Isolation of Biphenyl and Polychlorinated Biphenyl-Degrading Bacteria and Their Degradation Pathway

Four strains of biphenyl-degrading bacteria were isolated from a sewage and identified from the Rhodococcus genus (SK-1, SK-3, and SK-4) and Aquamicrobium genus (SK-2) by 16S rRNA sequence. Among these strains, strain SK-2 was most suitable for biphenyl degradation. When 0.65, 1.3, 2.6, or 3.9 mM of biphenyl was used, the biphenyl was completely degraded within 24 and 96 h of culture, respectively. However, in the case of 6.5 and 9.75 mM of biphenyl, the biphenyl degradation yields were about 80 % and 46.7 % after 120 h of culture, respectively. The isolated strains could degrade a broad spectrum of aromatic compounds including high-chlorinated polychlorinated biphenyl (PCB) congeners in the presence of biphenyl. In addition, strain SK-2 could utilize PCB congeners containing one to six chlorine substituents such as 2,2′,4,4′,5,5′-hexachlorobiphenyl. The PCB utilization rate by the strain SK-2 was increased compared to that of other PCB congener-utilizing bacteria. The four isolates metabolized 4-chlorobiphenyl to 4-chlorobenzoic acid and 2-hydroxy-6-oxo-6-(4′-chlorophenyl)-hexa-2,4-dienoic acid. These results suggest the isolated strains might be good candidates for the bioremediation of PCB-contaminated soil, especially high-saline soils.     

Dissemination of catabolic plasmids among desiccation-tolerant bacteria in soil microcosms

The dissemination of catabolic plasmids was compared to bioaugmentation by strain inoculation in microcosm experiments. When Rhodococcus erythropolis strain T902, bearing a plasmid with trich loroethene and isopropylbenzene degradation pathways, was used as the inoculum, no transconjugant was isolated but the strain remained in the soil. This plasmid had a narrow host range. Pseudomonas putida strain C8S3 was used as the inoculum in a second approach. It bore a broad host range conjugative plasmid harboring a natural transposon, RP4∶Tn4371, responsible for biphenyl and 4-chlorobiphenyl degradation pathways. The inoculating population slowly decreased from its original level (10⁶ colony-forming units [CFU]/g of dry soil) to approx 3×10² CFU/g of dry soil after 3 wk. Transconjugant populations degrading biphenyl appeared in constant humidity soil (up to 2×10³ CFU/g) and desiccating soil (up to 10⁴ CFU/g). The feasibility of plasmid dissemination as a bioaugmentation technique was demonstrated in desiccating soils. The ecologic significance of desiccation in bioaugmentation was demonstrated; it upset the microbial ecology and the development of transconjugants.     

Study of the Process and Mechanism of the Remediation of Phenol Contaminated Soil by Plasma Vibrated Bed

Soil pollution is an important problem. The organic components of soil pollution are complex, and pose a significant threat to human health. In this work, a low-temperature plasma vibrated bed is applied to remediation of soil polluted by organics, with attention focused on phenol as a model pollutant. In the experiment, many factors of phenol degradation are studied and determined, such as discharge voltage, carrier gas, and soil moisture content. Increasing vibration frequency, decreasing electrode spacing, increasing voltage and a weakly alkaline soil are conducive to the degradation of pollutants. Air and oxygen give better degradation than nitrogen. The active particles generated in the discharge, such as ·OH, H₂O₂ and O₃, are shown to play an important role in degradation of phenol. In addition, maleic acid and oxalic acid are found as intermediate product during the process of phenol degradation. Furthermore, according to the qualitative and quantitative analysis of phenol degradation products, the degradation mechanism diagram of phenol in soil is drawn up, which is instructive to improve the performance of the plasma vibrated bed in the future research.     

