Siderophore-Producing Bacteria from the Santiago River: A Quantitative Study and Biocomposite Applications

TL;DR

Bacteria from a polluted river produce metal-binding compounds that can be used in biocomposites to remove heavy metals like copper from contaminated water.

Contribution

A novel carbon–bacteria biocomposite using siderophore-producing bacteria was developed for enhanced heavy metal remediation.

Findings

Bacillus thuringiensis immobilized on activated carbon showed 23.9% higher Cu(II) sorption capacity than activated carbon alone.

CBM-treated effluents showed reduced toxicity in Vibrio fischeri assays, indicating safer water after treatment.

Abstract

The Santiago River near the Guadalajara Metropolitan Area is one of the most contaminated water bodies in Mexico, where heavy metals pose a major threat to aquatic ecosystems. Chronic metal pollution has promoted the adaptation of native microbial communities, including the production of metal-chelating metabolites such as siderophores, which represent a valuable resource for remediation-oriented biomaterials. In this study, bacterial strains were isolated from water and sediment samples, then screened for siderophore production using the Chrome Azurol S assay (CAS), complemented by a MATLAB-based image processing approach for semi-quantitative ranking prior to taxonomic identification by MALDI-TOF MS. Based on biosafety considerations and cultivation robustness, Bacillus thuringiensis was selected as a benchmark case, being immobilized onto activated carbon to produce a carbon–bacteria biocomposite (CBM). To evaluate the performance of CBM, Cu(II) was used as a model contaminant due to its industrial relevance, persistence, toxicity, and strong complexation behavior. Batch adsorption experiments showed that the CBM exhibited a 23.9% higher maximum Cu(II) sorption capacity than pristine activated carbon. Acute toxicity assays using Vibrio fischeri further indicated reduced toxicity in CBM-treated effluents, supporting the feasibility of this contained biocomposite for heavy metal remediation.

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