB and rapidly-deeply eliminate antibiotics by coupling photocatalytic and microbial degradation. Such an approach was efficient for the deep degradation of persistent organic pollutants with antimicrobial properties.

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.

Strategy for enhancing Cr(VI)-contaminated soil remediation and safe utilization by microbial-humic acid-vermiculite-alginate immobilized biocomposite.

Bioreduction is an efficient approach to in-situ remediate Cr(VI)-contaminated soil, but further strengthening methods are still urgently needed. Herein, a novel immobilized biocomposite (B-HA-VE-SA) was successfully synthesized by embedding a efficient strain Bacillus sp. CRB-7 with humic acid (HA) combined vermiculite (VE) and sodium alginate (SA). The performance and enhancement mechanism of the immobilized biocomposite on remediating Cr(VI)-contaminated soil were also investigated by analyzing the whole-genome of CRB-7, Cr(VI) detoxification, soil microecological regulation, and subsequent crop growth response. Genomic annotation demonstrated that CRB-7 contains multiple genes contributed to Cr(VI) tolerance, Cr(VI) reduction and other metals resistance. Results showed that embedded CRB-7 biocomposites exhibited more effective reduction of Cr(VI) in soil compared with control and free CRB-7 treatment, especially B-HA-VE-SA achieved the highest Cr(VI) removal efficiency (96.18%) and the residual Cr proportion (49.04%) via multiple mechanisms including carrier effects, nutrient sustained-release, and electron-shuttle effect enhanced the bioremediation process. Furthermore, the synergies of CRB-7 and immobilizers (HA, VE and SA) significantly improved soil microecology (soil enzyme activities, microbial quantity and diversity), and engendered the evolution of microbial community composition and functional pathways. Consequently, pot experiments (Brassica napus L.) verified the plant-growth-promoting (12.00-18.00% and 43.82-69.00% higher in emergence rate and biomass) and Cr-accumulation-reducing effects (19.47-91.09% and 29.11-89.80% lower in root and aerial parts) of free and immobilized CRB-7. Taken together, these findings highlighted the superiority of B-HA-VE-SA in simultaneous remediation, microecological improvement and safe utilization of Cr(VI)-contaminated soil.

Responsive change of crop-specific soil bacterial community to cadmium in farmlands surrounding mine area of Southeast China.

In arable soils co-influenced by mining and farming, soil bacteria significantly affect metal (Cadmium, Cd) bioavailability and accumulation. To reveal the soil microecology response under this co-influence, three intersection areas (cornfield, vegetable field, and paddy field) were investigated. With a similar nutrient condition, the soils showed varied Cd levels (0.31-7.70 mg/kg), which was negatively related to the distance from mining water flow. Different soils showed varied microbial community structures, which were dominated by Chloroflexi (19.64-24.82%), Actinobacteria (15.49-31.96%), Acidobacteriota (9.46-20.31%), and Proteobacteria (11.88-14.57%) phyla. A strong correlation was observed between functional microbial taxon (e. g. Acidobacteriota), soil physicochemical properties, and Cd contents. The relative abundance of tolerant bacteria including Vicinamibacteraceae, Knoellia, Ardenticatenales, Lysobacter, etc. elevated with the increase of Cd, which contributed to the enrichment of heavy metal resistance genes (HRGs) and integration genes (intlI), thus enhancing the resistance to heavy metal pollution. Cd content rather than crop species was identified as the dominant factor that influenced the bacterial community. Nevertheless, the peculiar agrotype of the paddy field contributed to its higher HRGs and intlI abundance. These results provided fundamental information about the crop-specific physiochemical-bacterial interaction, which was helpful to evaluate agricultural environmental risk around the intersection of farmland and pollution sources.

Dispersion, olfactory effect, and health risks of VOCs and odors in a rural domestic waste transfer station.