Dimethyl disulphide residue analysis and degradation kinetics determination in soil using gas chromatography–mass spectrometry

Dimethyl disulphide (DMDS) is a volatile sulphur compound and is used as a new type of soil fumigant. The objective of this study was to develop an effective method to extract and analyse DMDS residue in soil, then determine the degradation kinetics of DMDS in soil using the above method. The results showed that DMDS extraction from soil by ethyl acetate under static conditions for 60 min gave the best recovery. The extracted DMDS was analysed by gas chromatography–mass spectrometry (GC-MS), and the limit of quantification of DMDS in the soil was 5 μg/kg. The average recoveries of the DMDS at five different concentrations were in the range of 65.4–120.1% with all intra- and inter-day relative standard deviation less than 19.1 and 14.8, respectively. The degradation rates of DMDS in different soils were significantly different and were strongly influenced by the soil pH. The results in the present study will be useful for DMDS environmental behaviour study in future.     

Biodesulfurization of a System Containing Synthetic Fuel Using Rhodococcus erythropolis ATCC 4277

The burning of fossil fuels has released a large quantity of pollutants into the atmosphere. In this context, sulfur dioxide is one of the most noxious gas which, on reacting with moist air, is transformed into sulfuric acid, causing the acid rain. In response, many countries have reformulated their legislation in order to enforce the commercialization of fuels with very low sulfur levels. The existing desulfurization processes cannot remove such low levels of sulfur and thus a biodesulfurization has been developed, where the degradation of sulfur occurs through the action of microorganisms. Rhodococcus erythropolis has been identified as one of the most promising bacteria for use in the biodesulfurization. In this study, the effectiveness of the strain R. erythropolis ATCC 4277 in the desulfurization of dibenzothiophene (DBT) was evaluated in a batch reactor using an organic phase (n-dodecane or diesel) concentrations of 20, 80, and 100 % (v/v). This strain was able to degrade 93.3, 98.0, and 95.5 % of the DBT in the presence of 20, 80, and 100 % (v/v) of dodecane, respectively. The highest value for the specific DBT degradation rate was 44?mmol DBT?·?kg DCW^?1?·?h^?1, attained in the reactor containing 80 % (v/v) of n-dodecane as the organic phase.     

Biodegradation of Crude Oil by a Newly Isolated Strain Rhodococcus sp. JZX-01

A highly efficient oil-degrading bacteria JZX-01 was isolated from the oil-contaminated soil of the seacoast near the Boxi Offshore Oil Field of China. Morphological, physiological, and 16S rDNA gene sequence analyses indicated that JZX-01 was assigned to the genus Rhodococcus sp. This strain decomposed 65.27?±?5.63 % of the crude oil in 9 days. Gas chromatography–mass spectrometry analysis showed that even the long-chain hydrocarbons (C31–C38) and branched alkanes (pristine and phytane), which were regarded as the stubborn ones, could be degraded. Further study showed that the bacteria still has good oil degradation ability at low temperatures as well as under high salt conditions. Moreover, JZX-01 was found to have a biosurfactant-producing capacity, which significantly favors the surface tension reduction and crude oil degradation. The promising isolated strain Rhodococcus sp. JZX-01 could be further used for the bioremediation of oil-polluted soil or seawater in a wide range of temperatures and high salt conditions.     

Utilization of sol–gel ceramics for the immobilization of living microorganisms

Two possible methods are described for using sol–gel technology to immobilize living microorganisms, either embedding the cells within thin silica layers, or using the technique of freeze-gelation to immobilize microorganisms within molded ceramic parts. The preparation and structure of both biocer variants are outlined, and examples are given for the activity and storage stability of embedded microorganisms. Silica layers were used to immobilize various bacteria and algae. Survival rates after storage are given for Pseudomonas fluorescence bacteria and for green algae such as H. pluvialis, C. vulgaris, B. braunii and N. limnetica embedded within thin transparent silica layers. The bioactivity of bacteria immobilized in freeze-gelation ceramics was investigated by monitoring glucose consumption for P. fluorescens NCIMB 11764, and phenol degradation for Rhodococcus ruber.     

