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

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.

Dissipation Behavior, Residue, and Risk Assessment of Benziothiazolinone in Apples

“…The degradation dynamics and dissipation curves ( n = 3) of benziothiazolinone in apple in Anhui and Ningxia are presented in Figure 3 . The residue of benziothiazolinone in apple gradually decreased with time, and the dissipation process was of first-order reaction kinetics [ 21 , 22 , 23 ]. The initial concentrations of benziothiazolinone at 0 days (2 h after application) in apple were low both in Anhui and Ningxia, and the degradation half-lives of benziothiazolinone were 33.0 days and 23.9 days with dissipation equations of and , respectively.…”

Characterization of a Novel Quorum-Quenching Bacterial Strain, Burkholderia anthina HN-8, and Its Biocontrol Potential against Black Rot Disease Caused by Xanthomonas campestris pv. campestris

“…The sequences were analyzed by the nucleotide Basic Local Alignment Search Tool (BLASTn), compared to the genes in the GenBank database, and then deposited in GenBank (accession number: MG561937.1). Similar and relevant sequences were downloaded from the National Center for Biotechnology Information (NCBI), and were used for phylogenetic analysis and construction of the phylogenetic tree [ 45 ].…”

Insights into the Toxicity and Degradation Mechanisms of Imidacloprid Via Physicochemical and Microbial Approaches

“…The advantages of biodegradation are (1) its strong selectivity; (2) its safety to people, livestock, crops, and the natural environment; (3) it does not harm natural enemies; and (4) it does not easily produce resistance [106][107][108][109][110]. Microbial degradation is a clean, efficient, and ecologically friendly method for the remediation of organic compounds in soil and water without secondary pollution [11,[111][112][113]. As such, several imidacloprid-degrading strains have been isolated and characterized ( Table 3).…”