The impact of odorous gases emitted from refuse transfer stations has always been a concern raised by the surrounding residents. The emitted volatile organic compounds (VOCs) and odors were investigated in a rural solid waste transfer station (RSWTS) located in Southwest China. A total of 70 VOCs were identified and quantified. The total VOCs (TVOCs) concentrations varied from 848.38 to 31193.24 µg/m3. Inorganic odor and greenhouse gases concentrations ranged from 39.11 to 470.14 µg/m3 and 1.03-525.42 µg/m3, respectively. Oxygenated compounds contributed the most (58.25%) to the VOCs. Among the oxygenated compounds, ketones, esters, and ethers were the dominant categories, accounting for 67.5%, 12.70%, and 11.85%, respectively. The key odorants included propionaldehyde, hexanaldehyde, propionic acid, acetaldehyde, and disopropyl ether. N-nitrosodiethylamine, acrylonitrile, and 1,3-Butadiene were the three main carcinogens that pose considerable risk to human health. Allyl chloride was the most non-carcinogenic pathogen among the VOCs detected in RSWTS. With diffusion in the downwind direction, the concentration of VOCs decreased gradually, and their risks weakened accordingly. At the sampling site of RSWTS-10, located 100 m away from RSWTS, acrylonitrile and 1,3-Butadiene still presented an unacceptable carcinogenic risk to human health. This study provides new data for assessing the emission characteristics, olfactory effects, and health risks of trace VOCs, especially those released from RSWTS.

Lipid degrading microbe consortium driving micro-ecological evolvement of activated sludge for cooking wastewater treatment.

In this study, a lipid degrading microbe consortium (LDMC) was assembled to improve the performance of activated sludge (AS) on cooking wastewater purification. LDMC can rapidly degrade high-level oil (efficiency beyond 93.0% at 5.0 g/L) as sole carbon source under various environmental conditions (10.0-45.0 °C, pH 2.0-12.0). With LDMC inoculation, AS' water treatment performance was significantly enhanced, which removed 36.10 and 48.93% more chemical oxygen demand (COD) and ammonia nitrogen from wastewater than control. A better settling property and smaller bulking risk were found with LDMC inoculation, indicated by a lower SV30 and SVI index but a higher MLSS. By GC/MS analysis, a gradual degradation on the end of the fatty acid chain was suggested. LDMC inoculation significantly changed AS's microbial community structure, improved its stability, decreased the microbial community diversity, facilitated the enrichment of lipid degraders and functional genes related to lipid bio-degradation. Lipid degraders including Nakamurella sp. and Stenotrophomona sp., etc. played a crucial role during oil degradation. Sludge structure maintainers such as Kineosphaera sp. contributed largely to the stability of AS under exogenous stress. This study provided an efficient approach for cooking wastewater treatment along with the underlying mechanism exploration, which should give insights into oil-containing environmental remediation.

Trace volatile compounds in the air of domestic waste landfill site: Identification, olfactory effect and cancer risk.

Landfill sites are regarded as sources of volatile compounds (VOCs) and odors emitted to the atmosphere. Surface emissions of VOCs and odors were investigated in a rural domestic waste landfill site located in southwest China. A total of 76 chemical compounds belonging to 3 chemical families were identified and quantified. The total number of VOCs (TVOC) detected ranged from 18.1 to 806.3 mg/m3, while odorous gases and greenhouse gases ranged from 0.4 to 21.2 and 0-100.5 mg/m3, respectively. High emissions were found in the air surrounding the leachate storage pool (LSP) and dumping area (DPA). The dominant species of VOCs were hexaldehyde, m-xylene, propylene oxide, acetophenone, and 2-butanone. The traceability analysis showed that the odors and VOCs diffused to the downwind boundary mainly came from the DPA and LSP. According to the olfactory effect analysis and cancer risk assessment, the main odor-causing gaseous pollutants were hydrogen sulfide, propionic acid, styrene, and 2-pentanone, while benzene, trichlorethylene, and 1,3-butadiene were the dominant carcinogens. This study provides new insights into the emission characteristics, olfactory effects, and cancer risks of VOCs and odors emitted from rural domestic solid waste landfill sites.

Coupled with EDDS and approaching anode technique enhanced electrokinetic remediation removal heavy metal from sludge.

