The microbiological water quality of drinking water distribution systems (DWDSs) is of primary importance for public health. The detachment of biofilm attached on the pipe wall attribution to water ...source switch and the occurrence of potentially pathogenic chlorine-resistant bacteria (CRB) under chlorine disinfection get lots of attention. Studies examining microbial communities after the water source switch, particularly in low-salinity water, have been scant. The UV‑chlorine combined disinfection applied in one of the investigated drinking water plants provided insight into the control of CRBs. We applied high-throughput sequencing of the 16S rRNA gene to characterize the bacterial communities of the DWDS in northern China over 1 year. A network comprising four different DWDSs was sampled at 48 sites every season (temperate continental monsoon climate), and the impact of key spatial-temporal and physicochemical parameters was investigated. Overall, the entire bacterial community was not significantly different among the four DWDSs (spatial parameter) but varied with seasons (temporal parameter). The switch in water sources might increase the relative abundance of potentially opportunistic pathogens in DWDSs. UV‑chlorine combined disinfection can decrease community diversity and is likely to control the growth of potential opportunistic pathogens in DWDSs.
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•The spatial-temporal of bacterial community in DWDSs was investigated.•UV/chlorine disinfection effectively controlled potential opportunistic pathogens.•High risk caused by trans-regional water diversion switch to local water.
This article presents investigation of the flavor profile on 5 different regional Chinese smoked chicken samples using gas chromatography−ion mobility spectrometry analysis methods. Five batches of ...samples were obtained over the course of 6 mo. A total of 34 flavor substances were identified in the 5 smoked chicken samples, including 10 aldehydes, 7 alcohols, 4 ketones, 2 hydrocarbons, 3 heterocyclic compounds, 4 esters, 2 ethers, and 2 phenolic compounds. The whole spectral fingerprint visually displayed flavor differences and relations in 5 types of smoked chicken with local characteristics. Moreover, the orthogonal projections to latent structures discriminant analysis model revealed that these samples could be separately classified into 5 groups. Multivariate statistical analysis showed that 20 chemicals with higher Variable Importance for the Projection values were the key contributors to the differences of flavor in these 5 kinds of smoked chicken. N-nonanal, heptanal, n-nonanal, heptanal, furfurol, and hexanal were the main common flavor compounds in the 5 types of Chinese smoked chicken, whereas linalool, alpha-terpineol, 1,8-cineole, and anethole were the main characteristic flavor compounds of Goubangzi chicken (No. 1); gamma-butyrolactone, 2-acetylfuran, 2-methoxyphenol, 2-acetylpyrrole, and limonene were determined as the key flavor compounds of Liaocheng chicken (No. 2); the concentration of octanal and n-nonanal was higher in Tangqiao chicken (No. 3); butyl acetate was the key contributor to the flavor compounds of Jinshan chicken (No. 4). 2-Heptanone and 2-pentylfuran had a high correlation with Zhuozishan chicken (No. 5). The different raw materials and ingredients used, especially the method of preparation and cultural differences, in different regions of the country in China were the main reasons leading to the similarities and differences of volatile compounds in the 5 kinds of Chinese traditional smoked chicken.
Abstract
In order to control the rotation of the end effector in a long and narrow space, a spatial parallel mechanism that can realize 2 degrees of freedom rotation is proposed. In this article, the ...forward kinematics model is established according to the constraint conditions of the mechanism’s pose, and the closed vector method is used to obtain the inverse kinematics model. Then based on the kinematics results, the dynamic inverse solution model was established by Newton-Euler method, and the dynamic analysis of the whole mechanism was carried out. Finally, the theoretical calculation results are compared with the simulation results of Adams software to verify the accuracy of the solution process.
Modified graphene/muscovite (MGMu) nanocomposite was synthesized with muscovite (Mu) and silane coupling agent modified graphene oxide through a simple hydrothermal method that exhibited excellent ...dispersion stability in oil. Compared with the base oil sample, the average friction coefficient and wear scar diameter of the MGMu oil sample decreased by 64.4 and 20.0%, respectively, and the microhardness of its wear scar was increased by 16.1%. The MGMu showed better tribological performance than its individual component due to the synergetic effect between the two components. The lubrication mechanism was proposed according to the morphology, chemical composition, and microhardness of the surface of wear scars. MGMu as an oil additive could fill between the friction pairs, cling to some asperities, and occur relative sliding between unit layers, thus playing a role in lubrication. It was found that MGMu would react with the surface of the friction pair during the friction process to generate Fe2O3, SiO2, SiC, and new aluminosilicate, which formed a self-repairing layer with high hardness. This chemically reactive film exhibited a lower shear strength, which made the oil sample containing MGMu have a lower coefficient of friction.
