Characterization of microbial consortia that reductively dechlorinate 4-chlorophenol and transform phenol to benzoate enriched from estuarine sediment of Lake Shinji

Monochlorophenols were degraded to benzoate via phenol by the initial dechlorination and the subsequent conversion of phenol to benzoate in anaerobic sediment samples of estuarine Lake Shinji under methanogenic conditions. To characterize bacteria that dechlorinate 4-chlorophenol and transform phenol to benzoate, we analyzed the microbial community structure of the enrichment culture with each 4-chlorophenol and phenol by the limiting dilution method with polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) of 16S rRNA gene. After serial dilution of the culture, the 4-chlorophenol-dechlorinating culture consisted of two dominant bacteria, one of which was most homologous with Dehalobacter sp. In the enriched culture with phenol, minor band homologous with Cryptanaerobacter phenolicass corresponded to the transformation activity.     

Complete mineralization of benzene by a methanogenic enrichment culture and effect of putative metabolites on the degradation

Microbial degradation of benzene under anaerobic conditions plays an important role in remediation of contaminated sites but the microorganisms and metabolic pathways involved remain poorly understood. In this study, we evaluated degradation of benzene by a methanogenic enrichment culture obtained from non-contaminated lotus field soil, alone and in the presence of several putative metabolic intermediates, that is, toluene, benzoate and phenol. Using stable isotope (¹³C) labeled substrate, benzene was shown to be degraded almost completely to equimolar concentrations of methane and carbon dioxide, without detectable accumulation of extracellular metabolites. Concurrently, toluene, benzoate and phenol were also effectively mineralized, but probably by microorganisms other than the benzene degraders. The latter included Hasda-A, which is putative benzene-degrading deltaproteobacterium present in the culture. While toluene and benzoate did not affect benzene degradation, phenol had a moderate inhibitory effect although it was not a major metabolic intermediate of benzene in our culture. Finally, 4-hydroxycoumarin was detected as a compound formed from phenol but further experiments are required to elucidate its relationship to degradation of phenol.     

苯酚及其衍生物对氨氮生物硝化的抑制研究

利用富集培养的硝化污泥研究了苯酚及其衍生物2,4-二氯苯酚、对氨基酚、邻甲基酚和对硝基酚对氨氮生物硝化过程的抑制特性。结果表明，上述5种酚类化合物对硝化细菌的抑制类型均为非竞争性抑制，抑制常数K_I和EC₅₀值相等，分别为2.61、1.92、8.50、1.18和6.65 mg/L。上述5种酚类化合物对硝化细菌的抑制程度由大到小的顺序为：邻甲基酚>2,4-二氯苯酚>苯酚>对硝基酚>对氨基酚。酚类化合物对硝化细菌的抑制是可逆的，通过简单的抑制剂稀释或洗涤可以使硝化细菌恢复活性。在保证出水水质的前提下，抑制剂存在时硝化工艺的泥龄被迫延长，且抑制程度越大，泥龄延长的程度越大。当系统受到有毒物质冲击时，和调控泥龄相比，调节工艺的进水流量或改变容积负荷是缓冲冲击的更简捷、快速和有效的途径。     

Adsorption of phenols by papermill sludges

In this paper we studied the sorption capacity of paper mill sludges for phenols. Phenol, 2-chlorophenol (2-CP), 3-chlorophenol 3-CP). 4-chlorophenol (4-CP), 2-nitrophenol (2-NP), 4-nitrophenol (4-NP), 2.4-dichlorophenol (2,4-DCP), 3,4-dichlorophenol (3,4-DCP) 3,5-dichlorophenol (3,5-DCP) and 2,4,5-trichlorophenol (2,4,5-TCP) were chosen for the sorption tests. Kinetic experiments showed that substituted-phenol sorption on papermill sludge was rapid (equilibrium was reached after 3 h); conversely, the time taken by the phenol to reach equilibrium conditions was 260 h. Experimental data showed that particle diffusion was involved in the sorption process but was not the only rate-limiting mechanism; several other mechanisms were involved. The adsorption isotherms showed the following order of retention capacity of papermill sludge: 2-NP = 4-NP < < 2-CP < phenol < 4-CP < or = 3-CP < 2,4 DCP<3,4 DCP=2,4,5 TCP<3,5 DCP. In all cases the experimental data showed a good fit with the Hill equation. which is mathemratically equivalent to the Langmuir-Freundlich model obtained by assuming that the surface is homogeneous, and that the adsorption is a cooperative process influenced by adsorbate-adsorbate interactions.     