In this work, the novel technology was used to remove heavy metal from sludge. The coupled with biodegradable ethylenediamine disuccinic acid (EDDS) and approaching anode electrokinetic (AA-EK) technique was used to enhance heavy metal removing from sludge. Electric current, sludge and electrolyte characteristics, heavy metal removal efficiency and residual content distribution, and heavy metal fractions percentage of variation were evaluated during the electrokinetic remediation process. Results demonstrated that the coupled with EDDS and AA-EK technique obtain a predominant heavy metal removal efficiency, and promote electric current increasing during the enhanced electrokinetic remediation process. The catholyte electrical conductivity was higher than the anolyte, and electrical conductivity of near the cathode sludge achieved a higher value than anode sludge during the coupled with EDDS and AA-EK remediation process. AA-EK technique can produce a great number of H+, which caused the sludge acidification and pH decrease. Cu, Zn, Cr, Pb, Ni and Mn obtain the highest extraction efficiency after the coupled with EDDS and AA-EK remediation, which were 52.2 ± 2.57%, 56.8 ± 3.62%, 60.4 ± 3.62%, 47.2 ± 2.35%, 53.0 ± 3.48%, 54.2 ± 3.43%, respectively. Also, heavy metal fractions analysis demonstrated that the oxidizable fraction percentage decreased slowly after the coupled with EDDS and AA-EK remediation.

Influence of moisture content on chicken manure stabilization during microbial agent-enhanced composting.

Moisture content (MC) influences substance transformation during composting and the function of exogenous microbial agents. Unsuitable MC could cause leaching, nutrient loss, and secondary contamination. In this study, chicken manure composting with varied MC (45-61%) was conducted under functional microbial agent inoculation to explore the optimum condition for composting and the potential mechanism. Due to the enhanced decomposing, nitrosation, and nitrification effect lead by the functional microorganism, treatment with the optimal MC (53%) exhibited the highest composting temperature (61 °C) and longest high-temperature period (15 days), achieving a final carbon-nitrogen ratio (C/N), humic acids and fulvic acids ratio (HA/FA), and NH4+-N/NO3--N at 19.20, 2.00, and 0.93, respectively. After composting, the total nitrogen (TN) increased by 13.01-22.10% in the treatments with microbial agent inoculation compared with original stack, while it decreased by 7.76% in control. The highest nutrient (5.63%, 5.63-14.20% higher than the other composts) and better product safety (11.43-23.58% higher seed germination than others) were observed in treatment with MC at 53%, exceeding the Chinese national standard for organic fertilizer. Obviously, under optimum MC, microbial agent augmentation lead to high quality and safe compost products after a short composting period (25 days) without any leaching, which suggested an efficient way to promote the recycling and recovery of husbandry waste.

Microbial response during treatment of different types of landfill leachate in a semi-aerobic aged refuse biofilter.

In this research, for the first time, three kinds of landfill leachate (young (YL), mature (ML) and mixed (MYL) leachate) were treated in a semi-aerobic aged refuse biofilter (SAARB) to compare the effectiveness of, and microbial changes in, this biofilter when treating leachates that have significantly different characteristics. The SAARB achieved stable removal of organic matter from all three leachates and reduced the concentrations of aromatic substances. The best treatment was achieved with YL, followed in order by MYL and ML. The removal of nitrogen from all three leachates by the SAARB was particularly significant. The microbial abundance and diversity in the media of the SAARB changed after treatment of the three leachates, and the order of change from small to large was ML# < MYL# < YL#. The microbial communities were mainly affected by (and negatively correlated to) the relative content of refractory organics in leachate. Proteobacteria was the dominant microorganism. Deinococcus-thermus responded most to the quality of leachate being treated, increasing in relative abundance as the content of refractory organics increased. This was opposite to the response of Chloroflexi. In YL# the dominant species at the genus level was Thauera, and in ML# the dominant species were Truepera and Iodidimonas. The microbial activity and metabolic intensity were enhanced after treatment of the different leachates. The expression of nitrification-related genes was the strongest and the total abundance was the highest when YL was treated. This study promotes the optimization and application of SAARB.

