Bacterial community changes in TCE biodegradation detected in microcosm experiments

Laboratory microcosm experiments were set up to model biodegradation of trichloroethylene (TCE). Groundwater samples from two contaminated sites were taken, one of them with low (70 mg L⁻¹), the other with high sulfate (685 mg L⁻¹) concentration. In order to assess the biodegradative potential of natural microbiota, supplementary substrates (whey or molasses) were added to the bottles. At day 54, 98, 155, and 318, chemical and bacteriological parameters (i.e., Dehalococcoides test) were investigated. Terminal restriction fragment length polymorphism (T-RFLP) based diversity assessments were carried out to observe the bacterial community changes. Whey and molasses enhanced degradation at different rates. In the case of samples with high sulfate content and amended with whey, no ethylene, ethane, or methane was generated. Both ethylene and methane production was detected in samples of low sulfate content with added whey. The results of Dehalococcoides tests were positive for all control and amended samples. Based on T-RFLP analysis, the bacterial communities of high sulfate concentration groundwater microcosms amended with molasses or whey were very similar, while the communities of groundwater samples with low sulfate concentration were different when supplemented with whey or molasses. The rRNA and rDNA based investigations suggest that the proportions of the active microbes and the microbes present in the microcosms differ.     

Sulfate reduction and microbial community of autotrophic biocathode in response to acidity

Microbial electrolysis cells (MECs) with autotrophic biocathode are a promising technology for removal of pollutants in wastewater. The aim of this study was to investigate the effect of initial acidity of wastewater on performance of sulfate-reducing biocathodes. MECs with biocathodes were operated with initial pH values of catholyte ranged from 3.0 to 7.0. The optimum initial pH value was 6.0 with a maximum sulfate reductive rate and biomass of 57 mg L⁻¹ d⁻¹ and 2.1 ± 0.4 mg g⁻¹, respectively. With initial pH 7.0, the pH value of catholyte increased to 9.8 ± 0.2 after an operation cycle, which resulted in low performance of the biocathode. A considerable sulfate reductive rate of 31 ± 0.85 mg L⁻¹ d⁻¹ was achieved with initial pH 3.0. Desulfovibrio sp. grew dominantly with abundance of 46%–66% in the cathode biofilm with initial pH values from 3.0 to 6.0 and contributed to the sulfate reduction. Clostridium and Parapedobacter also had high abundance in pH 6.0 cathode, indicated that interspecies electron transfer between electrochemical active and sulfate-reducing bacteria could play an important role in sulfate removal. The results suggest that acidity of catholyte is an important factor to be considered to utilize autotrophic biocathode MECs for wastewater treatment.     

Treatment of dye (Remazol Blue) and heavy metals using yeast cells with the purpose of managing polluted textile wastewaters

The bioaccumulation of chromium(VI), nickel(II), copper(II), and reactive dye by the yeast Rhodotorula mucilaginosa has been investigated in media containing molasses as a carbon and energy source. Optimal pH values for the yeast cells to remove the pollutants were pH 4 for copper(II) and dye, pH 6 for chromium(VI) and dye, and pH 5 for nickel(II) and dye in media containing 50 mg l^?1 heavy metal and 50 mg l^?1 Remazol Blue. The maximum dye bioaccumulation was observed within 4–6 days and uptake yields varied from 93% to 97%. The highest copper(II) removal yields measured were 30.6% for 45.4 mg l^?1 and 32.4% for 95.9 mg l^?1 initial copper(II) concentrations. The nickel(II) removal yield was 45.5% for 22.3 mg l^?1, 38.0% for 34.7 mg l^?1, and 30.3% for 62.2 mg l^?1. Higher chromium(VI) removal yields were obtained, such as 94.5% for 49.2 mg l^?1 and 87.7% for 129.2 mg l^?1 initial chromium(VI) concentration. The maximum dye and heavy metal bioaccumulation yield was investigated in media with a constant dye (approximately 50 mg l^?1) and increasing heavy metal concentration. In the medium with 48.9–98.8 mg l^?1 copper(II) and constant dye concentration, the maximum copper(II) bioaccumulation was 27.7% and 27.9% whereas the maximum dye bioaccumulation was 96.1% and 95.3%. The maximum chromium(VI) bioaccumulation in the medium with dye was 95.2% and 80.3% at 48.2 and 102.2 mg l^?1 chromium(VI) concentrations. In these media dye bioaccumulation was 76.1% and 35.1%, respectively. The highest nickel(II) removal was 6.1%, 20.3% and 16.0% in the medium with 23.8 mg l^?1 nickel(II) + 37.8 mg l^?1 dye, 38.1 mg l^?1 nickel(II) + 33.4 mg l^?1 dye and 59.0 mg l^?1 nickel(II) + 39.2 mg l^?1 dye, respectively. The maximum dye bioaccumulation yield in the media with nickel(II) was 94.1%, 78.0% and 58.7%, respectively.     

