Enhancing microbial superoxide generation and conversion to hydroxyl radicals for enhanced bioremediation using iron-binding ligands

• Published in: Journal of environmental sciences (China) 2025-01, Vol.147, p.597-606
• Main Authors: Wang, Yuhan, Ning, Xue, Liang, Jinsong, Wang, Aijie, Qu, Jiuhui
• Format: Article
• Language: English
• Subjects: Arthrobacter - metabolism; Biodegradation, Environmental; Bioremediation; Deferoxamine - metabolism; DTPA; Hydroxyl radical; Hydroxyl Radical - metabolism; Iron - metabolism; Iron-binding ligand; Ligands; Soil Microbiology; Soil Pollutants - metabolism; Superoxide; Superoxides - metabolism
• ISSN: 1001-0742
• DOI: 10.1016/j.jes.2023.11.023

•Iron-binding ligands significantly stimulated superoxide production by Arthrobacter strains and other soil bacteria.•Fe(III)-DTPA effectively promoted the conversion of microbial superoxide into hydroxyl radicals.•A rough molar ratio of 1:1 between Fe(III) and DTPA was optimal for production of hydroxyl radicals.•The incorporation of DTPA into microbial cultures containing Fe(III) facilitated the degradation of oxytetracycline. Harnessing bacteria for superoxide production in bioremediation holds immense promise, yet its practical application is hindered by slow production rates and the relatively weak redox potential of superoxide. This study delves into a cost-effective approach to amplify superoxide production using an Arthrobacter strain, a prevalent soil bacterial genus. Our research reveals that introducing a carbon source along with specific iron-binding ligands, including deferoxamine (DFO), diethylenetriamine pentaacetate (DTPA), citrate, and oxalate, robustly augments microbial superoxide generation. Moreover, our findings suggest that these iron-binding ligands play a pivotal role in converting superoxide into hydroxyl radicals by modulating the electron transfer rate between Fe(III)/Fe(II) and superoxide. Remarkably, among the tested ligands, only DTPA emerges as a potent promoter of this conversion process when complexed with Fe(III). We identify an optimal Fe(III) to DTPA ratio of approximately 1:1 for enhancing hydroxyl radical production within the Arthrobacter culture. This research underscores the efficacy of simultaneously introducing carbon sources and DTPA in facilitating superoxide production and its subsequent conversion to hydroxyl radicals, significantly elevating bioremediation performance. Furthermore, our study reveals that DTPA augments superoxide production in cultures of diverse soils, with various soil microorganisms beyond Arthrobacter identified as contributors to superoxide generation. This emphasizes the universal applicability of DTPA across multiple bacterial genera. In conclusion, our study introduces a promising methodology for enhancing microbial superoxide production and its conversion into hydroxyl radicals. These findings hold substantial implications for the deployment of microbial reactive oxygen species in bioremediation, offering innovative solutions for addressing environmental contamination challenges. [Display omitted]