Study on the biodegradation of persistent organic pollutants (POPs)

Abstract

The use of organochlorine pesticides, such as dichlorodiphenyltrichloroethane (DDT) and benzene hexachloride (BHC), have contributed substantially to the increase and stable supply of food production post-World War II. However, they have also become a major source of pollution on a global scale due to their persistence in the environment, high bioconcentration, toxicity, and their long-distance mobility. Although the use and production of these pesticides were banned over 45 years ago, they still present a risk to human health and ecosystems, and pose a threat to food safety. These pesticides were designated as persistent organic pollutants (POPs) by the Stockholm Convention in 2001, which urged the industry to reduce or eliminate them globally. The authors of this study have been involved in the research and development of bioaugmentation soil remediation technology to reduce the risk of environmental and crop contamination originating from POPs. In this paper, these studies are summarized, from basic studies (1, 2, 3) to an applied study (4), as follows: (1) use of the soil-charcoal perfusion method to explore POP-degrading bacteria, (2) bacteriological characteristics, metabolic pathways and dechlorination genes of the hexaclorobenzene (HCB)-mineralizing bacterial strain PD653, (3) characteristics and metabolic pathways of the dieldrin-degrading bacterial strain KSF27, and (4) application of these degrading bacteria for remediation of POPs-contaminated soil.

Keywords: Nocardioides sp. PD653; bioremediation; metabolic pathway; novel dehalogenase genes; persistent organic pollutants (POPs); soil–charcoal perfusion system.

Fig. 1. Proposed pathway for the aerobic degradation of HCB and PCNB employed by the strain PD653. The genes involved at each catabolic step are indicated.

Fig. 2. Proposed pathways of dieldrin degradation employed by strain KSF27.

Fig. 3. Simultaneous degradation of four HCH isomers in the contaminated sub-soil using coconut husk charcoal enriched with a constructed bacterial consortium (strainTSK1 + strain PD653). The mean±S.D. for triplicate samples is shown.