A hydroquinone biosensor using modified core-shell magnetic nanoparticles supported on carbon paste electrode.

A hydroquinone biosensor was developed and used to determine hydroquinone concentration in compost extracts based on the immobilization of laccase on the surface of modified magnetic core-shell (Fe(3)O(4)-SiO2) nanoparticles. Laccase was covalently immobilized on the magnetic nanoparticles by glutaraldehyde, which was modified with amino groups on its surface. The obtained magnetic bio-nanoparticles were attached to the surface of carbon paste electrode with the aid of a permanent magnet to determine hydroquinone. A good microenvironment for retaining the bioactivity of laccase was provided by the immobilization matrix. The linear range for hydroquinone determination was 1 x 10(-7) to 1.375 x 10(-4)M, with a detection limit of 1.5 x 10(-8)M. The current reached 95% of the steady-state current within about 60s. Hydroquinone concentration in compost extracts was determined by laccase biosensor and HPLC, the results of the two methods were approximately the same.

[Removal of Cd from Soil by Aspergillus fumigatus in a Semi-solid Culture].

A method was proposed to remove Cd from contaminated soils by a semi-solid culture containing Aspergillus fumigatus that have a strong resistance to Cd. The removal efficiencies of Cd in different simulated Cd pollution levels were studied and the changes in Cd adsorption and the enrichment in Aspergillus fumigatus were measured. The results showed that Aspergillus fumigatus could remove some Cd from the soil in the semi-solid culture system. When the concentration of Cd was 10 mg·kg-1, the total removal rate of Cd was up to 31%. Meanwhile, the dry weight of Aspergillus fumigatus and the pH of the system were studied during the culture process. The results showed that the dry weight decreased with the increase in culture time and Cd concentration, the maximum decrease rate of dry weight was 64%. The removal efficiency was the best when the pH was varied from 5.6 to 6.0. The changes in different extraction fractions for Cd showed that the main fractions of Cd removed by Aspergillus fumigatus were the acid-soluble fraction and the reducible fraction and the oxidizable fraction of Cd remained essentially unchanged before and after the culturing. The proposed method would provide valuable information for the remediation of heavy metal-contaminated soil by fungi.

[Effects on Physico-chemical Parameters of Glycoside Hydrolase Family 6 Genes During Composting of Agricultural Waste].

Polymerase chain reaction denaturing gradient gel electrophoresis (PCR-DGGE) was used to study the changes of glycoside hydrolase family 6 (GH6 family) genes during the composting of agricultural waste. In addition, a redundancy analysis (RDA) and Monte Carlo permutation test were applied to determine the relationship between the changes to the GH6 family genes and physico-chemical parameters. According to the relative magnitudes of the influence caused by these different parameters on the changes to GH6 family genes, the eight-ranked physico-chemical parameters were pH > pile temperature > total nitrogen (TN) > total organic matter (TOM) > C/N ratio > moisture content > ambient temperature > water soluble carbon (WSC). The eight physico-chemical parameters, which explained 83.1% of the variation of GH6 family genes, confirmed that these parameters had important effects on the GH6 family genes changes. The pH (P=0.002), pile temperature (P=0.004), and TN (P=0.004) had the most significant impacts on these changes. These three significant factors explained 24.92%, 15.57%, and 15.04% of the variation of GH6 family genes, respectively. There were different dominant species which contain GH6 family genes in different stages of composting. The diversity and abundance of GH6 family genes demonstrated these fluctuation trends. The t-value biplots based on the RDA showed that these three significant factors had either positive or negative correlations with the dynamic changes of GH6 family genes and the microbial species contained within GH6 family genes can be generally be divided into five types. The microbial community changes are reflected by the No. 4 to No. 10 bands and these had a significant positive correlation with pile temperature and a significant negative correlation with pH and TN. The microbial community changes reflected by the No. 20 to No. 23 bands had a significant positive correlation with pH and TN.

A novel biosorbent: characterization of the spent mushroom compost and its application for removal of heavy metals.

