Long-term comparison of the performance of biostimulation and phytoextraction in soil contaminated with diesel and heavy metals.

The long-term remediation performance under the natural conditions is required to establish the appropriate remediation strategy for contaminated soil. The objective of this study was to compare the long-term remediation efficiency of biostimulation and phytoextraction in contaminated soil containing petroleum hydrocarbons (PHs) and heavy metals. Two types of contaminated soil (soil contaminated with diesel only and co-contaminated with diesel and heavy metals) were prepared. For the biostimulation treatments, the soil was amended with compost, whereas maize, a representative phytoremediation plant, was cultivated for the phytoextraction treatments. There was no significant difference in remediation performance of biostimulation and phytoextraction in the diesel-contaminated soil, in which the maximum total petroleum hydrocarbon (TPH) removability was 94-96% (p < 0.05). However, phytoextraction exhibited the higher removability for TPH and heavy metals than biostimulation in the co-contaminated soil. There was no considerable change in the TPH removal in biostimulation (16-25%), while phytoextraction showed a 75% of TPH removal rate in the co-contaminated soil. Additionally, no significant changes were observed in heavy metals concentration of biostimulation, whereas the removability of heavy metals was 33-63% in phytoextraction. Meanwhile, maize, which is a suitable plant for phytoextraction, showed a translocation factor (translocating efficiency from roots to shoots) value of >1. Correlation analysis revealed that soil properties (pH, water content, and organic content) negatively correlated with pollutants removal. Additionally, the soil bacterial communities were changed over the investigated period, and the types of pollutants exerted a significant influence on the bacterial community dynamics. This study performed a pilot-scale comparison of two types of biological remediation technologies under natural environmental conditions and provided information on changes in the bacterial community structures. This study can be useful for establishing appropriate biological remediation methods to restore soil contaminated with PHs and heavy metals.

Seasonal Dynamics of Bacterial Community Structure in Diesel Oil-Contaminated Soil Cultivated with Tall Fescue (Festuca arundinacea).

The objective of this study was to explore the seasonal characteristics of rhizoremediation and the bacterial community structure over the course of a year in soil contaminated with diesel oil. The soil was contaminated with diesel oil at a total petroleum hydrocarbon (TPH) concentration of 30,000 mg-TPH·kg-soil-1. Tall fescue seedlings were planted in the contaminated soil and rhizoremediation performance was monitored for 317 days. The TPH concentration gradually declined, reaching 75.6% after day 61. However, the TPH removability decreased by up to 30% after re-contamination in the fall and winter. The bacterial community structure exhibited distinct seasonal dynamics. Genus Pseudomonas significantly increased up to 55.7% in the winter, while the genera Immundisolibacter and Lysobacter, well-known petroleum hydrocarbon (PH)-degrading bacteria, were found to be positively linked to the TPH removal rate. Consequently, knowledge of this seasonal variation in rhizoremediation performance and the bacterial community structure is useful for the improvement of rhizoremediation in PH-contaminated environments.

Dynamics of bacterial functional genes and community structures during rhizoremediation of diesel-contaminated compost-amended soil.

The objective of this study was to characterize the effects of organic soil amendment (compost) on bacterial populations associated with petroleum hydrocarbon (PH) degradation and nitrous oxide (N2O) dynamics via pot experiments. Soil was artificially contaminated with diesel oil at total petroleum hydrocarbon (TPH) concentration of 30,000 mg·kg-soil-1 and compost was mixed with the contaminated soil at a 1:9 ratio (w/w). Maize seedlings were planted in each pot and a total of ten pots with two treatments (compost-amended and unamended) were prepared. The pot experiment was conducted for 85 days. The compost-amended soil had a significantly higher TPH removal efficiency (51.1%) than unamended soil (21.4%). Additionally, the relative abundance of the alkB gene, which is associated with PH degradation, was higher in the compost-amended soil than in the unamended soil. Similarly, cnorB and nosZ (which are associated with nitric oxide (NO) and N2O reduction, respectively) were also highly upregulated in the compost-amended soil. Moreover, the compost-amended soil exhibited higher richness and evenness indices, indicating that bacterial diversity was higher in the amended soil than in the unamended soil. Therefore, our findings may contribute to the development of strategies to enhance remediation efficiency and greenhouse gas mitigation during the rhizoremediation of diesel-contaminated soils.

