Kinetics and Novel Degradation Pathway of Permethrin in Acinetobacter baumannii ZH-14

Abstract

Persistent use of permethrin has resulted in its ubiquitous presence as a contaminant in surface streams and soils, yet little is known about the kinetics and metabolic behaviors of this pesticide. In this study, a novel bacterial strain Acinetobacter baumannii ZH-14 utilizing permethrin via partial hydrolysis pathways was isolated from sewage sludge. Response surface methodology based on Box-Behnken design of cultural conditions was used for optimization resulting in 100% degradation of permethrin (50 mg·L−1) within 72 h. Strain ZH-14 degraded permethrin up to a concentration of 800 mg·L−1. Biodegradation kinetics analysis indicated that permethrin degradation by this strain was concentration dependent, with a maximum specific degradation rate, half-saturation constant, and inhibition constant of 0.0454 h−1, 4.7912 mg·L−1, and 367.2165 mg·L−1, respectively. High-performance liquid chromatography and gas chromatography-mass spectrometry identified 3-phenoxybenzenemethanol and 3-phenoxybenzaldehyde as the major intermediate metabolites of the permethrin degradation pathway. Bioaugmentation of permethrin-contaminated soils with strain ZH-14 significantly enhanced degradation, and over 85% of permethrin was degraded within 9 days with the degradation process following the first-order kinetic model. In addition to degradation of permethrin, strain ZH-14 was capable of degrading a large range of synthetic pyrethroids such as deltamethrin, bifenthrin, fenpropathrin, cyhalothrin, and beta-cypermethrin which are also widely used pesticides with environmental contamination problems, suggesting the promising potentials of A. baumannii ZH-14 in bioremediation of pyrethroid-contaminated terrestrial and aquatic environments.

New Insights into the Microbial Degradation of D-Cyphenothrin in Contaminated Water/Soil Environments

“…In the controls with indigenous microbiota, 52.5% of D-cyphenothrin was removed, which is slightly higher than sterilized control (48.2%) and t 1/2 values were noted as 46.2 and 55.5 d, respectively, indicating that indigenous microbiota play a role in the bioaugmentation of pyrethroid-contaminated sites. Similar results were observed by Zhan et al [35]. Nonsterile soil contains natural microbial communities, which led to a higher degradation rate.…”

“…At the end of experiment, all these metabolites faded away without any non-cleavable metabolites. In the non-inoculated controls with the same quantity of D-cyphenothrin, only D-cyphenothrin was detected after 7 d. Among these compounds, α-hydroxy-3-phenoxy-benzeneacetonitrile and 3phenoxybenzaldehyde have been frequently detected in SPs biodegradation [18,35]. These intermediates were transient with very low concentrations and easily transformed into smaller molecular compounds through oxidation and hydrolysis.…”

“…After two days of incubation at 30 • C and 200 rpm, morphological characteristic of strain HLJ-10 (size, color, surface, edge, and texture) were studied under light microscope (Olympus, Tokyo, Japan) and scanning electron microscope (XL-30 ESEM, Philips Optoelectronics Co., Ltd., Holland) [34]. Physio-biochemical assays were conducted with reference to previous literature [35]. The 16S rRNA gene was PCR-amplified with universal set of primer pairs (forward primer: 5 -TGACGAGTGGCGGACGGGTG-3 and reverse primer: 5 -CCATGGTGTGACGGGCGGTGTG-3 ) purchased from Genewiz, NJ, USA.…”

“…This particular strain was found highly effective in degrading D-cyphenothrin up to the concentration as high as 800 mg·L −1 , indicating that strain HLJ-10 may be suitable for the bioremediation of various contaminated environments. Among these compounds, α-hydroxy-3-phenoxy-benzeneacetonitrile and 3-phenoxybenzaldehyde have been frequently detected in SPs biodegradation [18,35]. These intermediates were transient with very low concentrations and easily transformed into smaller molecular compounds through oxidation and hydrolysis.…”

Current Approaches to and Future Perspectives on Methomyl Degradation in Contaminated Soil/Water Environments

“…Compared with physicochemical methods, microbial degradation is considered to be a cost-effective and ecofriendly approach to the removal of pesticide residues [31][32][33]. Biodegrading micro-organisms, including bacteria, fungi, actinomycetes, and algae, can be obtained by enrichment cultures, genetic modification, or gene cloning [70][71][72][73]. Researchers have developed an enrichment culture technique to isolate methomyl-degrading micro-organisms from sewage treatment systems, irrigation areas, and volunteers' stool samples [28][29][30]74].…”