Hydroxyl radical-based and sulfate radical-based photocatalytic advanced oxidation processes for treatment of refractory organic matter in semi-aerobic aged refuse biofilter effluent arising from treating landfill leachate.

In this study, three photolytic advanced oxidation processes (AOPs) were applied to the treatment of refractory organic matter in semi-aerobic aged refuse biofilter (SAARB) effluent, and the treatment efficiencies of the three AOPs were systematically compared. The AOPs combined ultraviolet (UV) radiation with either hydrogen peroxide (UV-H2O2), peroxymonosulfate (UV-PMS) or both oxidants (UV-PMS/H2O2). The effects of key parameters on degradation characteristics of refractory organics, and the contribution of reactive oxygen species were systematically studied. Results indicated that UV radiation can greatly enhance treatment efficiencies of both PMS and H2O2. Furthermore, decreasing n(H2O2)/n(PMS) ratio and decreasing the reaction pH can increase treatment efficiency for refractory organics. Compared on the basis of chemical oxygen demand (COD), treatment efficiency followed the order UV-PMS (COD removal 37.39%) > UV-PMS/H2O2 (30.51%) > UV-H2O2 (28.59%) which is consistent with results from ultraviolet-visible spectra analysis. HO• and SO4•- were both identified in the UV-PMS/H2O2 and UV-PMS processes. In the UV-PMS process, SO4•- was the dominant ROS, which suggested that SO4•--based AOPs are better than HO•-based AOPs for degrading refractory organics contained in SAARB effluent. Parallel factor (PARAFAC) analysis indicated that UV-based AOPs were effective in degrading humic- and fulvic-like substances in the SAARB leachate, and the UV-PMS process achieved a much better degradation efficiency of refractory organics in the leachate than did the UV-PMS/H2O2 and the UV-H2O2 processes. Furthermore, the best treatment efficiency was achieved by the UV-PMS process and this process also consumed the least electrical energy. This study provides a theoretical reference for refractory organics degradation in SAARB effluent by UV-catalyzed AOPs.

Effect of waste compaction density on stabilization of aerobic bioreactor landfills.

Landfill stabilization contributes to the safe operation and maintenance of landfills. This study used a simulated aerobic bioreactor landfill to investigate the impact of different compaction densities on its stabilization to provide a basis for optimal parameter selection during landfill design. Samples of municipal solid waste were tested with compaction densities of 450, 500, 550, 600, and 650 kg/m3 during the experiment. The optimum compaction density was obtained by periodically monitoring the temperature of the waste pile, the water quality of leachate, and the composition of the waste. The impacts of waste compaction density on waste pile temperature and leachate were investigated and coupled with the analysis of waste composition to discuss the possible reaction mechanism. Results showed that the most complete waste degradation occurred at 550 kg/m3 compaction density, which was effective at accelerating stabilization of the simulated aerobic bioreactor landfill. Limitations of the experiment are given to lay foundations for further study.

Characteristics and exposure risks of potential pathogens and toxic metal(loid)s in aerosols from wastewater treatment plants.

Aerosols from wastewater treatment plants (WWTPs) are considered to be potentially hazardous to on-site employees and surrounding residents. However, their harmful components and their effects remain poorly understood. In this study, the characteristics, responsible factors, sources and exposure risks of potential pathogens and toxic metal(loid)s in aerosols from four WWTPs were investigated. There were 21 potential pathogens and 15 toxic metal(loid)s detected in the aerosols. Arcobacter and Fe were the dominant taxa responsible for the dissimilarity of the potential pathogen population and toxic metal(loid) composition between the aerosols and the wastewater/sludge, respectively. Both meteorological factors and sources affected pathogen and toxic metal(loid) composition. The potential pathogens and toxic metal(loid)s in indoor aerosols mainly originated from wastewater/sludge, while those in outdoor aerosols originated from wastewater/sludge and ambient air. The highest respirable fraction (<3.30 µm) concentrations and proportions were detected at the aeration units. Non-carcinogenic and carcinogenic risks of toxic metal(loid)s for both adults and children were found within and/or around WWTPs, and non-carcinogenic risks of bacteria for children were found at downwind, suggesting the need for active safeguard procedures, such as that employees wear masks and work clothes, covering the main emission sites, and collecting and destroying of aerosols.