Response of native grasses and Cicer arietinum to soil polluted with mining wastes: Implications for the management of land adjacent to mine sites

Mine tailings are an environmental problem in Southern Spain because wind and water erosion of bare surfaces results in the dispersal of toxic metals over nearby urban or agricultural areas. Revegetation with tolerant native species may reduce this risk. We grew two grasses, Lygeum spartum and Piptatherum miliaceum, and the crop species Cicer arietinum (chickpea) under controlled conditions in pots containing a mine tailings mixed into non-polluted soil to give treatments of 0%, 25%, 50%, 75% and 100% mine tailings. We tested a neutral (pH 7.4) mine tailings which contained high concentrations of Cd, Cu, Pb and Zn. Water-extractable metal concentrations increased in proportion to the amount of tailings added. The biomass of the two grasses decreased in proportion to the rate of neutral mine-tailing addition, while the biomass of C. arietinum only decreased in relation to the control treatment. Neutron radiography revealed that root development of C. arietinum was perturbed in soil amended with the neutral tailings compared to those of the control treatment, despite a lack of toxicity symptoms in the shoots. In all treatments and for all metals, the plants accumulated higher concentrations in the roots than in shoots. The highest concentrations occurred in the roots of P. miliaceum (2500 mg kg^?1 Pb, 146 mg kg^?1 Cd, 185 mg kg^?1 Cu, 2700 mg kg^?1 Zn). C. arietinum seeds had normal concentrations of Zn (70–90 mg kg^?1) and Cu (6–9 mg kg^?1). However, the Cd concentration in this species was ～1 mg kg^?1 in the seeds and 14.5 mg kg^?1 in shoots. Consumption of these plant species by cattle and wild fauna may present a risk of toxic metals entering the food chain.     

Molecular cloning and high-level expression of a β-galactosidase gene from Paecilomyces aerugineus in Pichia pastoris

A β-galactosidase gene (designated PaGalA) was cloned for the first time from Paecilomyces aerugineus and expressed in Pichia pastoris under the control of the AOX1 promoter. The coding region of 3036 bp encoded a protein of 1011 amino acids with a deduced molecular mass of 108.7 kDa. The PaGalA without the signal peptide was cloned into a vector pPIC9K and was expressed successfully in P. pastoris as active extracellular β-galactosidase. The recombinant β-galactosidase (PaGalA) was secreted into the medium at an extremely high levels of 22 mg ml⁻¹ having an activity of 9500 U ml⁻¹ from high density fermentation culture, which is by far the highest yield obtained for a β-galactosidase. The purified enzyme with a high specific activity of 820 U mg⁻¹ had a molecular mass of 120 kDa on SDS-PAGE. PaGalA was optimally active at pH 4.5 and a temperature of 60 °C. The recombinant β-galactosidase was able to hydrolyze lactose efficiently at pH 5.0 and 50 °C. It also possessed transglycosylation activities at high concentrations of lactose. PaGalA exhibited better lactose hydrolysis efficiency in whey than two other widely used commercial lactases. The extremely high expression levels coupled with favorable biochemical properties make this enzyme highly suitable for commercial purposes in the hydrolysis of lactose in milk or whey.     