The spent mushroom compost of Lentinus edodes was used as a biosorbent for adsorbing cadmium, lead and chromium from solutions under batch conditions for the first time. Titration of the biomass revealed that it contained at least three types of functional groups. The Fourier transform infrared spectrometry showed that the carboxyl, phosphoryl, phenolic groups were the main groups. The simulated values of pKH and molar quantity were 5.00 and 0.44 mmol/g, 7.32 and 1.38 mmol/g, 10.45 and 1.44 mmol/g, respectively. The biosorption ability increased with pH in acid condition. When 10 mg/L biomass dosage was added in, there was no significant increment of metal uptake. The maximum uptake estimated with the Langmiur isotherm model were 833.33 mg/g for Cd(II), 1000.00 mg/g for Pb(II) and 44.44 mg/g for Cr(III), respectively. All the results showed that vast potential sorption capacity was existed in the biomass for adsorbing these three kinds of metals studied.

[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.

[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.

[Research and application of producing laccase by Phanerochaete chrysosporium in solid-state fermentation system].

The potential of banana skin and corn cob as a support-substrate for the production of extracellular laccase by the white-rot fungus Phanerochaete chrysosporium (BKMF-1767) was investigated. The results indicate that laccase showed a maximum activity of 12.68 U/g when the proportion of banana skin and corn cob is 1:2 and the inducer is 0.4 mmol/L CuSO4. In addition, crude laccase enzyme shows degradation activity to pentachlorophenol (PCP) without redox mediator or with the redox mediator (ABTS) at a concentration of 5 mmol/L, and the degradation rates of PCP were 37.8% and 97% respectively after 6 h. The crude laccase was purified by treatment of (NH4)2SO4, and the purified laccase could make the degradation rate of PCP to 81.8% within 6 h.

[Microbial community changes during the degradation of straw using phospholipid fatty acid analysis].

Solid-state fermentation system of rice straw was established with the inoculation of soil microorganism and Phanerochaete chrysosporium. Microbial biomass and community structure were investigated using the phospholipid fatty acid (PLFA) technique, and the changes of lignocellulose's degradation rate were also detected during the process. The experimental results show that lignocellulose degradation rate reaches 44% after fermentation. When the total amount of phospholipid fatty acid is separated into indicator phospholipid fatty acids for different groups of microorganisms, these groups show different patterns during the process. Contents of PLFA in gram-positive bacteria, gram-negative and fungi reach their peak value on the sixth day. Gram-positive bacteria have lower contents. The PLFA content ratio of fungi and bacteria is 0.2 - 0.5, so fungi are the main community decomposing lignocellulose. Principal component analysis of the PLFA data show that 18 carbon unsaturated fatty acids are the major fatty acids at the end of the process, which is consistent with the results of indicator phospholipid fatty acids and lignocellulose's degradation rates, so PLFA technique is able to fairly well detect the changes of microbial biomass and community structure in solid-state fermentation system of rice straw.

[Application of white-rot fungi in composting lead-contaminated waste].

Simulative lead polluted wastes which containing unpolluted soil, household waste, straw, bran and lead nitrate were prepared. Inoculation of white-rot fungi and uninoculation in composting of lead-contaminated waste were studied. Change of chemical factor, biological parameter and biological toxicity analyses with time during the composting process were determined to study effect of heavy metal on composting process and probability of application of white-rot fungi in composting of metal-contaminated waste. The results show the composting of lead-contaminated waste inoculated white-rot fungi could be successfully processed, which lead to the reduction of the bioavailability of Pb in compost and alleviate the potential harm from heavy metal. Under this composting process, for the final compost, pH, water-soluble organic carbon/nitrogen, volatile solid, lignin and coarse fibre remained reached 7.9, 4.01, 36.1%, 22.4g, 30.1g, respectively. In addition, 63.38% of Pb in residual fraction and 0% of Pb in soluble-exchangeable fraction were found in final compost, and the germination index of final compost reached 121%.

[Lignin degradation by Penicillium simplicissimum].

A strain of fungi was isolated from soil, which was identified as Penicillium simplicissimum. This strain was capable of utilizing several lignin model compounds, making aromatic dyes decoloration and degrading natural lignin. All these results proved that Penicillium simplicissimum has ligninolytic ability. Three kinds of enzymes were believed to be the most important catalyzes in the biodegrading process. They are lignin peroxidase (LiP), laccase (Lac) and hemicellulase. And they always work synergistically. After 25 days' incubation, the amount of rice straw lignin decreased 0.23g, and the degrading rate was 14.94%. Different from the degrading mechanism of the white-rot fungi, the lignin degradation by P. simplicissimum mainly happened during the primary metabolism and it was greatly influenced by the pH of media, the concentration of Cu2+ and Mn2+.