Biodegradation of 2,4,6-trichlorophenol in the presence of primary substrate by immobilized pure culture bacteria

In this study, pure strains that are capable of utilizing 2,4,6-trichlorophenol have been isolated from the mixed culture grown on substrates containing chlorophenolic compounds. Studies have been carried out on the capability of these isolated pure strains in suspended and immobilized forms to decompose 2,4,6-trichlorophenol. Additionally, the influence of primary substrates (e.g., phenol, 2-chlorophenol, 3-chlorophenol, 4-chlorophenol, 2,4-dichlorophenol) on the decomposition of 2,4,6-trichlorophenol by the isolated pure strains grown in immobilized form is also investigated. The results are: Through bacterial isolation and identification, three pure strains have been obtained: Pseudomonas spp. strain 01, Pseudomonas spp. strain 02 and Agrobacterium spp. Whether in suspended or immobilized forms, all strains have poor removal efficiencies of 2,4,6-trichlorophenol. However, addition of 200 mg/l phenol will enable the immobilized Pseudomonas spp. strain 01, and Pseudomonas spp. strain 02 to achieve 65% and 48% removal of 2,4,6-trichlorophenol, respectively. Addition of phenol will assist the immobilized Pseudomonas spp. strain 02 in achieving removal of 2,4,6-trichlorophenol but the removal efficiency is not good if the phenol concentration is too low. The optimum phenol concentration should be between 200 and 400 mg/l.     

Benzoate degradation by Rhodococcus opacus 1CP after dormancy: Characterization of dioxygenases involved in the process

The process of benzoate degradation by strain Rhodococcus opacus 1CP after a five-year dormancy was investigated and its peculiarities were revealed. The strain was shown to be capable of growth on benzoate at a concentration of up to 10 g L^?1. The substrate specificity of benzoate dioxygenase (BDO) during the culture growth on a medium with a low (200–250 mg L^?1) and high (4 g L^?1) concentration of benzoate was assessed. BDO of R. opacus 1CP was shown to be an extremely narrow specificity enzyme. Out of 31 substituted benzoates, only with one, 3-chlorobenzoate, its activity was higher than 9% of that of benzoate. Two dioxygenases, catechol 1,2-dioxygenase (Cat 1,2-DO) and protocatechuate 3,4-dioxygenase (PCA 3,4-DO), were identified in a cell-free extract, purified and characterized. The substrate specificity of Cat 1,2-DO isolated from cells of strain 1CP after the dormancy was found to differ significantly from that of Cat 1,2-DO isolated earlier from cells of this strain grown on benzoate. By its substrate specificity, the described Cat 1,2-DO was close to the Cat 1,2-DO from strain 1CP grown on 4-methylbenzoate. Neither activity nor inhibition by protocatechuate was observed during the reaction of Cat 1,2-DO with catechol, and catechol had no inhibitory effect on the reaction of PCA 3,4-DO with protocatechuate.     

一株苯酚降解菌的筛选及降解动力学特性

利用富集驯化的培养方法,从首钢焦化厂废水处理系统中的二沉池出水中,分离筛选出一株能够高效降解苯酚的菌株B3对其16S rDNA序列进行分析,并选择Monod方程和Andrews方程分别研究该菌在不同苯酚浓度条件下的降酚动力学模式。结果表明,B3为蜡状芽孢杆菌(Bacillus cereus);苯酚浓度较低时,苯酚对菌株的生长基本不产生抑制作用,用Monod模型对B3降酚动力学过程进行拟合,其动力学参数V max=0.03 h-1,K s=25.53 mg/L;苯酚浓度较高时,按照Andrews模型对B3降酚动力学过程进行非线性最小二乘曲线拟合,其动力学参数V max=0.08 h-1,K s=147.52 mg/L,K i=384.96 mg/L。根据动力学方程,推论菌株B3降解对于浓度238.30 mg/L的苯酚具有最佳降解效果。     