Phosphogypsum biotransformation in cultures of sulphate reducing bacteria in whey

Assemblages of anaerobic sulphidogenic microorganisms were isolated from soil polluted by oil-derived products and grown using the microcosms method. The cultures were grown in minimal and Postgate media with phosphogypsum (PG) as the sole electron acceptor and with lactate, casein or lactose as the sole carbon source. The most effective was the assemblage in Postgate medium with lactose as the sole carbon source. A reduction of 980 mg COD l^?1 (reduction of about 40%) and 790 mg SO₄^2? l^?1 (reduction of 53% of phosphogypsum introduced to the medium) was noted in the culture. The lowest activity was observed for minimal medium with lactose as sole carbon source (reduction of 4.4% COD and 40% PG). The selected assemblage became an inoculum for a culture in Postgate, minimal and/or distilled water medium with PG (6 g l^?1) and cheese whey (2.5 and 4.5 g l^?1).A percentage reduction of COD and SO₄^2? of PG was observed in all cultures. After growth, the residues were weighed and in all cases a distinct mass reduction of PG was observed in comparison to the 6 g l^?1 introduced to the medium. Diffractometric studies of the residues confirmed the presence of calcite and apatite. The presence of these mineral phases in the residues allows their application as agricultural fertilisers.     

Influence of environmental related concentrations of heavy metals on motility parameters and antioxidant responses in sturgeon sperm

The effects of heavy metals (Cd, Cr and Cd + Cr) on the motility parameters and oxidative stress of sterlet (Acipenser ruthenus) sperm were investigated in vitro. Sturgeon sperm were exposed for 2 h to heavy metals at environmental related concentrations (0.1 mg L^?1 Cr, 0.001 mg L^?1 Cd, 0.1 mg L^?1 Cr + 0.001 mg L^?1 Cd) and higher concentrations (5.0 mg L^?1 Cr, 0.05 mg L^?1 Cd, 5.0 mg L^?1 Cr + 0.05 mg L^?1 Cd). Results revealed that environmental concentrations of heavy metals had no significant influence on motility parameters and antioxidant responses indices in sturgeon sperm, except for LPO level and SOD activity. But higher concentrations of these metals induced oxidative tress in sturgeon sperm in vitro, associated with sperm motility parameters inhibition. Our results suggest that using of sperm in vitro assays may provide a novel and efficiently means for evaluating the effects of residual heavy metals in aquatic environment on sturgeon.     

Protocorm culture of Dendrobium candidum in balloon type bubble bioreactors

Protocorm cultures of Dendrobium candidum were established in balloon type bubble bioreactors using Murashige and Skoog (MS) medium with 0.5 mg l⁻¹ α-naphthaleneacetic acid (NAA), 2.5% (w/v) sucrose, 5:25 mM NH₄:NO₃ and 1% (v/v) banana homogenate for the production of biomass and bioactive compounds. In 3 l bioreactor containing 2 l medium, a maximum protocorm biomass (21.0 g l⁻¹ dry biomass) and also optimum quantities of total polysaccharides (389.3 mg g⁻¹ DW), coumarins (18.0 mg g⁻¹ DW), polyphenolics (11.9 mg g⁻¹ DW), and flavonoids (4.5 mg g⁻¹ DW) were achieved after 7 weeks of culture. Based on these studies, 5 and 10 l bioreactor cultures were established to harvest 80 g and 160 g dry biomass. In 10 l bioreactors, the protocorms grown were accumulated with optimal levels of polysaccharides (424.1 mg g⁻¹ DW), coumarins (15.8 mg g⁻¹ DW), polyphenols (9.03 mg g⁻¹ DW) and flavonoids (4.7 mg g⁻¹ DW). The bioreactor technology developed here will be useful for the production of important bioactive compounds from D. candidum.     