Effects of Plant and Soil Amendment on Remediation Performance and Methane Mitigation in Petroleum-Contaminated Soil.

Petroleum-contaminated soil is considered among the most important potential anthropogenic atmospheric methane sources. Additionally, various rhizoremediation factors can affect methane emissions by altering soil ecosystem carbon cycles. Nonetheless, greenhouse gas emissions from soil have not been given due importance as a potentially relevant parameter in rhizoremediation techniques. Therefore, in this study we sought to investigate the effects of different plant and soil amendments on both remediation efficiencies and methane emission characteristics in dieselcontaminated soil. An indoor pot experiment consisting of three plant treatments (control, maize, tall fescue) and two soil amendments (chemical nutrient, compost) was performed for 95 days. Total petroleum hydrocarbon (TPH) removal efficiency, dehydrogenase activity, and alkB (i.e., an alkane compound-degrading enzyme) gene abundance were the highest in the tall fescue and maize soil system amended with compost. Compost addition enhanced both the overall remediation efficiencies, as well as pmoA (i.e., a methane-oxidizing enzyme) gene abundance in soils. Moreover, the potential methane emission of diesel-contaminated soil was relatively low when maize was introduced to the soil system. After microbial community analysis, various TPH-degrading microorganisms (Nocardioides, Marinobacter, Immitisolibacter, Acinetobacter, Kocuria, Mycobacterium, Pseudomonas, Alcanivorax) and methane-oxidizing microorganisms (Methylocapsa, Methylosarcina) were observed in the rhizosphere soil. The effects of major rhizoremediation factors on soil remediation efficiency and greenhouse gas emissions discussed herein are expected to contribute to the development of sustainable biological remediation technologies in response to global climate change.

Effects of Chronic Intake of a Low Concentration of Taurine on Physical Strength and Body Composition in Mice.

Most studies of taurine on athletic performance have been conducted at acute and high doses in rodents. These doses and duration of administration are not reasonable for normal human life. Thus, it is not valid to extrapolate these animal results to people. Dose and duration that mimic human use of taurine in normal life can help to clarify the taurine effect in humans. This study investigated whether long-term, low-dose taurine (2% taurine drinking water for 25 weeks), similar to normal taurine intake in humans, can affect endurance exercise and body composition. Twenty ICR mice were divided into two groups. The control group received normal drinking water, and the taurine treated group received 2% taurine drinking water for 25 weeks. The mice were evaluated for body composition by mass and for physical strength by treadmill exhaustion and suspension tests. The supply of chronic 2% taurine drinking water has a slight effect on weight gain. In body composition analysis, a slight increase in body weight was due to an increase in muscle mass, not an increase in body fat. However, taurine ingestion did not increase endurance exercise. In conclusion, these results indirectly suggest that acute, high-dose taurine treatment is better than long-term, low-dose treatment to increase athletic performance.

Relationship of nutrient dynamics and bacterial community structure at the water-sediment interface using a benthic chamber experiment.

The relationships between nutrient dynamics and the bacterial community at the water-sediment interface were investigated using the results of nutrient release fluxes, bacterial communities examined by 16S rRNA pyrosequencing and canonical correlation analysis (CCA) accompanied by lab-scale benthic chamber experiment. The nutrient release fluxes from the sediments into the water were as follows: -3.832 to 12.157 mg m-2 d-1 for total phosphorus, 0.049 to 9.993 mg m-2 d-1 for PO4-P, -2.011 to 41.699 mg m-2 d-1 for total nitrogen, -7.915 to -0.074 mg m-2 d-1 for NH3-N, and -17.940 to 1.209 mg m-2 d-1 for NO3-N. To evaluate the relationship between the bacterial communities and environmental variables, CCA was conducted in three representative conditions: in the overlying water, in the sediment at a depth of 0-5 cm, and in the sediment at a depth of 5-15 cm. CCA results showed that environmental variables such as nutrient release fluxes (TN, NH4, NO3, TP, and PO4) and water chemical parameters (pH, DO, COD, and temperature) were highly correlated with the bacterial communities. From the results of the nutrient release fluxes and the bacterial community, this study proposed the hypothesis for bacteria involved in the nutrient dynamics at the interface between water and sediment. In the sediment, sulfate-reducing bacteria (SRB) such as Desulfatibacillum, Desulfobacterium, Desulfomicrobium, and Desulfosalsimonas are expected to contribute to the decomposition of organic matter, and release of ammonia (NH4+) and phosphate (PO43-). The PO43- released into the water layer was observed by the positive fluxes of PO43-. The NH4+ released from the sediment was rapidly oxidized by the methane-oxidizing bacteria (MOB). This study observed in the water layer dominantly abundant MOB of Methylobacillus, Methylobacter, Methylocaldum, and Methylophilus. The nitrate (NO3-) accumulation caused by the oxidation environment of the water layer moved back to the sediment, which led to the relatively large negative fluxes of NO3-, compared to the small negative fluxes of NH4+.

