Effects of phosphate-solubilizing fungus Aspergillus flavus AF-LRH1 on promoting phosphorus solubilization, wheat growth and soil heavy metal remediation.

Increasing nutrient supply level and eliminating pollution risk are essential to promote farmland soil use. In the soil-plant nutrition cycle, phosphorus is a limiting nutrient, toxic metals such as Cd and Pb are stress threats. Utilizing microorganisms as a bio-amendment could be a viable approach to enhance the cycling of soil phosphorus nutrients and immobilize Cd and Pb in the soil. This study involved the isolation of Aspergillus flavus AF-LRH1, a phosphate solubilizing fungal strain from soil. The strain exhibited the capacity to solubilize calcium phosphate, attaining a phosphorus concentration of 220.73 mg L⁻¹ in the medium. High performance liquid chromatography analysis showed that AF-LRH1 produced a combination of organic acids (tartaric acid 260.7 mg L⁻¹, fumaric acid 0.8 mg L⁻¹, citric acid 911.9 mg L⁻¹) to dissolve Ca 3 (PO 4) 2 by providing H⁺ ions. AF-LRH1 also utilizes NH 4 ⁺ for the biosynthesis of amino acids and releases protons, which facilitate the dissolution of insoluble Ca 3 (PO 4) 2 and calcium phytate. Through these processes, calcium phosphate is partly converted into hydroxyapatite because of biological solubilization. AF-LRH1 strain showed the capability to recover phosphorus from various types of sludge-based solid residue by increasing the solubility of insoluble phosphate compounds for plant nutrient supply. In addition, the combining addition of AF-LRH1 strain and phosphate-containing amendments (calcium phosphate, sludge ash and biochar) benefited the decontamination of Pb and Cd contaminated soil. This finding confirmed the AF-LRH1 could be a promising environmental-friendly biofertilizer suitable for agricultural applications and bioremediation of heavy metal contaminated soil. [Display omitted] • Aspergillus flavus AF-LRH1 could solubilize inorganic and organic phosphorus. • A possible phosphate solubilization pathway of AF-LRH1 strain was proposed. • Aspergillus flavus AF-LRH1 strain recovered phosphorus from sludge ash and biochar. • Aspergillus flavus AF-LRH1 had the potential to be used as alternate P biofertilizers. • Addition of phosphate solid waste and AF-LRH1 strain favors soil Pb and Pb fixation. [ABSTRACT FROM AUTHOR]