Microbiological study on bioremediation of 2,2′,4,4′-tetrabromodiphenyl ether (BDE-47) contaminated soil by agricultural waste composting

Abstract

This paper studied the degradation of 2,2',4,4'-tetrabromodiphenyl ether (BDE-47) in contaminated soil under composting and natural conditions, respectively. BDE-47 residue in agricultural waste-composting pile was determined during 45-day composting. The microbial communities were determined by polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE), and the relationships between the DGGE results and physico-chemical parameters were evaluated by redundancy analysis (RDA) and heatmap-clustering analysis. The results showed that the degradation rate of BDE-47 was significantly higher in agricultural waste-composting pile compared with control group, which was enhanced up to almost 15 % at the end of composting. There were different environmental factors which affected the distribution of composting bacterial and fungal communities. The bacterial community composition was more significantly affected by the addition of BDE-47 compared with other physico-chemical parameters, and BDE-47 had stronger influences on bacterial community than fungal community during the composting. Meanwhile, the most variation in distribution of fungal community was explained by pile temperature.

Effects of Physico-Chemical Parameters on Actinomycetes Communities during Composting of Agricultural Waste

“…However, no significant relationships with Actinomycetes communities were found in this study. Although several researchers [22,37,38] have reported that pile temperature had a significant impact on microbial activity and biomass during composting, no significant correlation between pile temperature and Actinomycetes communities were found during composting in this study. Maybe the influence of pile temperature on Actinomycetes communities were covered by moisture content because of adding deionized water to compost at regular intervals.…”

“…Rice straw, as the typical agricultural waste, was gathered from the suburb of Changsha, Hunan, China, which was used as a difficult-degradable organic material, after air-drying it was cut into 1-2 cm lengths. As a low total carbon/total nitrogen (C/N) raw material, bran was used to adjust the initial C/N ratio of composting which was the optimal C/N ratio for the microbial activity [22]. The characteristics of the above materials are shown in Table 1.…”

“…To ensure the accuracy of the results, the composting pile was performed in triplicate and the results were presented as the mean of these data. The C/N ratio, ambient temperature, moisture content, pH, WSC and pile temperature were measured according to our previous study [22]. Besides that, the ammonium and nitrate of materials were extracted with a 2M KCl solution (materials:solution, 1:5) and its concentrations were determined using the Continuous Flow Analyzer (A33, SEAL Analytical, Norderstedt, Germany).…”

“…Redundancy analysis (RDA) is a multivariate regression analysis used to explain the variation in a set of response variables by another set of explanatory variables. The method has been widely applied to extract and summarize the relationships between microbial community composition and environmental factors [22]. Regression analysis is a statistical method which is utilized for studying the dependence relationships between dependent variables and independent variables [23].…”

“…As shown in Figure1a, the C/N ratio decreased gradually throughout the whole process from 31.15 to 16.62 due to the fact that the organic matter was degraded gradually by the microorganism. Values of C/N ratio lower than 20 at day 27 were considered the threshold value for composting maturity[22]. During the first 6 days, the ammonification and mineralization process produced plenty of ammonium, so the pH increased from 6.74 to 8.87.…”