Decolorization of textile dyes in an air-lift bioreactor inoculated with Bjerkandera adusta OBR105.

A new decolorizing white-rot fungus, OBR105, was isolated from Mount Odae in South Korea and identified by the morphological characterization of its fruit body and spores and partial 18s rDNA sequences. The ligninolytic enzyme activity of OBR105 was studied to characterize their decolorizing mechanism using a spectrophotometric enzyme assay. For the evaluation of the decolorization capacity of OBR105, the isolate was incubated in an erlenmeyer flask and in an airlifte bioreator with potato dextrose broth (PDB) medium supplemented with each dye. In addition, the decolorization efficiency of real textile wastewater was evaluated in an airlift bioreactor inoculated with the isolate. The isolate was identified as Bjerkandera adusta and had ligninolytic enzymes such as laccase, lignin peroxidase (LiP), and Mn-dependent peroxidase (MnP). Its LiP activity was higher than its MnP and laccase activities. B. adusta OBR105 successfully decolorized reactive dyes (red 120, blue 4, orange 16, and black 5) and acid dyes (red 114, blue 62, orange 7, and black 172). B. adusta OBR105 decolorized 91-99% of 200 mg L-1 of each dye (except acid orange 7) within 3 days in a PDB medium at 28°C, pH 5, and 150 rpm. This fungus decolorized only 45% of 200 mg L-1 acid orange 7 (single azo-type dye) within 3 days, and the decolorization efficiency did not increase by prolonging the cultivation time. In the air-lift bioreactor, B. adusta OBR105 displayed a high decolorization capacity, greater than 90%, for 3 acid dyes (red 114, blue 62, and black 172) and 1 reactive dye (blue 4) within 10-15 h of treatment. B. adusta OBR105 could decolorize real textile wastewater in the air-lift bioreactor. This result suggests that an air-lift reactor employing B. adusta OBR105 is a promising bioreactor for the treatment of dye wastewater.

Fate and behavior of extended-spectrum ß-lactamase-producing genes in municipal sewage treatment plants.

Extended-spectrum ß-lactamases (ESBLs) have the capability of hydrolyzing a variety of the newer ß-lactam antibiotics, including the third-generation cephalosporins and monobactams known as a rapidly evolving group of ESBLs. The purpose of this study was to investigate the occurrence and fate of ß-lactamase producing genes (CTX-M type 1, type2, CTX-M probe for all groups except CTX-M-1, and TEM, SHV, OXA) through wastewater treatment utilities. ß-lactamase producing genes in influent, digested sludge, activated sludge, and disinfected effluent were monitored. The results showed that influent contained high level of all target genes, and all CTX-M types, SHV, and OXA gene decreased significantly in biological treatment process such as activated sludge process and anaerobic digestion, however, TEM type was not effectively eliminated. Possibly, host microbes of TEM could be most resistant in target genes or to some extent gene transfer occurred in wastewater treatment processes. All target genes were significantly reduced during disinfection. Consequently, wastewater treatment process apparently reduced host microbes carrying ß-lactamase producing genes effectively, although they are selectively removed in biological processes. In addition, the significant reduction during disinfection was shown, although slightly differences of removal efficiency were observed in resistance.

Biodegradation of petroleum hydrocarbons by Neosartorya sp. BL4.

