Jiachao Zhang

Effects of physico-chemical parameters on the bacterial and fungal communities during agricultural waste composting.

The goal of this study was to identify and prioritize some of the physico-chemical parameters that contributed to bacterial and fungal community compositions during agricultural waste composting. Relationships between those parameters and microbial community compositions determined by PCR-DGGE were simultaneously evaluated by redundancy analysis (RDA). The results showed that the temporal variation of bacterial community composition was significantly related to water soluble carbon (WSC), ammonium and nitrate (P<0.05), while the most variation in distribution of fungal community composition was statistically explained by pile temperature, WSC, and moisture content (P<0.05). Significant amounts of the variation (54.9% and 56.0% for bacterial and fungal species data, respectively) were explained by those parameters, suggesting that those parameters were the most likely ones to influence, or be influenced by the bacterial and fungal species. Variation partitioning analyses indicated that WSC and pile temperature showed predominant effect on the bacterial and fungal community composition, respectively.

The formation of bio-oil from sludge by deoxy-liquefaction in supercritical ethanol.

A novel deoxy-liquefaction of sludge to liquid fuel (CH(2.07-1.40)O(0.30-0.06)N(0.09-0.05)S(0.02-0.0032)) was studied in supercritical ethanol. The reduction of oxygen atoms combined with hydrogen to produce H(2)O weaken the reduction of oxygen atoms in the form of CO and CO(2), and the latter process is the primary process for the reduction of oxygen during deoxy-liquefaction. The significant increment of oil and residue fractions yield was obtained in excess ethanol as extraction and polymerization process. The addition of Fe-catalyst could promote the catalytic activity of hydrogenation for free radicals, but inhibited the liquefaction conversion. Esters and acids were identified as main compounds as the decomposing, extraction and esterification process. The conversion of free radicals and intermediates to products with heterocyclics and phenol ring was promoted, and the formation of medium-boiling-point compounds without heterocyclics and phenol ring structure was inhibited at higher temperature and higher solvent filling ratio.

Effects of inoculation with Phanerochaete chrysosporium at various time points on enzyme activities during agricultural waste composting.

The effect of inoculation times on the enzyme activities during agricultural waste composting was determined. Four runs were used: without inoculation (Run A), inoculation with Phanerochaete chrysosporium (P. chrysosporium) during the first fermentation phase (Run B), inoculation during the second fermentation phase (Run C) and inoculation during both the first and the second fermentation phase (Run D). The results revealed that the effect of inoculation on carboxy methyl cellulase (CMCase) activities was negative during the first fermentation phase. The inoculation increased the activities of xylanase (almost 3000 U/g) during the first fermentation phase but no obvious difference among Runs A-D was observed during the second fermentation phase. The peak values of manganese peroxidase (MnP) in Runs C and D were three times higher than those of Runs A and B on day 21. The inoculation positively affected the lignin peroxidase (LiP) activities during the first fermentation phase and had a significant negative effect on the laccase (Lac) activities during the second fermentation phase. Therefore, the inoculation during the second fermentation phase was more effective than that during the first fermentation phase.

Relative contributions of archaea and bacteria to microbial ammonia oxidation differ under different conditions during agricultural waste composting.

The aim of this study was to compare the relative contribution of ammonia-oxidizing archaea (AOA) and bacteria (AOB) to nitrification during agricultural waste composting. The AOA and AOB amoA gene abundance and composition were determined by quantitative PCR and denaturing gradient gel electrophoresis (DGGE), respectively. The results showed that the archaeal amoA gene was abundant throughout the composting process, while the bacterial amoA gene abundance decreased to undetectable level during the thermophilic and cooling stages. DGGE showed more diverse archaeal amoA gene composition when the potential ammonia oxidation (PAO) rate reached peak values. A significant positive relationship was observed between the PAO rate and the archaeal amoA gene abundance (R²=0.554; P<0.001), indicating that archaea dominated ammonia oxidation during the thermophilic and cooling stages. Bacteria were also related to ammonia oxidation activity (R²=0.503; P=0.03) especially during the mesophilic and maturation stages.

Response of compost maturity and microbial community composition to pentachlorophenol (PCP)-contaminated soil during composting.