A combined photolytic-electrolytic system for the simultaneous recovery of copper and degradation of phenol or 4-chlorophenol in mixed solutions

The effects of the presence of copper on the photooxidation of phenol and 4-chlorophenol and of the presence of the phenols on the recovery of copper by electrodeposition are studied in three systems: a photolytic cell in the presence and absence of TiO2 as a catalyst or H2O2 as an oxidant; an electrolytic cell and a combined photolytic-electrolytic system. The optimum system for the simultaneous removal of copper and destruction of the phenols which overcomes the effects of copper-phenol reactions is a combined system with concentrator electrode technology incorporated into the electrolytic cell. This combined system achieves >99% removal of copper and destruction of phenol or 4-chlorophenol in an 8 h period.     

Effect of operational factors on bioregeneration of binary phenol and 4-chlorophenol-loaded granular activated carbon using PVA-immobilized biomass cryogels

The effects of dry biomass density in cryogel beads, shaking speed and initial concentration ratio of phenol to 4-chlorophenol (4-CP) on the bioregeneration efficiencies of binary phenol and 4-CP-loaded granular activated carbon (GAC) for phenol and 4-CP, respectively, were investigated under the simultaneous adsorption and biodegradation approach. The results revealed higher bioregeneration efficiencies of binary-loaded GAC for phenol and 4-CP at higher dry biomass density but moderate shaking speed. The optimum dry biomass density in cryogel beads and shaking speed for use in bioregeneration were found to be 0.01 g/mL and 250 rpm, respectively. With respect to the initial phenol to 4-CP concentration ratio, the bioregeneration efficiencies were lower under increasing phenol and 4-CP initial concentrations, respectively, with the effect being more conspicuous under increasing 4-CP concentration. Higher bioregeneration efficiencies were achieved with the use of immobilized rather than suspended biomasses.     

Sodium bisulfate and a sodium bisulfate/tannin mixture decreases pH when added to an in vitro incubated poultry cecal or fecal contents while reducing Salmonella Typhimurium marker strain survival and altering the microbiome

The objective of the present study was to investigate the ability of animal feed-grade sodium bisulfate (SBS) and a mixture of sodium bisulfate/tannin to inhibit the growth of Salmonella using an anerobic in vitro mixed cecal culture to mimic the conditions within the chicken cecum. An initial inoculum of Salmonella Typhimurium was introduced to an anerobic dilution solution containing 1/3000 diluted cecal bacteria and solids consisting of ground chicken feed and different percentages of solid SBS or SBS/tannin, and surviving organisms were enumerated. Two different experimental designs were employed. In the “unadapted” treatment, the S. Typhimurium was added at the beginning of the culture incubation along with cecal bacteria and chicken feed/SBS or chicken feed/SBS/tannin. In the “adapted” treatment, S. Typhimurium was added after a 24 hour pre-incubation of the cecal bacteria with the chicken feed/SBS or chicken feed/SBS/tannin. Adding SBS resulted in reduction of pH in the cultures which paralleled with the reduction of S. Typhimurium. The SBS alone was found to be inhibitory to S. Typhimurium in the adapted treatment at all concentrations tested (0.25, 0.5, and 0.75%), and the degree of inhibition was concentration-dependent. Salmonella Typhimurium was completely killed in the adapted culture with 0.5% SBS after 24 and 48 h. The SBS/tannin mixture was less inhibitory than SBS alone at the same concentrations in side-by-side comparisons. Testing at a 0.5% SBS concentration, chicken age had little or no effect on log reduction of S. Typhimurium relative to age-matched control cultures without SBS, but age did affect the absolute number of S. Typhimurium surviving, with the greatest decreases occurring at 2 and 4 weeks of age (approx. 10³ S. Typhimurium surviving) compared to 6 weeks of age (approx. 10⁵ Salmonella surviving). Microbiome analysis with an Illumina MiSeq platform was conducted to investigate bacterial compositional changes related to the addition of SBS. The relative abundance of Firmicutes (at the phylum level) was decreased, and genera Lactobacillus and Faecalibacterium were increased when SBS was added to the anaerobic mixed culture containing either fecal or cecal material. The antimicrobial action of feed-grade SBS may represent a potential pre-harvest control measure for Salmonella in poultry production.     

