Degradation of DDT by a Novel Bacterium, Arthrobacter globiformis DC-1: Efficacy, Mechanism and Comparative Advantage

Abstract

A novel bacterium, Arthrobacter globiformis DC-1, capable of degrading DDT as its sole carbon and energy source, was isolated from DDT-contaminated agricultural soil. The bacterium can degrade up to 76.3% of the DDT at a concentration of 10 mg/L in the mineral salt medium (MSM) within 1 day of incubation. The effects of various environmental conditions, such as the concentration of DDT, temperature, pH and additional carbon sources, on its growth and biodegrading capacity of DDT were investigated in the MSM. The A. globiformis DC-1 strain could efficiently grow and degrade DDT at a wide range of concentrations, with the maximum growth and degradation rate at 10 mg/LDDT, followed by inhibitory effects at higher concentrations (20 and 30 mg/LDDT). Mesophilic temperatures (25–30 °C) and a pH of 7–7.5 were the most suitable conditions for the growth and biodegradation. The presence of carbon sources significantly increased the growth of the DC-1 strain; however, degradation was inhibited in the present of glucose, sucrose and fructose, and peptone was determined to be the most appropriate carbon source for A. globiformis DC-1. The optimal DDT degradation (84.2%) was observed at 10 mg/LDDT, peptone as carbon source in pH 7.5 at 30 °C with 1 day of incubation. This strain could also degrade DDE, DDD and DDT simultaneously as the sole carbon and energy source, with degradation rates reaching 70.61%, 64.43% and 60.24% in 10 days, respectively. The biodegradation pathway by A. globiformis DC-1 revealed that DDT was converted to DDD and DDE via dechlorination and dehydrochlorination, respectively; subsequently, both DDD and DDE transformed to DDMU through further dechlorination, and finally, after ring opening, DDMU was mineralized to carbon dioxide. No intermediate metabolites accumulation was observed during the GC/MS analysis, demonstrating that the A. globiformis DC-1 strain can be used for the bioremediation of DDT residues in the environment.

The role and mechanisms of microbes in dichlorodiphenyltrichloroethane (DDT) and its residues bioremediation

“…The strains should have a high potential for DDT degradation, and the selected strain could colonize the DDT-contaminated area within a short period of time [136] . The development of strains has a higher capacity to survive under high DDT concentrations [ 71 , 75 , 137 ]. Furthermore, the strain can efficiently survive under a wide range of harsh and suitable environmental conditions [75] .…”

“…The development of strains has a higher capacity to survive under high DDT concentrations [ 71 , 75 , 137 ]. Furthermore, the strain can efficiently survive under a wide range of harsh and suitable environmental conditions [75] . For DDT pesticide degradation, new microbial species should be investigated that have better and faster degradation capacity in contaminated soil environments [138] .…”

“…The DDT-breakdown process by microorganisms benefits from an increase in temperature within a suitable range [161] . Temperature affects the activity of both intracellular and extracellular enzymes of microbes in DDT degradation mechanisms [75] . Microbial enzymes have a variety of optimal enzymes for DDT degradation [162] .…”

“…Microbial enzymes have a variety of optimal enzymes for DDT degradation [162] . Because enzymes are proteins, they are especially susceptible to high temperatures, which may cause the protein to become denatured or alter its characteristics [75] . It was discovered that Pseudoxanthomonas sp.…”