Microbial solubilization of rock phosphate (RP) considered being an alternative to chemical phosphorous (P) fertilizer, causing high costs and environmental pollution. This work aimed to isolate efficient phosphate solubilizing strains from the estuary region of the Mahanadi river to check their RP solubilizing efficiency, and the mechanisms were discussed. Two strains of bacteria (Bacillus thuringenesis P₀B₁₁ and Lysinobaccillus fusiformis P₀B₂₈) and a fungus (Aspergillus aculeatus P₀F₃) were the most effective strain solubilizing RP. This is the first report of RP solubilization by L. fusiformis P₀B₂₈ and the first report of in vitro stearic acid production during RP solubilization. In particular, the potent strain A. aculeatus P₀F₃ produced the highest soluble P (345.6 mg/l) on 5th day. The soluble P concentration showed a significant negative correlation (r = − 0.88, p ≤ 0.01) with the pH, while it is positively correlated with the growth of B. thuringenesis P₀B₁₁ (r = 0.87, p ≤ 0.01), L. fusiformis P₀B₂₈ (r = 0.55, p ≤ 0.01) and A. aculeatus P₀F₃ (r = 0.96, p ≤ 0.01), respectively. The P release process from rock phosphate fit the first-order kinetics model well (R² = 0.8046–0.8401). Organic acids produced by the isolates found to be the major mechanism for RP solubilization by supplying H⁺ ions and organic anions. High P concentration was related to the high corroded structure formation on the RP surface, reduction in all mineral peak intensities and a large decrease in the intensity of vibrational bands of calcite and fluorapatite confirmed by SEM, XRD, and FTIR, respectively.

Graphic abstract

中文翻译：

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从印度奥里萨邦马哈纳迪河口分离出的微生物对岩石磷酸盐的增溶特征和机理

磷酸盐岩（RP）的微生物增溶作用被认为是化学磷（P）肥料的替代品，导致高成本和环境污染。这项工作旨在从马哈纳迪河河口地区分离有效的磷酸盐增溶菌株，以检查它们的RP增溶效率，并讨论了其机理。最能解决RP的菌株是两种菌株（苏云金芽孢杆菌P ₀ B ₁₁和fusformus梭状芽孢杆菌P ₀ B ₂₈）和真菌（aculgus aculeatus P ₀ F ₃）。这是首个通过梭状芽孢杆菌P ₀ B溶解RP的报告。₂₈和RP增溶过程中体外生产硬脂酸的第一份报告。特别地，强力菌株A. aculeatus P ₀ F ₃在第5天产生最高的可溶性P（345.6 mg / l）。可溶性磷浓度呈显著负相关（ [R  = - 0.88， p  ≤0.01），pH值，而它是积极与生长相关B. thuringenesis P ₀乙₁₁（ [R  = 0.87， p  ≤0.01），大号。羊栖菜P ₀乙₂₈（ [R  = 0.55， p  ≤0.01），棘孢曲霉P ₀˚F ₃（[R  = 0.96，p  ≤0.01），分别。磷矿中磷的释放过程很好地拟合了一级动力学模型（R ²  = 0.8046–0.8401）。发现分离物产生的有机酸是通过供应H ⁺离子和有机阴离子来溶解RP的主要机理。高P浓度与RP表面上高腐蚀结构的形成，所有矿物峰强度的降低以及方解石和氟磷灰石的振动谱带强度的大幅降低有关，分别由SEM，XRD和FTIR确认。

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