Antimicrobial potential of commercial silver nanoparticles and the characterization of their physical properties toward probiotic bacteria isolated from fermented milk products

The application of nanotechnology in the agriculture and food sector is relatively recent compared to its usage in drug delivery or pharmaceuticals. Therefore, this paper presents a study of the effect of silver nanoparticles on probiotic bacteria based on the example of Lactobacillus acidophilus LA-5, Bifidobacterium animalis subsp. lactis BB-12 and Streptococcus thermophilus ST-Y31 isolated from fermented milk products. Probiotic bacteria are one of the most crucial groups of bacteria for the food industry, because of their claimed health-promoting properties. Studies have shown that the type and concentration of silver nanoparticle solutions have a significant impact on the tested probiotic bacteria which are profitable for the digestive system. In the presence of all tested silver nanoparticles, St. thermophilus ST-Y31 growth was inhibited significantly by the dilution method as opposed to the disk-diffusion method. Both the disk-diffusion and the dilution methods showed no significant differences between L. acidophilus LA-5 and B. animalis subsp. lactis BB-12. The concentrations 2 μg mL^?1 and 0.25 μg mL^?1 had the highest antibacterial activity and statistically significant impacts on the tested probiotic strains. To our knowledge, this is the first report on potential antimicrobial effect of nanosilver against the health-promoting probiotic bacteria L. acidophilus LA-5, B. animalis subsp. lactis BB-12 and St. thermophilus ST-Y31 isolated from fermented milk products.     

活性炭纤维上4-氯酚及焦化废水尾水的O3催化氧化降解实验研究

选择YT-1000型活性炭纤维（ACF）作为催化剂，考察ACF与O₃协同作用催化降解水溶液中4-氯酚的最佳反应条件，并将该条件应用于焦化废水生物处理尾水中难降解有机污染物的催化氧化。ACF表面具有丰富的微孔结构，对4-氯酚有良好的吸附作用，在动力学上提高了其与O3反应的起始浓度，并且在ACF表面含氧、含氮等基团的催化作用下发生氧化反应，1 L浓度为100 mg/L的4-氯酚水样中投加2 g ACF反应6 min时，吸附作用对TOC的去除率为43.4%，而ACF协同O₃作用时的TOC去除率提高到72.5%，协同增效作用为67.1%；在选定的反应条件下，ACF协同O₃降解焦化废水生物处理尾水，60 min时的TOC与色度的去除率分别达到56.8%和96.3%。上述研究过程证明了吸附作用与催化作用的协同能有效降解生物过程不能降解的焦化废水中惰性有机污染物。     

Capability of novel ZnFe₂O₄ nanotube arrays for visible-light induced degradation of 4-chlorophenol

Highly ordered ZnFe₂O₄ nanotube arrays were successfully prepared by anodic aluminum oxide templates from sol-gel solution. The results from environmental scanning electron microscopy and X-ray photoemission spectroscopy indicated that the as-prepared samples were vertically aligned spinel ZnFe₂O₄ nanotube arrays, and the nanotubes were uniform along the axial direction with an average diameter of approximately 200 nm. The absorption edge of ZnFe₂O₄ nanotube arrays shifted to a higher energy in the UV-Vis absorption spectrum compared with that of ZnFe₂O₄ nanoparticles film. The synthesized ZnFe₂O₄ nanotube arrays exhibited excellent photocatalytic capability for degradation of 4-chlorophenol under visible-light irradiation. The main intermediate degradation species of 4-chlorophenol identified by liquid chromatography-mass technique were benzoquinone, hydroquinone, hydroxybenzoquinone and 2-peroxy-o-dihydroxybenzene. The degradation pathways of 4-chlorophenol under visible-light irradiation was derived and discussed by interpreting the observations of the intermediate species in the photocatalytic reactions.     

