Characterization of genes for enzymes involved in the phenanthrene degradation in Nocardioides sp. KP7

The nucleotide sequence of the gene cluster, phdEFABGHCD, encoding enzymes responsible for the transformation of phenanthrene to 1-hydroxy-2-naphthoate in Nocardioides sp. strain KP7 was determined. This gene cluster, which may constitute a single operon, resided at 6.1-kb downstream of the phdIJK gene cluster encoding the enzymes for the transformation of 1-hydroxy-2-naphthoate to o-phthalate. In general, the phd products exhibited moderate degrees of homology with isofunctional enzymes found in pathways for the degradation of other aromatic compounds. Remarkably, the phdC gene product had features of the [3Fe-4S] type ferredoxin, which has not been found so far as a component of the ring-hydroxylating dioxygenase. Escherichia coli carrying the genes for phenanthrene dioxygenase, phdABCD, was capable to oxidize phenanthrene.     

Dependence of mechanochemically induced decomposition of mono-chlorobiphenyl on the occurrence of radicals

Mechanochemically induced dechlorination of mono-chlorobiphenyl (BP-Cl) on the surfaces of metal oxides was compared with that on metal hydroxides, using the three metals of Mg, Al, and La as examples. The metal oxides, such as gamma-alumina (gamma-Al2O3), magnesium oxide (MgO) and lanthanum oxide (La2O3) showed an efficient ability to dechlorinate the BP-Cl; however, BP-Cl remained in the ground samples when the hydroxides were used. From the product analysis using gas chromatography/mass spectrometry (GC/MS) and electron spin resonance (ESR) measurements, it was confirmed that the charge transfer from the O2- site on the surface of the oxide additives due to the intense grinding has plays a significant role in the decomposition of the chlorinated compound. Based on the observed dependence of the dechlorination on the radical occurrence, some practical methods were proposed to improve the destruction efficiency of the chlorinated organic compounds.     

Debromination of hexabromobenzene by its co-grinding with CaO

A hexabromobenzene (HBB, C6Br6) powder was subjected to co-grinding with excess CaO powder in air using a planetary ball mill to investigate mechanochemical debromination of the HBB sample. The reaction proceeds smoothly with an increase in both grinding time and molar ratio of CaO addition. The co-grinding enables us to debrominate HBB, forming CaBr2, C and CaCO3 besides excess CaO in the product. CaBr2 in the product tends to absorb moisture from the atmosphere to form CaBr2 x nH2O. The reaction yield is quantitatively evaluated by measuring the amount of water-soluble bromide through water washing and the amount of unreacted HBB through toluene washing. It is found that almost 100% of debromination is achieved by 6 h grinding with the molar ratio kept constant at 2:1. Radicals are detected in the ground products, possibly due to rupture in the covalent bonds of C-C and C-Br in HBB.     

Thermodynamic investigation of the effect of oxygen and hydrogen chloride potential upon generation and decomposition behavior of dioxins

The thermodynamic equilibrium of the C‐H‐O‐Cl system has been calculated to elucidate the generation and decomposition behavior of dioxins, and is discussed from the viewpoint of the oxygen and hydrogen chloride potential. The dioxins behavior is greatly dependent on the oxygen potential, i.e. higher temperature and oxygen potential lead to the complete decomposition of dioxins, while low hydrogen chloride potential under insufficient oxygen condition leads to an increase of multi‐chlorine displacement of dioxins.     

Properties of a Poly(3-hydroxybutyrate) Depolymerase from Penicillium funiculosum

A poly(3-hydroxybutyrate) (PHB) depolymerase was purified from a fungus, Penicillium funiculosum (IFO6345), with phenyl-Toyopearl and its properties were compared with those of other PHB depolymerases. The molecular mass of the purified enzyme was estimated at about 33 kDa by sodium dodecyl sulfate (SDS) polyacrylamide gel electrophoresis. The pH optimum and pI were 6.5 and 6.5, respectively. The purified protein showed affinity to Con A-Sepharose, indicating that it is a glycoprotein. Diisopropylfluorophosphate and dithiothreitol inhibited the depolymerase activity completely. The N-terminal amino acid sequence of the purified enzyme was TALPAFNVNPNSVSVSGLSSGGYMAAQL, which contained a lipase box sequence. This purified enzyme is one of the extracellular PHB depolymerase which belong to serine esterase. The purified enzyme showed relatively strong hydrolytic activity against 3-hydroxybutyrate oligomers compared with its PHB-degrading activity. PHB-binding experiments showed that P. funiculosum depolymerase has the weakest affinity for PHB of all the depolymerases examined.     