A new petroleum hydrocarbon-degrading fungus, isolated from an oil contaminant soil, was identified as Neosartorya (teleomorph of Aspergillus) sp. This isolate was able to degrade total petroleum hydrocarbons (TPHs) without a lag phase, but degradation rates decreased with increasing initial TPH concentrations (5,000-20,000 mg L(-1)). The TPH degradation by the isolate showed a substrate inhibition behavior with an inhibition constant (K(i)) of 1,860 mg L(-1). Dual lag phase of TPH degradation indicated the ability to adapt its metabolic activity to utilize different types of hydrocarbons as an electron donor. Initially n-alkanes were rapidly removed without lag phase in the whole range of substrate and heavy molecular weight alkanes (HMWAs; C23-C24) and low molecular weight alkanes (LMWAs C9-C15) out of n-alkane hydrocarbons were degraded rapidly, whereas the removal of mid molecular weight alkanes (MMWAs; C16-C22) was relatively slower. Relatively slow degradation of MMWAs is probably caused by biotransformation of HMWAs or non-alkane hydrocarbons to MMWAs.

Bacterial diversity dynamics in a long-term petroleum-contaminated soil.

Bacterial diversity dynamics were investigated in the soil samples in different distances and depths from/at a long-term petroleum-contaminated site. Microbial activity in the soil samples showed ATP values closely correlated with organic matter content (OC) and total petroleum hydrocarbon (TPH). Bacterial community diversity (H) and evenness (J) using PCR-DGGE (polymerase chain reaction-denaturing gradient gel electrophoresis) and PCR-T-RFLP (terminal restriction fragment length polymorphism) results showed positive correlation with concentration of TPH or OC, but tmoA (toluene monooxygenase gene)-based bacterial H and J using a PCR-T-RFLP result did not. No significant difference of H and J values in the bacterial and the tmoA communities was observed. The bacterial community structure characterized by PCR-DGGE and PCR-T-RFLP techniques showed similarity according to soil sampling distance rather than soil sampling depth. Canonical correspondence analysis demonstrated that OC including TPH had the most significant effect on the bacterial community diversity at the long-term petroleum-contaminated site.

Microbial recovery of copper from printed circuit boards of waste computer by Acidithiobacillus ferrooxidans.

The bioleaching of copper contained in the printed circuit boards (PCB) of waste computers by A. ferrooxidans was studied. The Fe oxidation rates by A. ferrooxidans in the 9K medium supplemented with the leachate of PCB (0.15-0.13 g L(-1) d(-1)) were similar to that in the 9K medium without the leachate (0.15 g L(-1) d(-1)). This finding suggests that the leachate of PCB did not seriously affect the bioleaching process by this bacterium. The amount of copper leached from PCB shreds increased with the addition of ferrous ion and reached up to 5190 mg L(-1) when the initial concentration of Fe2+ ion was 7 g L(-1). As the microbial leaching progressed, pale brown precipitate was observed to form in the solution. Based on the total amount of copper, both in solution and precipitate, the optimal addition of ferrous ion for the leaching of copper was around 7 g L(-1). When citric acid was not added, only about 37 wt% of the total leached copper remained dissolved; however, the amount of dissolved copper increased to greater than 80 wt% in the presence of citric acid. This fact indicates that the addition of a complexing agent (citric acid) to the bioleaching solution can raise the solubility of the leached metal ions.

Characterization of biofilms occurred in seepage groundwater contaminated with petroleum within an urban subway tunnel.

Biofilms occurring in seepage groundwater contaminated with petroleum in an urban subway drainage system were characterized. The development of biofilms was observed only in the sites where petroleum-contaminated groundwater had seeped or was seeping. Moreover, the conditions of the biofilms such as color and development extent were influenced by the amount of spilled petroleum: By increasing the amount of spilled petroleum, the amount of biofilms increased and its color whitened. It deteriorated and became dark-brown if the contaminated groundwater did not seep any more. These facts indicate that the biofilms can be used as a preliminary indicator to identify the locations of fuel contaminated sumps and seeps without a more detailed assessment such as instrumental analysis. The biofilms were capable of degrading petroleum at 15 degrees C, which is similar to the average temperature of the seepage groundwater. Filamentous bacteria, Sphaerotilus spp., were isolated from the biofilms. It is considered that these bacteria are responsible for the development of biofilms in the seepage groundwater contaminated with petroleum because they can secrete extracellular polymeric substances.