Two composting piles were prepared by adding to a mixture of rice straw, vegetables and bran: (i) raw soil free from pentachlorophenol (PCP) contamination (pile A) and (ii) PCP-contaminated soil (pile B). It was shown by the results that compost maturity characterized by water soluble carbon (WSC), TOC/TN ratio, germination index (GI) and dehydrogenase activity (DA) was significantly affected by PCP exposure, which resulted in an inferior degree of maturity for pile B. DGGE analysis revealed an inhibited effect of PCP on compost microbial abundance. The bacteria community shifts were mainly consistent with composting factors such as temperature, pH, moisture content and substrates. By contrast, the fungal communities were more sensitive to PCP contamination due to the significant correlation between fungal community shifts and PCP removal. Therefore, the different microbial community compositions for properly evaluating the degree of maturity and PCP contamination were suggested.

Compound microsatellites in complete Escherichia coli genomes.

Compound microsatellites consisting of two or more repeats in close proximity have been found in eukaryotic genomes. So far such compound microsatellites have not been investigated in any prokaryotic genomes. We have therefore examined compound microsatellites in 22 complete genomes of Escherichia coli, which is one of the ideal model organisms to analyze the nature and evolution of prokaryotic compound microsatellites. Our results indicated that about 1.75–2.85% of all microsatellites could be accounted as compound microsatellites with very low complexity, and most compound microsatellites were composed of very different motifs. Compound microsatellites were significantly overrepresented in all surveyed genomes. These results were dramatically different from those in eukaryotes. We discussed the possible reasons for the observed divergence.

Feasibility of bioleaching combined with Fenton-like reaction to remove heavy metals from sewage sludge

Feasibility of bioleaching combining with Fenton-like reaction to remove heavy metals from sewage sludge was investigated. After 5-day bioleaching, the sludge pH decreased from 6.95 to 2.50, which satisfied the acidic conditions for Fenton-like reaction. Meanwhile, more than 50% of sludge-borne heavy metals were dissolved except for Pb. The bioleached sludge was further oxidized with Fenton-like reaction, with an optimal H2O2 dosage of 5 g/L, the Cu, Zn, Pb and Cd removal reached up to 75.3%, 72.6%, 34.5% and 65.4%, respectively, and the residual content of heavy metals in treated sludge meets the requirement of Disposal of Sludge from Municipal Wastewater Treatment Plant - Control Standards for Agricultural Use (CJ/T 309-2009) of China for A grade sludge. Bioleaching combined with Fenton-like reaction was the most effective method for heavy metal removal, compared with 15-day bioleaching and inorganic acid leaching with 10% H2SO4, 10% HCl and 10% HNO3.

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).

Removal and recovery of Zn2+ and Pb2+ by imine-functionalized magnetic nanoparticles with tunable selectivity.

This research investigated the adsorption of zinc and lead from binary metal solution with tunable selectivity. A nano adsorbent was prepared by introducing imine groups onto the surface of stability enhanced magnetic nanoparticles and then characterized by TEM and FTIR. Binary metal components adsorption was carried out in different concentration of metal and EDTA solution. Due to the interaction between metals and adsorbent in the presence of EDTA, the selective adsorption of zinc and lead could be achieved with 100% selectivity. To only remove zinc from binary metals, the solution condition was [EDTA]/[M(2+)] = 0.7 with pH of 6, and its saturated adsorption capacity was 1.25 mmol/g. For selective adsorption of lead, an equilibrium adsorption capacity of 0.81 mmol/g was obtained under the condition of [EDTA]/[M(2+)] = 0.7 and pH of 2. The exhausted adsorbent could be regenerated by simple acid or alkali wash, and high purity lead and zinc salt solutions were recovered and concentrated.

Influence of rhamnolipids and Triton X-100 on adsorption of phenol by Penicillium simplicissimum.

The effects of rhamnolipids and Triton X-100 on phenol adsorption by Penicillium simplicissimum were studied. The optimum pH was 7 for phenol adsorption by all the test biomasses. The adsorption of phenol at pH 7 by biomass pre-treated with 0.05% Triton X-100, 0.2% Triton X-100, 0.05% rhamnolipids and 0.005% rhamnolipids was 3.4, 2.7, 2.4, and 1.8-fold, respectively, that of untreated biomass. The pseudo-second-order model and the Freundlich isotherms described the adsorption processes better than the pseudo-first-order model and the Langmuir isotherms, respectively. The pre-treatments by surfactants increased the zeta potential and hydrophobicity of P. simplicissimum. Analysis of the cell surface by Fourier transform infrared spectrometry, energy dispersive X-ray, and environmental scanning electron microscopy indicated that the pre-treatments by surfactants changed the cell surface functional groups, element concentrations and micrographs. The results indicated that surfactants can be potentially used to increase phenol adsorption.