This study was intended to characterize six types of commercial smoked chicken products in China by using gas chromatography-mass spectrometry (GC-MS), odor-activity values (OAVs), and sensory ...evaluation. Results demonstrated that a total of 89 components were identified in all samples, and 34 were considered as odor-active compounds because their OAVs were greater than one. Liaocheng Chicken that smoked with fruit tree sawdust had more phenols, which contributed to the smoky aroma. Jinshan and Goubangzi Chicken that smoked with sugar had more furans which contributed the overall odor with sweety and caramel aroma. Zhuozishan and Laoting Chicken that smoked with sugar and wood chips had similar flavor and volatile compounds. Tengqiao Chicken that smoked with sugar, tea and rice had significant difference with other chicken in smoky, bittern and caramel aroma (P< .05). The diversity of these smoked chicken flavors was mainly due to the cooking culture differences.
Antibiotic resistance genes (ARGs) are an emerging issue for drinking water safety. However, the seasonal variation of ARGs in drinking water distribution systems (DWDS) is still unclear. This work ...revealed the tempo-spatial changes of microbial community, ARGs, mobile genetic elements (MGEs) co-occurring with ARGs, ARG hosts in DWDS bulk water by means of metagenome assembly. The microbial community and antibiotic resistome varied with sampling season and site. Temperature, ammonia, chlorite and total plate count (TPC) drove the variations of microbial community structure. Moreover, environmental parameters (total organic carbon (TOC), chlorite, TPC and hardness) shifted antibiotic resistome. ARGs and MGEs co-occurring with ARGs showed higher relative abundance in summer and autumn, which might be attributed to detached pipe biofilm. In particular, ARG-bacitracin and plasmid were the predominant ARG and MGE, respectively. ARG hosts changed with season and site and were more diverse in summer and autumn. In winter and spring, Limnohabitans and Mycobacterium were the major ARG hosts as well as the dominant genera in microbial community. In addition, in summer and autumn, high relative abundance of Achromobacter and Stenotrophomonas were the hosts harboring many kinds of ARGs and MGEs at site in a residential zone (0.4 km from the water treatment plant). Compared with MGEs, microbial community had a greater contribution to the variation of antibiotic resistome. This work gives new insights into the dynamics of ARGs in full-scale DWDS and the underlying factors.
•Impact of microbial structure on biological activated carbon filters investigated•Wood- and coal-based filters selected for distinct bacterial communities•Microbes in filters may be more cooperative ...than competitive•Micro-level macropores in filters impacted the abundance of keystone species
A new focus on biofiltration has emerged that aims to shape microbial communities to improve treatment efficacy. It is therefore necessary to understand the linkages between microbial community structure and biofilter function. However, the assembly and interaction of microbial communities in biological activated carbon (BAC) filters are unknown. In this study, we selected one coal-based granular activated carbon (GAC), GAC-13, with simultaneously developed micropore and micro-level macropore volume used for a bench-scale BAC column experiment, and compared it with other coal-based GACs and wood-based GAC in terms of the dissolved organic carbon (DOC) removal and microbial community characteristics. The results showed that there was no difference between the DOC removal efficiency of BAC-13 and the other two coal-based BAC filters with high iodine value in the period dominated by adsorption, while the DOC removal efficiency of BAC-13 (64.7±0.6%) was significantly higher than that of other BAC filters (36.3±0.8–54.1±0.4%) with a difference of 0.3–0.7 mg/L in DOC during the steady state. The bacterial communities were strongly assembled by deterministic rather than stochastic factors, where the surface polarity of GAC had a greater effect on the microbial communities than its physical properties. The corresponding co-occurrence network revealed that microbes in the BAC filter may be more cooperative than competitive. The keystone bacterium Hyphomicrobium, which had a relatively low abundance, contributed 0.3–1% more to the most abundant functions and produced 5–21 proteins/(g·GAC) more than the dominant bacterium Sphingobium. The metaproteomic-based approach could provide more accurate information regarding the contributions of different species to metabolic functions. The pore size distribution of GAC was found to be an important factor in determining BAC filter performance; the most important pore sizes were micropores and micro-level macropores (0.2–10 μm and >100 μm in diameter), and the latter impacted the abundance of keystone species. Overall, our findings provide new insights into shaping microbial communities by optimizing pore size structure to improve BAC performance, especially the abundance of keystone species.
Graphical Abstract
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•UV-LED 265 was the most efficacious at destroying CRB because it damaged their DNA.•Pseudomonas aeruginosa had the lowest resistance to all UV wavelengths & fluencies.•222-nm UV ...induced ROS & photosensitive substances that damage membranes.•265-nm UV induced DNA-pyrimidine dimers that inhibited transcription & translation.