Naphthalene and biphenyl oxidation by two marine Pseudomonas strains isolated from Venice Lagoon sediment

A sediment sample from Venice Lagoon was found to be contaminated with 475 mg Kg⁻¹ polycyclic aromatic hydrocarbons (PAHs). Naphthalene was the principal pollutant at 26% of total PAHs. Two strains of Pseudomonas SN1 and SB1 were isolated from sediment amended with 2% naphthalene. 16S rRNA gene sequence analysis indicated that the two strains have about 99% nucleotide identity with strains of the genus Pseudomonas, and are very close to Pseudomonas stutzeri. Their metabolic profiles showed significant nutritional differences, the most significant of which was that SN1 grows in marine mineral medium spiked with naphthalene and SB1 grows with biphenyl as sole carbon and energy sources. Pseudomonas sp. SN1 had a doubling time of 3.1 h with 2% naphthalene and SB1 had a doubling time of 19.5 h with 2% biphenyl. Strain SN1 oxidised naphthalene at 564±32 mg O₂ l⁻¹ d⁻¹ and SB1 oxidised biphenyl at 426±25 mg O₂ l⁻¹ d⁻¹ in respirometry reaction vessels under controlled conditions. Screening of the two strains for dioxygenase genes involved in the first step of the two hydrocarbon degradation pathways, by polymerase chain reaction, showed naphthalene dioxygenase in SN1 and biphenyl dioxygenase in SB1. The strains each have a different catechol 2,3-dioxygenase responsible for cleavage of the aromatic ring.     

Nitrite inhibition and intermediates effects on Anammox bacteria: A batch-scale experimental study

A batch test procedure, based on manometric measurements, was used to study the Anammox process, in particular the inhibition due to nitrite and the effects of hydroxylamine and hydrazine, indicated as possible intermediates of the process. The maximum nitrite removal rate (MNRR) was measured. The method showed good reliability with a standard error of 4.5 ± 3.3% (n: 41). All the tests were carried out on samples taken from a pilot plant with Anammox suspended biomass. The tests were used also to monitor the reactor activity. By testing different spiked additions of nitrite (10–75 mg NO₂⁻-N L⁻¹), a short-term inhibition, with more than 25% MNRR decrease, was found at concentrations higher than 60 mg NO₂⁻-N L⁻¹. Repeated additions of nitrite higher than 30 mg NO₂⁻-N L⁻¹ caused losses of activity. After a complete loss of activity, spiked additions of hydroxylamine (30 mg N L⁻¹ in total) determined a 20% permanent recovery. Low amounts of the intermediates (1–3 mg N L⁻¹) applied on partially inhibited samples and uninhibited samples produced temporary increases in activity up to 50% and 30%, respectively.     

Investigating CH4 and N2O emissions from eco-engineering wastewater treatment processes using constructed wetland microcosms

Methane (CH₄) and nitrous oxide (N₂O) are important greenhouse gases, because of their contribution to the global greenhouse effect. The present study assessed emissions of N₂O and CH₄ from constructed wetland microcosms, planted with Phragmites australis and Zizania latifolia, when treating wastewater under different biological oxygen demand (BOD) concentration conditions. The removal rate was 95% for BOD and more than 80% for COD in all three pollutant concentrations, both plants’ removal rates of pollutants were at almost the same level, and both were found to resist BOD concentrations as high as 200 mg L⁻¹. When BOD concentrations fell below 200 mg L⁻¹, the soil plant units reached an average of 80–92% T-N and T-P removal rates; however, as the concentrations increased to 200 mg mg L⁻¹ or when during the initial phases of winter, the removal rates for T-N and T-P decreased to less than 70%. With NH₃-N removal, the influences of BOD concentrations and air temperature were more obvious. When BOD concentrations increased to 100 mg L⁻¹ after October, an obvious decrease in NH₃-N removal was detected; almost no nitrification occurred beginning in December at BOD concentrations of 200 mg mg L⁻¹. N₂O and CH₄ emissions showed obvious seasonal changes; higher emissions were observed with higher BOD concentrations, especially among Z. latifolia units. The enumeration of methane-oxidizing bacteria and methane-producing bacteria was also conducted to investigate their roles in impacting methane emissions and their relationships with plant species. The pollutant purification potentials of P. australis and Z. latifolia plant units during wastewater treatment of different pollutant concentrations occurred at almost the same levels. The nutrient outflow and methane flux were consistently higher with Z. latifolia units and higher concentrations of BOD. The more reductive status and higher biomass of methanogens may be the reason for the lower nitrification and higher CH₄ emissions observed with Z. latifolia units and higher concentration systems. The Z. latifolia root system is shallow, and the activity of methanotrophs is primarily confined to the upper portion of the soil. However, the root system of P. australis is deeper and can oxidize methane to a greater depth. This latter structure is more favorable as it is better for reducing methane emissions from P. australis soil plant systems.     