Assessment of Acrylamide Degradation Potential of Pseudomonas aeruginosa BAC-6 Isolated from Industrial Effluent

Acrylamide finds diverse industrial applications but is considered an environmental threat because of its neurotoxic, carcinogenic, and teratogenic effects. Certain bacteria enzymatically degrade acrylamide to acrylic acid and ammonia. The present investigation was carried out to isolate and identify an acrylamide-degrading bacterium from industrial effluent. Bacterial growth and extent of acrylamide degradation in the presence of different acrylamide concentrations, nutrients, varied range of pH, and temperature were analyzed. Among the eight acrylamide-degrading isolates, isolate BAC-6 demonstrated the highest degradation, and based upon the partial 16S rDNA sequencing, it was identified as Pseudomonas aeruginosa. P. aeruginosa BAC-6 grew over a wide range of acrylamide concentrations, but the highest degradation was recorded at 500 mg/L concentration with concomitant cell growth. Among the carbon supplements, mannitol supported the highest growth and degradation. Maximum degradation was reported at neutral pH. A mesophilic temperature range (25–40 °C) facilitated conducive bacterial growth followed by degradation. The highest degradation and bacterial growth were observed at 30 and 35 °C, respectively. Thus, it could be inferred from the present investigation that cultural conditions strongly affected the degradation potential of P. aeruginosa BAC-6 and advocated the utilization of the isolate in bioremediation of sites polluted with acrylamide.     

Removal of Model Pollutants in Aqueous Solution by Gliding Arc Discharge: Determination of Removal Mechanisms. Part I: Experimental Study

The respective roles of short and long-life oxidant species in the degradation of model organic pollutants in water have been investigated in a gas–liquid gliding arc plasma reactor. Three different model pollutants were treated in two configurations: direct discharge mode and spatial post discharge mode. In each case the pollutants were classified according to their ease of removal, from easier to more difficult to remove. The results were as follows: phenol >> 1-heptanol >> pCBA. The removal mechanisms also are different depending on the characteristics of the pollutant treated. Phenol (100 % of phenol was removed for energy density = 1.20 × 10⁵ J/L) was supposed to react strongly with NO₂° radicals produced by the dissociation of N₂O₄ in liquid phase. The degradation of 1-heptanol would proceed by desorption of the liquid phase to the gas phase, where oxidation occurs due to the plasma active short-lived species. In the case of pCBA, oxidation occurs in the liquid solution, but the degradation is low because of its low reactivity with species such as ozone and °NO₂ and insufficient production of OH° radicals in the solution.     

Application of Pyrolysis Cryogenic Trap Gas Chromatography/Atomic Emission Detection (Py-CryT-GC/AED) for the Study of Nitrogen Forms and Dynamics in a Grassland Soil

Soil organic nitrogen (N) was characterized for its chemical species and chemical transformations in a grassland soil profile by using a combination of cryogenic pyrolysis gas chromatography atomic emission detection method with soil physical size fractionation. The soils taken from 0–12, 12–25, and 25–38 cm depth layers were separated into five fractions, <2, 2–38, 38–53, 53–105, and 105–250 µm and each of which was analyzed for total organic C and N, and different N forms. Our results showed that (1) total organic carbon has a positive correlation with the total organic nitrogen (TON) with correlation coefficient increased with soil depth; (2) deep and small particle-size fraction soils yielded more volatile pyrolysate N than the surface and large particle-size fractions and the amount of volatile pyrolysate N has a linear positive correlation with TON and correlation coefficient increased with soil depth; (3) the major components of the volatile pyrolysate N include ammonia, acetonitrile, hydrogen cyanide, pyridine, and pyrrole; (4) of the total volatile pyrolysate N, ammonia accounted for more than 40%, and the sum of acetonitrile and hydrogen cyanide accounted for approximately 30–50%; and (5) the amounts of acetonitrile, hydrogen cyanide, and pyridine had increased positive correlations with TON with increasing soil depth, but the correlation between the amount of pyrrole and depth decreased in the opposite direction. Our research result sheds some light into soil organic nitrogen forms and its transformations in the processes of soil organic C aging and stabilization.     