The widespread use of chlorine disinfectants in drinking water has accelerated the selection of chlorine-resistant bacteria (CRB). The presence of CRB in drinking water (during treatment, distribution, and consumption) has a profound impact on public safety. Ultraviolet (UV) irradiation is an effective control technology for CRB. Nevertheless, the relative efficacies of different UV light wavelengths (traditional mercury lamps, ultraviolet light-emitting diodes (UV-LED 265 nm and 285 nm), and 222 nm krypton-chlorine excilamps) in the control and inactivation of various CRB have not been investigated. In this study, the impacts of different UV light sources on the inactivation rate and microbial cell structure of CRB were evaluated. The results showed that the order of inactivation efficacy was as follows: UV-LED 265 nm > low-pressure ultraviolet (LPUV) ≈ medium-pressure ultraviolet (MPUV) ≈ 222 nm > UV-LED 285 nm. CRB was inactivated via DNA damage and additional ATP decline under UV-LED 265 nm, UV-LED 285 nm and LPUV irradiation, of which UV-LED 265 nm was the most effective based on fluence and inactivation rate constants. The inactivation mechanisms revealed that the 222 nm wavelength was significantly different from other wavelengths; it stimulated the production of a large number of reactive oxygen species (ROS) which resulted in bacterial cell membrane damage, ATP direct decline, and a small number of DNA lesions. Multispectral MPUV induced both of the foregoing mechanisms but mainly damaged DNA. The present study provides empirical evidence for the reasonable application of UV disinfection technology in the treatment of water and wastewater and their conduits and delivery systems.
Both drinking water treatment processes and distribution can lead to antibiotic resistome variation, yet the variation of antibiotic resistome in the whole drinking water supply system (DWSS) ...combined with seasonality remains unknown. In this study, microbial community, antibiotic resistome, mobile genetic elements (MGEs) co-existing with antibiotic resistance genes (ARGs) and ARG hosts would be explored along a DWSS for four seasons with metagenome assembly. Multidrug and bacitracin ARGs were dominant ARGs in DWSS. Integrase, plasmids, recombinase and transposase were major MGEs co-existing with ARGs. Filtration and disinfection treatments could alter the ARG relative abundance, mainly via changing the abundance of ARG hosts (Limnohabitans and Polynucleobacter), which was influenced by water total organic carbon (TOC) content. When TOC was relatively high, filtration could proliferate ARGs via promoting antibiotic resistance bacteria (ARB) but chlorine dioxide could decrease ARGs via killing ARB. Filtration played an important role in controlling ARGs by reducing ARB when TOC was relatively low. The stimulation effect of disinfection on ARGs existed in more oligotrophic environment. Distribution could enrich ARGs in higher temperature by increasing MGEs co-occurring with ARGs and diversifying ARG hosts. MGEs co-occurring with ARGs became more abundant and diverse in disinfected water in warmer seasons. Microbial community was the most important factor determining the antibiotic resistome along a DWSS. These findings extend the knowledge about how and why water treatment processes and pipe distribution shape drinking water antibiotic resistome in different seasons.
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•Water treatment and transportation changed the microbiome and resistome, dependent on season.•Limnohabitans and Polynucleobacter could represent the TOC-dependent variation of ARGs in DWTP.•MGEs and diverse ARG hosts contributed to ARGs proliferation in DWDS in warmer seasons.•Microbial community was the key determinant of antibiotic resistome in DWTP and DWDS.•Metagenome assembly accurately quantified the abundance of MGEs co-existing with ARGs and ARG hosts.
The dose–response behavior of pathogens and inactivation mechanisms by UV-LEDs and excimer lamps remains unclear. This study used low-pressure (LP) UV lamps, UV-LEDs with different peak wavelengths, ...and a 222 nm krypton chlorine (KrCl) excimer lamp to inactivate six microorganisms and to investigate their UV sensitivities and electrical energy efficiencies. The 265 nm UV-LED had the highest inactivation rates (0.47–0.61 cm2/mJ) for all tested bacteria. The bacterial sensitivity strongly fitted the absorption curve of nucleic acids at wavelengths of 200–300 nm; however, indirect damage induced by reactive oxygen species (ROS) was the leading cause of bacterial inactivation under 222 nm UV irradiation. In addition, the guanine and cytosine (GC) content and cell wall constituents of bacteria affect inactivation efficiency. The inactivation rate constant of Phi6 (0.13 ± 0.002 cm2/mJ) at 222 nm due to lipid envelope damage was significantly higher than other UVC (0.006–0.035 cm2/mJ). To achieve 2log reduction, the LP UV lamp had the best electrical energy efficiency (required less energy, average 0.02 kWh/m3) followed by 222 nm KrCl excimer lamp (0.14 kWh/m3) and 285 nm UV-LED (0.49 kWh/m3).
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