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Pb immobilization by phosphate-solubilizing fungi and fluorapatite under different Mn2+ concentrations

Summary

Researchers studied how two types of beneficial fungi (Aspergillus niger and Penicillium chrysogenum) can remove dangerous lead contamination from environments. By adding the mineral fluorapatite and controlling the level of manganese in the growth medium, they found that Aspergillus niger was much more effective at capturing and permanently locking up lead particles, preventing them from leaching back into the environment. The optimal amount of manganese (7.5 mg/L) significantly boosted the fungi’s production of organic acids that capture lead, making this an environmentally friendly solution for cleaning polluted sites.

Background

Lead (Pb) is a persistent environmental contaminant causing high toxicity to organisms. Phosphate-solubilizing fungi (PSF) can produce organic acids to immobilize Pb cations through chelation and mineral formation. Metal cations like Mn2+ influence organic acid secretion by PSF, yet their role in Pb remediation remains insufficiently studied.

Objective

This study investigated the effect of different Mn2+ concentrations (0-30 mg/L) on Pb removal efficiency by two PSF strains: Aspergillus niger and Penicillium chrysogenum, combined with fluorapatite (FAp). The capacity of phosphorus release from FAp and stability of immobilized Pb minerals were also evaluated.

Results

A. niger achieved >99% Pb removal ratio across all Mn2+ concentrations, significantly higher than P. chrysogenum (<90%). Optimal Mn2+ concentration (7.5 mg/L) maximally increased oxalic acid secretion by A. niger (1310.16 mg/L) and PDH enzyme activity (31.53 nmol/min/g), promoting lead oxalate and pyromorphite formation with only 2.25% Pb re-release. High Mn2+ concentrations (15-30 mg/L) inhibited organic acid secretion and Pb immobilization stability.

Conclusion

A. niger is more effective than P. chrysogenum in Pb remediation through superior oxalic acid secretion and mineral formation. An optimal Mn2+ concentration (7.5 mg/L) significantly enhances Pb removal capacity by promoting organic acid secretion and phosphate solubilization, demonstrating that controlling Mn2+ levels is critical for improving PSF-based Pb bioremediation strategies.
  • Published in:Frontiers in Microbiology,
  • Study Type:Experimental Laboratory Study,
  • Source: PMID: 41234738, DOI: 10.3389/fmicb.2025.1696000
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