Acute oral toxicity and liver oxidant/antioxidant stress of halogenated benzene, phenol, and diphenyl ether in mice: a comparative and mechanism exploration

The lethal doses (LD₅₀s) of fluorinated, chlorinated, brominated, and iodinated benzene, phenol, and diphenyl ether in mice were ascertained respectively under the consistent condition. The acute toxicity of four benzenes orders in fluorobenzene (FB)?<?iodobenzene?<?chlorobenzene≈bromobenzene, that of four phenols orders in 4-iodophenol≈4-bromophenol?<?4-chlorophenol (4-MCP)?<?4-fluorophenol (4-MFP), and that of four diphenyl ethers orders in 4,4′-iododiphenyl ether?<?4,4′-difluorodiphenyl ether?<?4,4′-dichlorodiphenyl ether≈4,4′-dibromodiphenyl ether. General behavior adverse effects were observed, and poisoned mouse were dissected to observe visceral lesions. FB, 4-MCP, and 4-MFP produced toxic faster than other halogenated benzenes and phenols, as they had lower octanol–water partition coefficients. Pathological changes in liver and liver/kidney weight changes were also observed. Hepatic superoxide dismutase, catalase activities, and malondialdehyde level were tested after a 28-day exposure, which reflects a toxicity order basically consistent with that reflected by the LD₅₀s. By theoretical calculation and building models, the toxicity of benzene, phenol, and diphenyl ether were influenced by different structural properties.     

Characterization of phenol degradation by high-efficiency binary mixed culture

Background, aim, and scope  

Two new high phenol-degrading strains, Micrococcus sp. and Alcaligenes faecalis JH 1013, were isolated. The two isolates could grow aerobically in mineral salts medium containing phenol as a sole carbon source at concentration of 3,000 mg L⁻¹. It was found that the binary mixed culture of the two isolates possessed good potential for phenol removal.     

The response of soil Arthrobacter agilis lush13 to changing conditions: Transition between vegetative and dormant state

This work was aimed at studying the response of soil non-spore-forming actinobacterial strain Arthrobacter agilis Lush 13 to changing natural conditions, such as nutrient availability and the presence of degradable and recalcitrant aliphatic and aromatic substrates. The A. agilis strain Lush13 was able to degrade octane, nonane, hexadecane, benzoate, phenol, and 2,3-, 2,4-, 2,5-, 2,6-dichlorophenols, but not grew on 3,4-dichlorophenol, 2,3,4-, 2,4,5-, 2,4,6-trichlorophenol (TCP), pentachlorophenol (PCP), 2-chlorobenzoate, 3-chlorobenzoate, 3,5-dichlorobenzoate, 2,4-dichlorobenzoate. Under growth-arresting conditions due to nitrogen- or multiple starvation or recalcitrant (non-utilizable) carbon source, the studied strain preserved viability for prolonged periods (4–24 months) due to transition to dormancy in the form of conglomerated small and ultrasmall cyst-like dormant cells (CLC). Dormant cells were shown to germinate rapidly (30 min or later) after removal of starvation stress, and this process was followed by breakdown of conglomerates with the eliberation and further division of small multiple actively growing daughter cells. Results of this study shed some light to adaptive capabilities of soil arthrobacters in pure and polluted environments.     

