Kinetics and New Mechanism of Azoxystrobin Biodegradation by an Ochrobactrum anthropi Strain SH14.

Yanmei Feng,Wenping Zhang,Pankaj Bhatt,Shimei Pang,Ziqiu Lin,Yaohua Huang,Yuming Zhang,Shaohua Chen

doi:10.3390/microorganisms8050625

Yanmei Feng, Wenping Zhang + Show 6 more

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https://doi.org/10.3390/microorganisms8050625

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Abstract

Azoxystrobin is one of the most popular strobilurin fungicides, widely used in agricultural fields for decades.Extensive use of azoxystrobin poses a major threat to ecosystems. However, little is known about the kinetics and mechanism of azoxystrobin biodegradation. The present study reports a newly isolated bacterial strain, Ochrobactrum anthropi SH14, utilizing azoxystrobin as a sole carbon source, was isolated from contaminated soils. Strain SH14 degraded 86.3% of azoxystrobin (50 μg·mL−1) in a mineral salt medium within five days. Maximum specific degradation rate (qmax), half-saturation constant (Ks), and inhibition constant (Ki) were noted as 0.6122 d−1, 6.8291 μg·mL−1, and 188.4680 μg·mL−1, respectively.Conditions for strain SH14 based azoxystrobin degradation were optimized by response surface methodology. Optimum degradation was determined to be 30.2 °C, pH 7.9, and 1.1 × 107 CFU·mL−1 of inoculum. Strain SH14 degraded azoxystrobin via a novel metabolic pathway with the formation of N-(4,6-dimethoxypyrimidin-2-yl)-acetamide,2-amino-4-(4-chlorophenyl)-3-cyano-5,6-dimethyl-pyridine, and 3-quinolinecarboxylic acid,6,8-difluoro-4-hydroxy-ethyl ester as the main intermediate products, which were further transformed without any persistent accumulative product. This is the first report of azoxystrobin degradation pathway in a microorganism. Strain SH14 also degraded other strobilurin fungicides, including kresoxim-methyl (89.4%), pyraclostrobin (88.5%), trifloxystrobin (78.7%), picoxystrobin (76.6%), and fluoxastrobin (57.2%) by following first-order kinetic model. Bioaugmentation of azoxystrobin-contaminated soils with strain SH14 remarkably enhanced the degradation of azoxystrobin, and its half-life was substantially reduced by 95.7 and 65.6 days in sterile and non-sterile soils, respectively, in comparison with the controls without strain SH14. The study presents O. anthropi SH14 for enhanced biodegradation of azoxystrobin and elaborates on the metabolic pathways to eliminate its residual toxicity from the environment.

Highlights

Strobilurin fungicides represent an outstanding new class of pesticides with higher biological activity and specific modes of action [1,2,3]
Cell numbers of strain SH14 increased to its maximum level degradation efficiency against and other research followed by a gradual decrease afterazoxystrobin
In strobilurin comparisonfungicides.Previous to controls, strain SH14 rapidly demonstrated that the bacterial strains from genus Ochrobactrum are metabolically active microbes, degraded azoxystrobin by utilizing it as a growth substrate during the exponential and logarithmic and they are able to degrade and metabolize various xenobiotics[21,26,27,28].To our knowledge, this is phase (0–2 days)

Summary

Introduction

Strobilurin fungicides represent an outstanding new class of pesticides with higher biological activity and specific modes of action [1,2,3]. Over the last two decades, strobilurin fungicides have been widely used and their applications are steadily increasing [4]. Strobilurin fungicides represent an outstanding new class of pesticides with higher biological Microorganisms. Over the last two decades, strobilurin fungicides have2been widely used and their applications are steadily increasing [4]. Numerous studies have demonstrated that strobilurin fungicides are toxic risk to human health [5,6]. Numerous studies have demonstrated that strobilurin fungicides are toxic to both target and non-target species[5,7,8]. Strobilurin fungicides might cause long-term adverse effects on human health [9,10,11,12]

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