Enhancement of association of organic molecules on silica gel by surface water: surface photoreaction of stilbene

Here, we show that association of stilbene molecules is facilitated by water on silica gel because of hydrophobic interaction and photodimerization becomes the main photochemical process. Irradiation of trans-stilbene (t-1) on silica gel gives cis-stilbene (c-1), phenanthrene (2), benzaldehyde (3), and dimers r-ctt-4 and r-tct-4. The yields of the dimers increase and those of 2 and 3 decrease with an increase in the amount of t-1 loaded on silica gel. Atmospheric oxygen is responsible for the formation of 2 and 3. The yields of the dimers also increase with an increase in the water on a silica-gel surface and change drastically at the point where the percentage of water to silica gel is around 25 wt%. All active sites on a silica-gel surface would be covered completely with 25 wt% of water.     

Acute toxicity of chlorophenols to earthworms using a simple paper contact method and comparison with toxicities to fresh water organisms

An acute toxicity test of chlorophenols on earthworms (Eisenia fetida) was performed using a simple paper contact method proposed by OECD testing guideline no. 207, that were applied as an earthworm toxicity test. The median lethal concentration, EC50, had significant correlation with logP(ow) (1-octanol/water partition coefficient) of the chemicals. The toxicity of chlorophenols on E. fetida was compared with toxicities for other species: an algae (Selenostrum capricornutum), a crustacean (Daphnia magna), and a fish (Oryzias latipes). It was found that the toxicity of chlorophenols was almost same for E. fetida and for fresh water organisms. These results suggest the possibility of drawing correlations between the effects of pollutants on living things in different environments, fresh water and soil.     

Levels of PCDDs, PCDFs and Co-PCBs in human milk in Saitama, Japan, and epidemiological research

From 1998 to 2000, the dioxin levels were measured in the milk of 299 mothers who lived in Saitama prefecture, Japan. Factors that influenced the dioxin levels were investigated based on a questionnaire given to the milk donors at that time. It was found that the dioxin levels in the milk of the mothers who smoked were lower than those of non-smokers, and the dioxin levels were generally low in the mothers who were heavy smokers. The average dioxin levels in the milk of mothers who had been breast-fed were higher than those given formula, and there was a significant difference in the dioxin congeners. It was also found that the dioxin levels in milk of the women who regularly consumed fish and shellfish were generally higher. There was a strong correlation between summation operator TEQ and PCB126. The data suggested that PCB126 could be a useful indicator for the simplified analysis of dioxin in human milk.     

Possible particulate nitrite formation and its atmospheric implications inferred from the observations in Seoul,Korea

Simultaneous measurements of gaseous species and fine-mode, particulate inorganic components were performed at the University of Seoul, Seoul in Korea. In the simultaneous measurements, a certain level of nitrous acid (HONO) was observed in the gas-phase, indicating possible heterogeneous HONO production on the surface of the ambient aerosols. On the other hand, high particulate nitrite (NO^2?) concentrations of 1.41(±2.26) μg/m³ were also measured, which sometimes reached 18.54 μg/m³. In contrast, low HONO-to-NO₂ ratios of 0.007(±0.006) were observed in Seoul. This indicates that a significant fraction of HONO is dissolved in atmospheric aerosols. Around the Seoul site, sufficient alkalinity may have been provided to the atmospheric aerosols from the excessive presence of NH₃ in the gas-phase. Due to the alkaline particulate conditions (defined in this study as a particle pH >～3.29), the HONO molecules produced at the surface of the atmospheric aerosols appeared to have been converted into particulate nitrite, thereby preventing their further participation in the atmospheric O₃/NO_y/HO_x photochemical cycles. It was estimated that a minimum average of 65% of HONO was captured by alkaline, anthropogenic, urban particles in the Seoul measurements.     

Measurements of aerosol optical properties in central Tokyo during summertime using cavity ring-down spectroscopy: Comparison with conventional techniques

A highly sensitive cavity ring-down spectrometer (CRDS) was used to monitor the aerosol extinction coefficient at 532 nm. The performance of the spectrometer was evaluated using measurements of nearly monodisperse polystyrene particles with diameters between 150 and 500 nm. By comparing the observed results with those determined using Mie theory, the accuracy of the CRDS instrument was determined to be >97%, while the upper limit for the precision of the instrument was estimated to be 0.6–3.5% (typically 2%), depending on the particle number concentration, which was in the range of 30–2300 particles cm^?3. Simultaneous measurements of the extinction (b_ext), scattering (b_sca) and absorption (b_abs) coefficients of ambient aerosols were performed in central Tokyo from 14 August to 2 September 2007 using the CRDS instrument, two nephelometers and a particle/soot absorption photometer (PSAP), respectively. The value of b_ext measured using the CRDS instrument was compared with the sum of the b_sca and b_abs values measured with a nephelometer and a PSAP, respectively. Good agreement between the b_ext and b_sca + b_abs values was obtained except for data on days when high ozone mixing ratios (>130 ppbv) were observed. During the high-O₃ days, the values for b_sca + b_abs were ～7% larger than the value for b_ext, possibly because the value for b_abs measured by the PSAP was overestimated due to interference from coexisting non-absorbing aerosols such as secondary organic aerosols.