[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.