Curing the Plasmid pMC1 from the Poly (γ-glutamic Acid) Producing Bacillus amyloliquefaciens LL3 Strain Using Plasmid Incompatibility

Bacillus amyloliquefaciens LL3 is a glutamate-independent poly-γ-glutamic acid (γ-PGA) producing strain which consists of a circular chromosome (3,995,227 bp) and an endogenous plasmid pMC1 (6,758 bp). The study of the function of native plasmid and the genome-size reduction of the B. amyloliquefaciens LL3 strain requires elimination of the endogenous plasmid. Traditional plasmid-curing procedures using sodium dodecyl sulfate (SDS) or acridine orange combined with heat treatment have been shown to be ineffective in this strain. Plasmid incompatibility is an effective method for curing which has been studied before. In our research, the hypothetical Rep protein gene and the origin of replication of the endogenous plasmid were cloned into the temperature-sensitive vector yielding the incompatible plasmid pKSV7-rep-ori. This plasmid was transformed into LL3 by electroporation. The analysis of the strain bearing incompatible plasmids after incubation at 30 °C for 30 generations showed the production of plasmid cured strains. High frequency of elimination was achieved with more than 93 % of detected strains showing to be plasmid-cured. This is the first report describing plasmid cured in a γ-PGA producing strain using this method. The plasmid-cured strains showed an increase of γ-PGA production by 6 % and led to a yield of 4.159 g/l, compared to 3.918 g/l in control and cell growth increased during the early stages of the exponential phase. Gel permeation chromatography (GPC) characterization revealed that the γ-PGA produced by plasmid-cured strains and the wild strains were identical in terms of molecular weight. What is more, the further study of plasmid function showed that curing of the endogenous plasmid did not affect its sporulation efficiency.     

Occurrence of neonicotinoids in guttation liquid of maize – soil mobility and cross-contamination

Movement of clothianidin (CLO) and thiamethoxam (TMX) applied as maize seed dressing or pre-emergence spray application was determined in different soil types. Uptake of these neonicotinoids in plants emerging from coated or non-coated seeds was characterised via guttation liquid measurements. Applied in spray at a recommended dosage of 16.5 µmol/L, TMX and CLO occurred in the guttation liquid at peak concentrations of 1.82 and 1.63 mg/L, respectively, in plants in sandy soil and at 20–40% lower levels in plants in clay or loam soils. Peak emergence was substantially higher (above 100 mg/L) in the guttation liquid of plants emerging from neonicotinoid-coated seeds at dosages of 4.87 and 2.07 µmol per seed for CLO and TMX, respectively, strongly influenced by soil type. CLO and TMX levels in plants emerging from non-coated seeds in the proximity of neonicotinoid-coated seeds were demonstrated: cross-contamination may occur by uptake through soil from neighbouring plants. CLO appeared in the guttation liquid of plants emerging from non-coated seeds in proximity to coated ones at a peak concentration (approximately 53 mg/L) in 15 days corresponding to one-fifth of the levels in plants emerging from CLO-coated seeds; CLO concentrations gradually decreased to the same levels (6.6 ± 0.3 mg/L) after 24 days. A similar trend was observed for non-coated seeds near TMX-coated ones, with a gradual increase of TMX in 17–18 days, the levels in the guttation liquid of plants emerged from non-coated seeds (approximately 123 mg/L) corresponding to two-thirds of the levels in plants emerging from TMX-coated seeds. TMX concentrations dropped to the same levels in plants emerging from non-coated and coated seeds by day 20, and CLO occurred as a metabolite. To our knowledge, this is the first scientific record of neonicotinoid levels in guttation liquid of plants emerged from non-coated maize seeds.     

Dissipation of trinexapac-ethyl and its metabolite in wheat field ecosystems and microbial degradation in soil

To investigate the dissipation rate of trinexapac-ethyl and trinexapac in wheat ecosystem, field and microbial degradation experiments were designed and conducted. A simple and time-efficient analytical method for the determination of trinexapac-ethyl and trinexapac in wheat kernels, plants, straw and soil, using high-performance liquid chromatography–tandem mass spectroscopy (HPLC–MS/MS) was developed. The mean recoveries of trinexapac-ethyl and trinexapac in four matrices at three spiking levels ranged from 72.0% to 108.2%, and the relative standard deviation (RSD) ranged from 2.1% to 11.0%. In supervised field trials, the half-lives of trinexapac-ethyl in the plants were 0.93 and 2.36 d in Shandong and Tianjin, respectively; and those of trinexapac in soil and plants were 1.66 and 1.45 d in Shandong and 2.32 and 1.74 d in Tianjin. In microbial degradation experiment, the results show that the soil microbial communities have effects on their dissipation in the time scale employed.     