Chromate reduction by resting cells of Achromobacter sp. Ch-1 under aerobic conditions

Chromate reduction was carried out by resting cells of Achromobacter sp. Ch-1 with lactate as electron donor under aerobic conditions. The reduction activity of the samples supplemented with lactate was two times as those without lactate. The reduction rate was influenced by initial pH and lactate concentration. Under the optimal conditions, pH 9.0 and 4000 mg l⁻¹ lactate supplement, reduction rate was 5.45 mg l⁻¹ min⁻¹. The reduction rate decreased with increasing of Cr(VI) concentrations and increased with cell densities proportionally. The maximum reduction limit of Ch-1 cells was obtained at 2107 mg l⁻¹ of Cr(VI).     

Isolation of hexavalent chromium resistant bacteria from industrial saline effluents and their ability of bioaccumulation

The mixed cultures has been isolated from industrial saline wastewater contaminated with chromium(VI), using enrichment in the presence of 50 mg l⁻¹ chromium(VI) and 4% (w/v) NaCl at pH 8. In this study, the molasses (M) medium was selected a suitable medium for the effective chromium bioaccumulation by the mixed cultures. Eleven pure isolates obtained from mixed cultures and some of them showed high bioaccumulation in the M media containing about 100 mg l⁻¹ chromium(VI) and 4% NaCl. The strain 8 (99.3%) and 10 (99.1%) were able to bioaccumulate more efficient than the mixed culture (98.9%) in this media. But the highest specific Cr uptake was obtained by the mixed cultures followed by strain 8 and 10 with 56.71, 33.14 and 21.7 mg g⁻¹, respectively. Bioaccumulation of chromium(VI) ions by the strain 8 growing in the media with chromium(VI) and NaCl was studied in a batch system as a function of initial chromium(VI) (86.6–547.6 mg l⁻¹) and NaCl (0, 2, 4, 6% w/v) concentrations. During all the experiments, the uptake yield of the strain 8 was highly affected from NaCl concentrations in the medium at high initial chromium(VI) concentrations. But at low chromium(VI) concentration, strain 8 was not affected from NaCl concentrations in the medium. The maximum uptake yield were obtained in the M media with 2% NaCl as 98.8% for 110.0 mg l⁻¹, 98.6% for 217.1 mg l⁻¹, 98.6% for 381.7 mg l⁻¹ and 98.2% for 547.6 mg l⁻¹ initial chromium(VI) concentrations. The strain 8 tolerated a 6% (w/v) NaCl concentration was able to bioaccumulate more than 95% of the applied chromium(VI) at the 97.6–224.4 mg l⁻¹ initial chromium(VI) concentrations. The results presented in this paper was shown that these pure and mixed cultures might be of use for the bioaccumulation of chromium(VI) from saline wastewater.     

