Removal of High Concentrations Decachlorobiphenyl of Earthworm Eisenia fetida and its Symbiotic Bacteria in a Vermicomposting System

Abstract

The persistent organic pollutants decachlorobiphenyl (DCB) are a group of synthetic substances of high risk to human and environmental health. This study was aimed to evaluate the potential removal of DCB by earthworm Eisenia fetida and its symbiotic bacteria in a vermicomposting system for a period of 72 days using a complete randomized design. The results showed that the vermicomposting system was able to significantly remove high concentrations decachlorobiphenyl (DCB) from the polluted substrate. The addition of a concentration of 1000 mg L−1 during vermicomposting were a removal of 230.28 mg L−1 DCB and the results obtained from adding a concentration of 1500 mg L−1 DCB were 424.11 mg L−1. The earthworms bioaccumulated less than 5 mg L−1 of DCB without an apparent toxic effect. The earthworm weight decreased during vermicomposting and DCB concentration compared to the control (non-polluting); however, earthworms survived until the end of experiment. Phylogenetic analysis of 16S rDNA gene sequences of Eisenia fetida gut strains grown in the presence of 1500 mg L−1 DCB were identified as Bacillus, Paenibacillus, Pseudomonas, Solibacillus, and Staphyloccocus at zero time (0-days). At 7 days of culture, the genera, Acinetobacter, Bacillus, Enterobacter, Klebsiella, and Staphylococcus were identified, and at 72 days, the symbiotic bacteria isolated were classified into the genera, Bacillus, Enterobacter, Klebsiella, and Staphylococcus. The strains Pseudomonas extremaustralis ADA-5 and Staphylococcus sciuri ADA-12 showed higher potential of removal from the DCB (219.7 and 162.74 mg L−1, respectively) at an initial concentration of 1500 mg L−1. Both vermicomposting system and degrading bacteria from Eisenia fetida worms are useful to remove high concentrations of decachlorobiphenyl from contaminated soils. Show more