Bioaccumulation of zinc, lead, copper, and cadmium from contaminated sediments by native plant species and Acrida cinerea in South China.

This research was conducted to search and identify spontaneously growing heavy metal-tolerant plant species that are potentially useful for phytoremediation in contaminated sediment. Five sites were selected for collection of plants growing on polluted shore (river bank) sediment of the Xiang River, China. The concentrations of Zn, Pb, Cu and Cd in plants, sediments, and grasshoppers were determined using flame atomic absorption spectrophotometer (AAS700, Perkin-Elmer, USA). Considering translocation factor and bioaccumulation factor, Rumex crispus (Polygonaceae), Rumex dentatus (Polygonaceae), and Lagopsis supina (Labiatae) could be potentially useful for phytostabilization of metals. R. crispus can be considered potentially useful for phytoextraction of Cd. In light of the biomagnification factors, grasshoppers are deconcentrators for Pb and Cd, microconcentrators for Zn and macroconcentrators for Cu to the plants, respectively. To the best of our knowledge, the present study is the first report on Zn, Pb, Cu and Cd accumulation in R. crispus and L. supina, providing a pioneer contribution to the very small volume of data available on the potential use of native plant species from contaminated sediments in phytostabilization and phytoremediation technologies.

[Effects of physico-chemical parameters on the abundance of the denitrification-associated genes nirK, nirS and nosZ during agricultural waste composting].

The abundance variation of the functional genes (nirK, nirS and nosZ) involved in denitrification was investigated using the real-time polymerase chain reaction (real-time PCR) at different locations (top, center and bottom) of the compost pile during the agricultural waste composting. The changes in pile temperature, pH, moisture content, soluble NH4(+) -N, NO3(-) -N and water soluble carbon (WSC) were measured. The results showed that the abundance of those genes varied among the samples collected in different zones. Redundancy analysis (RDA) was applied to explore the correlations between the abundance of nirK, nirS and nosZ and the composting physic-chemical parameters. The results suggested that water soluble carbon (WSC), pile temperature and nitrate had the most significant impacts on the abundance of the three genes. The t-value biplots for each environmental variable indicated that nirK was positively related with temperature and pH (P < 0.05), nirS was positively related with temperature (P < 0.05), and nosZ was positively related with NH4(+) -N while negatively with WSC.

[Research progress on plate mixed culture of lignocellulolytic microorganisms].

Mixed culture of microorganisms has been widely used for the research of lignocellulose transformation and degradation, but the results of the mixed culture are largely affected by the interactions of different lignocellulolytic microorganisms. At present, the researches on these interactions are mainly based on plate mixed culture assay. For this assay, two types of plate were used, namely, basic medium plate and improved medium plate. The basic medium plate is mainly used for the study of colony morphology, mycelia color, exocellular volatile organic compounds, and exocellular enzyme activity, whereas the improved medium plate is used for comparative study, with the carbon sources replaced by natural lignocelloses. This paper summarized the present research status and advancement about the plate mixed culture of lignocellulolytic microorganisms, and put forward a prospect about the focuses of future research in this field.

[Biodegradation mechanism of DDT and chlorpyrifos using molecular simulation].

In order to explore the microscopic degradation mechanism of organic pesticides degrading enzymes, we used molecular docking method to investigate the binding modes of DDT to laccase and chlorpyrifos to organophosphorus hydrolase, and obtained the corresponding complex structures. According to the principle of minimum scoring, the results showed that the MolDock scores were -103.134 and -111.626, re-rank scores were -72.858 and -80.261, respectively. And we used LPC/CSU server search the interactions between organic pesticides and their degrading enzymes. Our results showed that hydrophobic interaction was the strongest contacts in DDT-laccase complex, and both hydrogen bonds and hydrophobic interactions were the strongest contacts when chlorpyrifos-organophosphorus hydrolase complex. The amino acid residues Tyr224 in laccase and Arg254 in organophosphorus hydrolase were detected to play significant roles in catalytic processes.

Effect of saponins on cell surface properties of Penicillium simplicissimum: performance on adsorption of cadmium(II).

Previous studies about the effect of biosurfactants on cell surface properties mainly focus on cell surface hydrophobicity. In the present study, the effects of plant-derived biosurfactants saponins on cell surface charge and the adsorption of cadmium(II) by Penicillium simplicissimum were studied. The pretreatment of saponins changed the optimal pH from 6 to 5 for Cd(II) adsorption. All the adsorption processes by the intact and saponins-pretreated biomasses followed the Langmuir isotherms better than the Freundlich isotherms. According to the Langmuir isotherms, the maximum adsorption of Cd(II) (qmax) was increased from 51.6 to 74.6 mg/l by the pretreatment of 0.025% saponins. The mechanisms were also analyzed by Fourier transform infrared spectrometer (FTIR), energy dispersive X-ray (EDAX), and scanning electron microscope (SEM) analysis. The results indicated that the pretreatment of saponins changed the cell surface charge of P. simplicissimum and therefore influenced the adsorption of cadmium(II).

[Succession of ammonia-oxidizing bacteria community structure during agricultural waste composting].

The dynamic succession of ammonia-oxidizing bacteria (AOB) community during the agricultural waste composting was investigated using the polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE). The changes of pile temperature, pH, moisture content, soluble NH4(+) -N and NO3(-)-N were measured. DGGE results showed that the Shannon-Weaver index changed from 2.58 to 2.02 during the composting process, which reflected the diversity trends downward overall. Nitrosospira and Nitrosomonas were dominant species. Nitrosomonas eutropha,which was found throughout the whole composting process, was identified as a kind of well-tolerated species. Redundancy analysis (RDA) was applied to explore the correlation between the dynamic succession of AOB community and composting physic-chemical parameters. Compared with the slight change referring to its structure during the earlier phase of thermophilic period (4-9 d), the AOB community experienced a more significant change during the later phase of thermophilic period (9-12 d) as well as the following temperature falling phase (12-25 d). Significant relationships have been found between pile temperature, soluble NH4(+) -N (P < 0.01) and NO3(-)-N (P < 0.05) with the dynamic succession of AOB community, which suggested those three parameters were likely to influence, or be influenced by AOB during the agricultural waste composting.