Titania-supported silver-based bimetallic nanoparticles as photocatalysts

Photocatalytic process has shown recently a great potential as an environmental friendly and clean remediation technology for organic pollutants in wastewater. This work described the synthesis of silver-based bimetallic nanoparticles using colloid chemistry and the subsequent immobilization onto titania to form composite photocatalytic materials (titania-supported Ag–Pt nanoparticles). The photocatalysts were characterized by X-ray diffraction, electron microscopy, and nitrogen physisorption. The catalytic activity of the photocatalysts was evaluated by photocatalytic degradation of phenol and 2-chlorophenol (2-CP) in synthetic wastewater solutions. The photocatalytic processes were conducted in a batch photoreactor containing appropriate solutions of phenol and 2-CP with UV irradiation of 450 W. UV-visible spectrophotometer was used for analyzing the concentration of phenol and 2-CP in solutions. Parameters affecting the photocatalytic process such as the solution pH, phenol and 2-CP concentrations, and catalyst concentration were investigated. The results obtained revealed that TiO₂-supported Ag/Pt nanoparticles showed a higher activity for UV-photocatalytic degradation of both phenol and 2-CP pollutants in the solution (as compared to the plain rutile TiO₂). The photodegradation processes were optimized by the 0.5-g/L catalyst with a pollutant concentration of 50 mg/L for all the samples. Complete degradation for both phenol and 2-CP was achieved after 120 min.     

Laboratory and field evidence of the photonitration of 4-chlorophenol to 2-nitro-4-chlorophenol and of the associated bicarbonate effect

Background, aim and scope  

Photochemical processes can decontaminate the aqueous environment from xenobiotics, but they also produce secondary pollutants. This paper presents field and laboratory evidence of the transformation of 4-chlorophenol (4CP) into 2-nitro-4-chlorophenol (2N4CP).     

Isolation and characteristics of sulfentrazone-degrading bacteria

This study aimed to isolate and characterize bacteria able to use sulfentrazone in the commercial formulation as their sole carbon source. The isolation of the potential sulfentrazone-degrading bacteria was made from soil samples with a recent history of herbicide application and from isolates identified through rDNA sequencing. Subsequently, we assessed the growth of the isolates and their sulfentrazone degradation ability using high-performance liquid chromatography. Twenty-six potential sulfentrazone-degrading bacterial isolates were obtained in pure culture. Through analysis of the rDNA sequences, the predominance of bacterial species of the genus Pseudomonas was found. The isolates presented a differentiated ability of sulfentrazone degradation. The presence of herbicide in the culture medium reduced the log phase of four isolates. Pseudomonas putida, Pseudomonas lutea, Pseudomonas plecoglossicida and three isolates of Pseudomonas sp. showed higher sulfentrazone degradation capacity, which varied from 4 to 15%. This is the first report of the Pseudomonas genre capable of sulfentrazone degradation. The isolates obtained present potential use in bioremediation programs for soil contaminated with sulfentrazone.     

Biodegradation of dimethylphenols by bacteria with different ring-cleavage pathways of phenolic compounds

The biodegradation of 3,4, 2,4, 2,3, 2,6 and 3,5-di-methylphenol in combination with phenol andp-cresol by axenic and mixed cultures of bacteria was investigated. The strains, which degrade phenol andp-cresol through different catabolic pathways, were isolated from river water continuously polluted with phenolic compounds of leachate of oil shale semicoke ash heaps. The proper research of degradation of 2,4 and 3,4-di-methylphenol in multinutrient environments was performed. The degradation of phenolic compounds from mixtures indicated a flux of substrates into different catabolic pathways. Catechol 2,3-dioxygenase activity was induced by dimethylphenols inPseudomonas mendocina PC1, wheremeta cleavage pathway was functional during the degradation ofp-cresol. In the case of strains PC18 and PC24 ofP. fluorescens, the degradation ofp-cresol occurred via the protocatechuateortho pathway and the key enzyme of this pathway,p-cresol methylhydroxylase, was also induced by dimethylphenols. 2,4 and 3,4-dimethylphenols were converted into the dead-end products 4-hydroxy-3-methylbenzoic acid and 4-hydroxy-2-methylbenzoic acid. In the degradation of 3,4-dimethylphenol, the transient accumulation of 4-hydroxy-2-methylbenzaldehyde repressed the consumption of phenol from substrate mixtures. A mixed culture of strains with different catabolic types made it possible to overcome the incompatibilities at degradation of studied substrate mixtures.