Microbial degradation of polychlorinated biphenyls and dibenzofuran by Burkholderia xenovorans LB400 isolated from landfill leachate /
PCBs and dioxin are the two most dangerous organic chemicals which are listed in Stockholm convention. They are a group of chemically-related compounds known as persistent organic pollutant (POP). Since 1995, Malaysia has banned the importation of PCBs. However, they still continue to persist in our...
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| Main Author: | |
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| Format: | Thesis |
| Language: | English |
| Published: |
Kuantan, Pahang :
Kulliyyah of Science, International Islamic University Malaysia,
2017
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| Subjects: | |
| Online Access: | Click here to view 1st 24 pages of the thesis. Members can view fulltext at the specified PCs in the library. |
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| Summary: | PCBs and dioxin are the two most dangerous organic chemicals which are listed in Stockholm convention. They are a group of chemically-related compounds known as persistent organic pollutant (POP). Since 1995, Malaysia has banned the importation of PCBs. However, they still continue to persist in our environment as it is highly resistance to heat and chemical degradation. The sources of PCBs and dioxin contamination are mostly from disposal waste material such as landfill and municipal solid waste. One of the alternative ways to reduce PCBs and dioxin contamination is through bioremediation by using microorganism to breakdown pollutants into less or non-toxic compounds. There are many factors involve in successful biodegradation process such as electron acceptors, pH, concentration of substrate, temperature as well as the expression gene level of the microorganism. Thus the main focus of this study is to determine the degradation of PCBs and dibenzofuran (DBF) in landfill leachate by Burkholderia xenovorans LB400. This study also determines the concentration of PCBs and DBF before and after degradation as well as gene expression level during the degradation. There are three parts involve in this study; extraction optimization of PCBs and DBF from landfills leachate, degradation of PCBs and DBF by Burkholderia xenovorans LB400 and bphA gene expression of Burkholderia xenovorans LB400. In the first part, four solvent systems; hexane, dichlorometane, hexane:acetone and hexane:dichlorometane were used to determine the best extraction solvent of PCBs and DBF in landfills leachate. Hexane was identified to be the best solvent extraction for both of the compounds. The optimized solvent was then applied for detection of PCBs and DBF in landfill leachate and in solid phase extraction (SPE) in the second part of the study. Furthermore, the growth parameters of Burkholderia xenovorans LB400 in the study were optimized involving substrate concentration, incubation temperature and pH medium. The best parameters of the Burkholderia xenovorans LB400 growth in M9 minimal media supplemented with 15 ppm of the compounds (PCBs or DBF), incubation temperature of 30˚C and pH 7 of media. The optimized growth parameters were then applied for 10% (v/v) landfill leachate. The degradation study of both compounds (PCBs or DBF) showed significant different between Burkholderia xenovorans LB400 incubated in media supplemented with PCBs in 10% (v/v) landfill leachate compared to all the treatments. This result was supported by gene expression analysis in the last part of the study where bphA gene that encodes for biphenyls dioxygenase was highly expressed in the media supplemented with PCBs in 10% (v/v) landfill leachate thus enhanced the degradation of PCBs via biphenyls degradation pathway. This result indicate LB400 was more likely to degrade PCBs compared to DBF. Furthermore, landfill leachate also play an important role in influencing the rate of PCBs and DBF degradation as well as expression of bphA gene by Burkholderia xenovorans LB400. |
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| Physical Description: | xv, 146 leaves : illustrations ; 30cm. |
| Bibliography: | Includes bibliographical references (leaves 116-137). |