Tolerance,accumulation and distribution of zinc and cadmium in hyperaccumulator Potentilla griffithii

In this study, zinc (Zn) and cadmium (Cd) tolerance, accumulation and distribution was conducted in Potentilla griffithii H., which has been identified as a new Zn hyperaccumulator found in China. Plants were grown hydroponically with different levels of Zn²⁺ (20, 40, 80 and 160 mg L^?1) and Cd²⁺ (5, 10, 20 and 40 mg L^?1) for 60 days. All plants grew healthy and attained more biomass than the control, except 40 mg L^?1 Cd treatment. Zn or Cd concentration in plants increased steadily with the increasing addition of Zn or Cd in solution. The maximum metal concentrations in roots, petioles and leaves were 14,060, 19,600 and 11,400 mg kg^?1 Zn dry weight (DW) at 160 mg L^?1 Zn treatment, and 9098, 3077 and 852 mg kg^?1 Cd DW at 40 mg L^?1 Cd treatment, respectively. These results suggest that P. griffithii has a high ability to tolerate and accumulate Cd and Zn, and it can be considered not only as Zn but also as a potential cadmium hyperaccumulator. Light microscope (LM) with histochemical method, scanning electron microscope combined with energy dispersive spectrometry (SEM-EDS) and transmission electron microscope (TEM) were used to determine the distribution of Zn and Cd in P. griffithii at tissue and cellular levels. In roots, SEM-EDS confirmed that the highest Zn concentration was found in xylem parenchyma cells and epidermal cells, while for Cd, a gradient was observed with the highest Cd concentration in rhizodermal and cortex cells, followed by central cylinder. LM results showed that Zn and Cd distributed mainly along the walls of epidermis, cortex, endodermis and some xylem parenchyma. In leaves, Zn and Cd shared the similar distribution pattern, and both were mostly accumulated in epidermis and bundle sheath. However, in leaves of 40 mg L^?1 Cd treatment, which caused the phytotoxicity, Cd was also found in the mesophyll cells. The major storage site for Zn and Cd in leaves of P. griffithii was vacuoles, to a lesser extent cell wall or cytosol. The present study demonstrates that the predominant sequestration of Zn and Cd in cell walls of roots and in vacuoles of epidermis and bundle sheath of leaves may play a major role in strong tolerance and hyperaccumulation of Zn and Cd in P. griffithii.     

Assessment of Lemna gibba L. (duckweed) as a potential ecological indicator for contaminated aquatic ecosystem by boron mine effluent

Duckweeds, as a group, are important early warning indicators for the assessment of contaminated ecosystems due to their propensity to accumulate pollutants. In the present study, we investigated the potential use of Lemna gibba L. (Lemnaceae) as an ecological indicator for boron (B) mine effluent containing B concentration above 10 mg l⁻¹. For this purpose, L. gibba fronds were grown for 7 days in simulated water contaminated with B mine effluent. The important note is that this study was carried out in Kırka (Eskişehir, Turkey) B reserve area, which is the largest borax reserve in all over the world, under natural climatic conditions in the field. The results demonstrated that accumulations of B by L. gibba gradually increased based on the initial B concentrations (10, 25, 50, 100, and 150 mg l⁻¹) of the mine effluent. B concentration in the dry weight of the plant reached 639 mg kg⁻¹ when the minimum initial dosage (10 mg l⁻¹) was applied and 2711 mg kg⁻¹ when the maximum initial dosage (150 mg l⁻¹) was applied during the study. However, significant reductions in their relative growth rates occurred in 50, 100 and 150 mg l⁻¹ initial B concentrations. Results suggest that 25 mg l⁻¹ B concentration in water seemed to be a sensitive endpoint for L. gibba that could be used as a critical bioindicator level of B contaminated water. Following our data, we also constructed a simple growth model under the climatic conditions in this region of Turkey, but in instructive as a worldwide model. L. gibba is, therefore, suggested to be able to use as both an indicator and a phytoremediation tool because of its high accumulation capacity for B contaminated water.     

