In controlled incubation experiments, the fungus recovered nearly 40% of the phosphorus trapped in the waste material within 15 days—four times higher than natural dissolution alone. By harnessing microbial metabolism to selectively mobilize phosphorus (P) while limiting unwanted mineral re-precipitation, the study highlights a sustainable strategy to transform a globally accumulated waste into a valuable agricultural resource.
PG is generated when phosphate rock is treated with sulfuric acid to produce phosphoric acid. The material consists mainly of gypsum (CaSO₄·2H₂O) and contains impurities such as fluorides, heavy metals, and radionuclides. Globally, around 300 million tons of PG are produced annually, and more than half is dumped. Over 3 billion tons have already accumulated in stacks. Although PG is considered waste, it still contains about 1% residual P, largely in insoluble forms. Recovering this P could reduce environmental risks such as nonpoint-source pollution while improving phosphorus-use efficiency in agriculture. Traditional chemical extraction methods are often inefficient and dissolve unwanted impurities. Bioextraction of phosphorus (BEP), using phosphate-solubilizing microorganisms, offers a more environmentally friendly alternative. Aspergillus niger, a well-known phosphate-solubilizing fungus, secretes organic acids such as oxalic acid and citric acid that can dissolve insoluble phosphate minerals.
A study (DOI: 10.48130/ebp-0025-0018) published in Environmental and Biogeochemical Processes on 19 January 2026 by Zhen Li’s team, Nanjing Agricultural University, demonstrates that fungal bioextraction can transform phosphogypsum waste into a recoverable and plant-available phosphorus resource, advancing sustainable nutrient recycling and circular waste management.
The researchers systematically investigated the interaction between Aspergillus niger and PG using controlled incubation experiments with varying PG doses (low, medium, and high), combined with measurements of total organic carbon (TOC), fungal biomass, respiration intensity (CO₂ emission), oxalic acid production (HPLC), pH, acid phosphatase activity, phosphorus bioextraction (BEP) efficiency, ATR-IR functional group analysis, NanoSIMS elemental imaging, SEM-EDS mineral characterization, XRF composition analysis, and geochemical modeling using Geochemist’s Workbench (GWB). Results showed that increasing PG dosage markedly stimulated fungal growth: biomass rose from 0.30 g in the control to 0.85 g in the high-PG treatment, while TOC decreased to 0.36–0.38 g/L in medium and high PG treatments, revealing a significant negative correlation between biomass and TOC. Respiration intensity peaked at 8,937 μg C/kg/h in the high-PG system, indicating enhanced metabolic activity. Although oxalic acid concentration appeared low in PG treatments (8–38 mg/L), this was attributed to rapid precipitation of CaC₂O₄ due to abundant Ca²⁺, confirmed by SEM-EDS imaging. pH increased progressively with PG addition (up to 4.0 in high-PG), and acid phosphatase activity was highest under high PG (0.17 μmol/min/mL). BEP efficiency from PG initially remained around 8–12%, but extended incubation significantly improved extraction to 37.81% after 15 days, compared with ~10% without fungus. ATR-IR spectra confirmed phosphate, sulfate, and oxalate functional group transformations. NanoSIMS imaging demonstrated that dissolved phosphorus and sulfate were absorbed into fungal cells, supporting growth and protein synthesis. GWB simulations revealed that increasing pH favored hydroxylapatite formation, while oxalate precipitation of Ca²⁺ reduced phosphorus re-mineralization. Together, these results demonstrate that A. niger enhances phosphorus mobilization from PG through metabolic activity, organic acid secretion, mineral transformation, and selective nutrient uptake.
This study demonstrates that bioextraction using Aspergillus niger offers a selective and sustainable strategy to recover phosphorus from phosphogypsum while limiting impurity mobilization. By converting industrial waste into plant-available nutrients, the PG–fungus system could serve as an efficient microbial phosphate fertilizer. Beyond improving soil phosphorus use efficiency, this approach supports circular resource management and reduces dependence on finite phosphate rock reserves.
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References
DOI
10.48130/ebp-0025-0018
Original Source URL
https://doi.org/10.48130/ebp-0025-0018
Funding Information
This work was supported by the National Key R&D Program of China (Grant No. 2023YFC3707600), and the Research Fund Program of Guangdong Provincial Key Laboratory of Environmental Pollution Control and Remediation Technology (Grant No. 2023B1212060016).
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