Screening pesticide residues on fruit peels using portable Raman spectrometer combined with adhesive tape sampling.

In this work, we report a simple and rapid surface-enhanced Raman scattering (SERS) method for the screening of pesticide residues on fruit peels using a portable Raman spectrometer. Adhesive tapes were used as the sampling media; the effectiveness of different tape brands was examined. Collection efficiencies were found to be 60.2 ±â€¯7.6%, 54.3 ±â€¯5.0%, and 52.3 ±â€¯9.0% on glass, aluminum foil, and fruit peels, respectively. SERS was achieved by applying silver nanoparticles (Ag NPs) to the surface of the tape after analyte collection. Preparation of the Ag NPs was optimized for pesticide detection. The limit of detection of triazophos on apple peels was 25 ng/cm2 with the portable Raman spectrometer. Considering the least favorable conditions, the calculated detection limit was 0.0225 mg/kg, which is an order of magnitude less than the maximum residue limit (MRL, 0.2 mg/kg) in China. The method is sufficiently sensitive for use in field analysis.

Succession and diversity of microbial communities in landfills with depths and ages and its association with dissolved organic matter and heavy metals.

Landfill is an important method for the treatment of municipal solid wastes. Microbes play a central role in the biodegradation and stabilization of organic matter during landfill; however, the succession of microbial communities in landfills and their association with organic matter still remain unclear. This study investigated the succession and diversity of microorganisms in landfill depending on different depths and ages as well as its association with dissolved organic matter (DOM) and heavy metals. The results showed that the actinobacterial diversity and richness were high compared to bacteria in young landfill cells. The diversity and richness of bacteria and actinobacterial were the highest in the middle layer in the intermediate and old landfill cells. Firmicutes, Proteobacteria, and Actinobacteria were the most dominant phyla. Firmicutes were mainly affected by the humification degree, and the aromatic and protein-like substance content of the landfill-derived DOM. The phylum Proteobacteria was greatly affected by the lipid and humic-like substances content of the landfill-derived DOM, while the distribution of Actinobacteria was regulated by both aromatic and humic-like substances. The effect of dissolved heavy metals on the microbial distribution in landfill differed for the metals Cr, Ni, Pb, Mn, Cu, Zn, and Cd. Siderophile elements (Cr, Ni, and Pb) were necessary trace elements for Proteobacteria and Actinobacteria, and promoted their growth. Oxyphilic element (Mn) was an important factor promoting the growth of Actinobacteria. However, no apparent relationship was found between sulfurophile elements (Cu, Zn, and Cd) and microorganisms.

Light and Magnetic Dual-Responsive Pickering Emulsion Micro-Reactors.

Emulsion droplets can serve as ideal compartments for reactions. In fact, in many cases, the chemical reactions are supposed to be triggered at a desired position and time without change of the system environment. Here, we present a type of light and magnetic dual-responsive Pickering emulsion microreactor by coadsorption of light-sensitive titania (TiO2) and super paramagnetic iron oxide (Fe3O4) nanoparticles at the oil-water interface of emulsion droplets. The droplets encapsulating different reactants in advance can be driven close to each other by an external magnetic field, and then the chemical reaction is triggered by UV illumination due to the contact of the isolated reactants as a result of droplet coalescence. An insight into the incorporation of hydrophobic TiO2 and hydrophilic Fe3O4 nanoparticles simultaneously at the emulsion interface is achieved. On the basis of that, an account is given of the coalescence mechanism of the Pickering emulsion microreactors. Our work not only provides a novel Pickering emulsion microreactor platform for triggering chemical reactions in a nonintrusive and well-controlled way but also opens a promising avenue to construct multifunctional Pickering emulsions by assembly of versatile building block nanoparticles at the interface of emulsion droplets.