Biodegradation of Tapis blended crude oil in marine sediment by a consortium of symbiotic bacteria

Biodegradation rate and the high molecular weight hydrocarbons are among the important concerns for bioremediation of crude oil. Inoculation of a non-oil-degrading bacterium as supplementary bacteria increased oil biodegradation from 57.1% to 63.0% after 10 days of incubation. Both the oil-degrading bacteria and the non-oil-degrading bacteria were isolated from Malaysian marine environment. Based on the 16S rDNA sequences, the oil-degrading bacteria was identified as Pseudomonas pseudoalcaligenes (99% similarity) while the non-oil-degrading bacterium was Erythrobacter citreus (99% similarity). E. citreus does not grow on crude oil enriched medium under present experimental condition but it withstands 5000 mg kg^?1 Tapis blended crude oil in sediment. Under optimal condition, the oil-degrading bacterium; P. pseudoalcaligenes, alone utilized 583.3 ± 3.8 mg kg^?1 (57.1%) at the rate of 3.97 × 10^?10 mg kg^?1 cell^?1 day^?1 Tapis blended crude oil from 1000 mg kg^?1 oil-contaminated sediment. Inoculation of E. citreus as the supplementary bacteria to P. pseudoalcaligenes enhanced biodegradation. The bacterial consortium degraded 675.8 ± 18.5 mg kg^?1 (63.0%) Tapis blended crude oil from the 1000 mg kg^?1 oil-contaminated sediment. Biodegradation rate of the bacterial consortium increased significantly to 4.59 × 10^?10 mg kg^?1 cell^?1 day^?1 (p = 0.02). Improvement of the oil degradation by the bacterial consortium was due to the synergetic reaction among the bacterial inoculants. There are two implications: (1) E. citreus may have a role in removing self-growth-inhibiting compounds of P. pseudoalcaligens. (2) P. pseudoalcaligenes degraded Tapis blended crude oil while E. citreus competes for the partially degraded hydrocarbons by P. pseudoalcaligenes. P. pseudoalcaligenes forced to breakdown more hydrocarbons to sustain its metabolic requirement. The bacterial consortium degraded 78.7% of (C₁₂–C₃₄) total aliphatic hydrocarbons (TAHs) and 74.1% of the 16 USEPA prioritized polycyclic aromatic hydrocarbons.     

Evaluation of distant carbon sources in biosurfactant production by a gamma ray-induced Pseudomonas putida mutant

Pseudomonas putida 33 wild strain, subjected to gamma ray mutagenesis and designated as P. putida 300-B mutant was used as microbial rhamnolipid-producer by using distant carbon sources (viz. hydrocarbons, waste frying oils ‘WFOs’, vegetable oil refinery wastes and molasses) in the minimal media under shake flask conditions. The behavior of glucose as co-substrate and growth initiator was examined. The 300-B mutant strain showed its ability to grow on all the substrates tested and produced rhamnolipid surfactants to different extents however; soybean and corn WFOs were observed to be preferred carbon sources followed by kerosene and paraffin oils, respectively. The best cell biomass (3.5 g l⁻¹) and rhamnolipids yield (4.1 g l⁻¹) were obtained with soybean WFO as carbon source and glucose as growth initiator under fed-batch cultivation showing an optimum specific growth rate (μ) of 0.272 h⁻¹, specific product yield (q_p) of 0.318 g g⁻¹ h and volumetric productivity (P_V) of 0.024 g l⁻¹ h. The critical micelle concentration of its culture supernatant was observed to be 91 mg rhamnolipids l⁻¹ and surface tension as 31.2 mN m⁻¹.     

