Dichlorodiphenyltrichloroethane (DDT) degradation by Streptomyces sp. isolated from DDT contaminated soil

Abstract

Bioaccumulation, toxicity and long-range transport of persistent organic pollutants (POPs) is a threat to soil and other ecosystems, therefore removal of such pollutants from soil is required. This study thus aimed to isolate and identify bacteria capable of biodegrading a persistent organic pollutant; dichlorodiphenyltrichloroethane (DDT) from a former DDT production unit. The soil was sampled, transported to Japan through standard protocols and bacteria were isolated and assayed for dichlorodiphenyldichloroethane (DDD) and dichlorodiphenyldichloroethylene (DDE) degradation. The concentration of DDTs in a composite soil sample was 0.7 mg kg⁻¹. Twenty-four bacterial strains were isolated from DDT-contaminated soil, and one of them, strain 885, showed degradation of DDT but could not degrade DDE after 14 days of incubation. This strain also showed significant degradation of 15.6 µM DDD (degradation rate 55.9%) after 28 days incubation. Further metabolites of DDT including 2,2-bis(p-chlorophenyl) ethanol (DDOH) and 4,4-dichlorobenzophenone (DBP) were detected from a 14-day incubation culture with DDD as initial substrate. Strain 885 also showed degradation of metabolites of DDT including those of DDOH, and DBP. In conclusion, strain 885 successfully degraded DDT; therefore, it can be used for remediation of DDT-contaminated soil.

Keywords:

• Biodegradation
• dichlorodiphenyltrichloroethane (DDT)
• persistent organic pollutants
• Streptomyces

Acknowledgments

We would like to thank Ali Asim, Daud Shah Kakakheil, Ghani Rehman, and Dr. Abdul Rashid (Pakistan Academy of Sciences) for their support in soil sampling and importation. We thank Catherine Dandie, PhD, from Edanz Group (https://en-author-services.edanzgroup.com/) for editing a draft of this manuscript.

Disclosure statement

The authors declare no conflict of interest.

Additional information

Funding

This work was supported by the Japan Society for the Promotion of Science (JSPS), Ministry of Education, Culture, Sports, Science and Technology, Japan [KAKENHI Grant Number 18H02319]. Ahmad Mahmood was supported by a scholarship from the Rotary Yoneyama Memorial Foundation.