Phytochemical components,total phenol and mineral contents and antioxidant activity of six major medicinal plants from Rayen,Iran

The aim of this work was to evaluate the phytochemical components, minerals, the antioxidant activity and total phenol contents of the essential oil from aerial parts of six major medicinal plants in Rayen, Iran. The plants included Ranunculus arvensis, Teucrium polium, Dracocephalum polychaetum, Kelussia odoratissima, Artemisia sieberi and Thymus kotschyanus. Total phenol content ranged from 0.03 to 0.158 mg/mL. A. sieberi showed the highest radical scavenging ability (IC₅₀ = 94 μg/mL). The amount of minerals ranged as follows: P (0.23–29%), K (1.08–4.76%), Ca (0.78–2.35%), Mg (0.24–0.94%), Cu (8.3–15 mg/kg), Cd (0.7–1.1 mg/kg), Pb (2–11.7 mg/kg) and Fe (250–1280 mg/kg). A total of 79 compounds were identified across all plants. The main components studied in the plants were l-perillaldehyde, biosol, carvacrol, 1,8-cineol, terpinyl acetate and 1,2,3,6,7,7 a-hexahydro-5 h-inden 5-one.     

Concentration of arsenic in soil samples collected around the monazite processing facility, Thailand

Arsenic (As) in soil is a contaminant originated from human activities including pesticide use, mining and ore processing operations. In this work, As concentration in soil samples collected around the monazite processing facility, Pathum Thani, Thailand, was investigated. The collections of 24 soil samples were collected from the monazite processing area and 7 soil samples were collected from the control area without the processing activity of the same facility. Soils were digested with the mixture of HNO₃, HClO₄ and HF using a microwave digester. Inductively coupled plasma mass spectrometer (ICP-MS) equipped with an octopole reaction system (ORS) was used to determine the concentration of As in soils after the acid digestion. JB-3 (igneous rock) was the standard reference material used to check the accuracy of the method. It was found that the analytical results showed good agreement with the certified values. As concentration in soils collected from the monazite processing area ranged from 3.85 to 36.01 mg kg^?1 with the mean of 13.06 mg kg^?1. The concentration of As higher than the US EPA cancer soil screening level (22 mg kg^?1) was observed for only one sample. The control area showed As concentration varied from 9.59 to 14.19 mg kg^?1 with the mean of 11.97 mg kg^?1. The obtained results from this work were compared with the contaminated soil data of Amphoe Ron Phibun, Nakhon Si Thammarat, Thailand.     

Performances of Lactobacillus brevis for Producing Lactic Acid from Hydrolysate of Lignocellulosics

Utilizing all forms of sugars derived from lignocellulosic biomass via various pretreatment and hydrolysis process is a primary criterion for selecting a microorganism to produce biofuels and biochemicals. A broad carbon spectra and potential inhibitors such as furan, phenol compounds and weak acids are two major obstacles that limited the application of dilute-acid hydrolysate of lignocellulosics in lactic acid fermentation. Two strains of bacteria isolated from sour cabbage, S3F4 (Lactobacillus brevis) and XS1T3-4 (Lactobacillus plantrum), exhibited the ability to utilize various sugars present in dilute-acid hydrolysate of biomass. The S3F4 strain also showed strong resistance to potential fermentation inhibitors such as ferulic acid and furfural. Fermentation in flasks by this strain resulted in 39.1 g/l of lactic acid from dilute acid hydrolysates of corncobs that had initial total sugar concentration of 56.9 g/l (xylose, 46.4 g/l; glucose, 4.0 g/l; arabinose, 6.5 g/l). The hydrolysate of corncobs was readily utilized by S3F4 without detoxification, and the lactic acid concentration obtained in this study was higher compared to other reports.     