Chemical compositions and characteristics of organic compounds in propolis from Yemen

Propolis is a gummy material made by honeybees for protecting their hives from bacteria and fungi. The main objective of this study is to determine the chemical compositions and concentrations of organic compounds in the extractable organic matter (EOM) of propolis samples collected from four different regions in Yemen. The propolis samples were extracted with a mixture of dichloromethane and methanol and analyzed by gas chromatography–mass spectrometry (GC–MS). The results showed that the total extract yields ranged from 34% to 67% (mean = 55.5 ± 12.4%). The major compounds were triterpenoids (254 ± 188 mg g⁻¹, mainly α-, β-amyryl and dammaradienyl acetates), n-alkenes (145 ± 89 mg g⁻¹), n-alkanes (65 ± 29 mg g⁻¹), n-alkanoic acids (40 ± 26 mg g⁻¹), long chain wax esters (38 ± 25 mg g⁻¹), n-alkanols (8 ± 3 mg g⁻¹) and methyl n-alkanoates (6 ± 4 mg g⁻¹). The variation in the propolis chemical compositions is apparently related to the different plant sources. The compounds of these propolis samples indicate that they are potential sources of natural bio-active compounds for biological and pharmacological applications.     

Arsenic reduced scale-insect infestation on arsenic hyperaccumulator Pteris vittata L.

Arsenic hyperaccumulation by Pteris vittata L. (Chinese brake fern) may serve as a defense mechanism against herbivore attack. This study examined the effects of arsenic exposure (0, 5, 15 and 30 mg kg^?1) on scale insect (Saissetia neglecta) infestation of P. vittata. Scale insects were counted as a percentage fallen from the plant to the total number of insects after 1 week of As-treatment. The arsenic concentrations in the fronds ranged from 5.40 to 812 mg kg^?1. Greater arsenic concentrations resulted in higher percentage of fallen-scale insects (17.2–55.0%). Lower arsenic concentrations (≤5 mg kg^?1) showed significantly lower effect on the population compared to 15–30 mg kg^?1 (p < 0.05). Arsenic content in the fallen-scale insects was as high as 194 mg kg^?1, which indicated that arsenic has been ingested by the scale insects via plant sap. This study is consistent with the hypothesis that arsenic may help P. vittata defend against herbivore's attack.     

Bioavailability and extraction of heavy metals from contaminated soil by Atriplex halimus

Pot experiments were performed to evaluate the phytoremediation capacity of plants of Atriplex halimus grown in contaminated mine soils and to investigate the effects of organic amendments on the metal bioavailability and uptake of these metals by plants. Soil samples collected from abandoned mine sites north of Madrid (Spain) were mixed with 0, 30 and 60 Mg ha⁻¹ of two organic amendments, with different pH and nutrients content: pine-bark compost and horse- and sheep-manure compost. The increasing soil organic matter content and pH by the application of manure amendment reduced metal bioavailability in soil stabilising them. The proportion of Cu in the most bioavailable fractions (sum of the water-soluble, exchangeable, acid-soluble and Fe–Mn oxides fractions) decreased with the addition of 60 Mg ha⁻¹ of manure from 62% to 52% in one of the soils studied and from 50% to 30% in the other. This amendment also reduced Zn proportion in water-soluble and exchangeable fractions from 17% to 13% in one of the soils. Manure decreased metal concentrations in shoots of A. halimus, from 97 to 35 mg kg⁻¹ of Cu, from 211 to 98 mg kg⁻¹ of Zn and from 1.4 to 0.6 mg kg⁻¹ of Cd. In these treatments there was a higher plant growth due to the lower metal toxicity and the improvement of nutrients content in soil. This higher growth resulted in a higher total metal accumulation in plant biomass and therefore in a greater amount of metals removed from soil, so manure could be useful for phytoextraction purposes. This amendment increased metal accumulation in shoots from 37 to 138 mg pot⁻¹ of Cu, from 299 to 445 mg pot⁻¹ of Zn and from 1.8 to 3.7 mg pot⁻¹ of Cd. Pine bark amendment did not significantly alter metal availability and its uptake by plants. Plants of A. halimus managed to reduce total Zn concentration in one of the soils from 146 to 130 mg kg⁻¹, but its phytoextraction capacity was insufficient to remediate contaminated soils in the short-to-medium term. However, A. halimus could be, in combination with manure amendment, appropriate for the phytostabilization of metals in mine soils.