Simultaneous Determination of Pyridine-Triphenylborane Anti-Fouling Agent and Its Degradation Products in Artificial Seawater by CZE

We developed a CZE method for simultaneous determination of pyridine-triphenylborane (PTPB) anti-fouling agent and its degradation products such as diphenylborinic acid (DPB), phenylboronic acid (MPB), and phenol in artificial seawater (ASW) with no extraction procedure. The ASW samples, in which 20 % (v/v) acetonitrile was added, were injected directly into the capillary using vacuum injection. As the background electrolyte, 60 mM sodium tetraborate adjusted to pH 9.8 was used. The LODs (S/N = 3) for PTPB, DPB, MPB, and phenol were, respectively, 55, 78, 126, and 30 μg L^?1. The RSDs (n = 4) for analytes listed above were in the respective ranges of 2.7–5.7, 0.68–6.1, and 0.69–1.1 % for the peak area, peak height, and migration time. Simple degradation experiments were conducted to verify the usefulness of the proposed method. The PTPB samples dissolved in ASW were put in the open air, and rooms with and without light. The sample solutions were analyzed over time. We inferred that PTPB in ASW was more degraded by photolysis than by hydrolysis. The proposed CZE method has been demonstrated as a useful tool to elucidate the PTPB degradation process and its degradation products in ASW.     

Biodegradation of organophosphorus insecticide chlorpyrifos into a major fuel additive 2,4-bis(1,1 dimethylethyl) phenol using white-rot fungal strain Trametes hirsuta MTCC-1171

Biodegradation of chlorpyrifos, a widely used organophosphorus insecticide, was accomplished by using a white-rot fungal strain (Trametes hirsuta MTCC-1171). The experimental results showed that the fungal strain can effectively and rapidly degrade chlorpyrifos while using it as a sole source of carbon and energy when provided with mineral salt medium (MSM). The optimum experimental conditions for degradation of chlorpyrifos in liquid media can be summed as follows: initial pH 6.0; mycelial inoculum 0.18 ​± ​0.01 ​g ​L⁻¹ (dry weight); chlorpyrifos concentration 150 ​mg ​L⁻¹; pH 6.0; temperature 30 ​°C; and shaking speed 150 ​rpm. Under these optimal experimental parameters, T. hirsuta MTCC-1171 achieved ≥95% degradation of chlorpyrifos in 16 ​h of incubation. The degradation rate was quantified by employing HPLC followed by identification of degradation metabolites using gas chromatography–mass spectrometry (GC-MS). 2,4-Bis (1,1 dimethylethyl) phenol, a fuel additive, was found to be a major metabolite product of chlorpyrifos degradation. However, no metabolite bioaccumulation was observed in the process. Additionally, soil studies were carried out to investigate the degradation ability of the strain against chlorpyrifos, in a natural environment. During the assessment 37 ​± ​2.3% degradation was observed after 15 days of incubation. These results illustrate that T. hirsuta MTCC-1171 has a potential of using chlorpyrifos as a sole source of carbon. Besides, fundamental understanding gained through this work lays a foundation to investigate efficient and rapid bioremediation processes in agricultural and forest environments.     

Simultaneous Determination of Pyridine-Triphenylborane Anti-Fouling Agent and Its Degradation Products in Artificial Seawater by CZE

We developed a CZE method for simultaneous determination of pyridine-triphenylborane (PTPB) anti-fouling agent and its degradation products such as diphenylborinic acid (DPB), phenylboronic acid (MPB), and phenol in artificial seawater (ASW) with no extraction procedure. The ASW samples, in which 20 % (v/v) acetonitrile was added, were injected directly into the capillary using vacuum injection. As the background electrolyte, 60 mM sodium tetraborate adjusted to pH 9.8 was used. The LODs (S/N = 3) for PTPB, DPB, MPB, and phenol were, respectively, 55, 78, 126, and 30 μg L⁻¹. The RSDs (n = 4) for analytes listed above were in the respective ranges of 2.7–5.7, 0.68–6.1, and 0.69–1.1 % for the peak area, peak height, and migration time. Simple degradation experiments were conducted to verify the usefulness of the proposed method. The PTPB samples dissolved in ASW were put in the open air, and rooms with and without light. The sample solutions were analyzed over time. We inferred that PTPB in ASW was more degraded by photolysis than by hydrolysis. The proposed CZE method has been demonstrated as a useful tool to elucidate the PTPB degradation process and its degradation products in ASW.