Isolation and characterisation of a rock solubilising fungus for application in mine-spoil reclamation

- Strain Gongronella sp. NF-15 was isolated as an effective strain for environmental remediation of rocky mining areas.
- The effects of strain NF-15 on rock-weathering and elements release were proved.
- The rock-weathering mechanisms of NF-15 were explored and confirmed by using Structural Equation Model.
- Strain NF-15 was suggested to be applied to solve the problems of thin soil layer and mineral deficiency.

The soil and water loss in rock mining areas is an extremely serious problem, while microbes play significant roles in soil remediation of those areas. In this study, a fungal strain Gongronella sp. NF-15 was isolated from the abandoned dolostone mines, and its mechanism of promoting dolostone dissolution was explored by analyzing the changes of pH value, Ca2+ concentration, Mg2+ concentration, organic acid concentration, micromorphology of rock surface, and rock particle diameter under controlled experimental conditions. After incubation of strain NF-15 with dolostone, the pH value continuously decreased significantly within 15 d, while the concentrations of Ca2+ and Mg2+ rose rapidly (1.8-2.7 times higher than that of control group). High performance liquid chromatography (HPLC) analysis showed that organic acids (succinic acid, citric acid, oxalic acid, malic acid, and lactic acid) were secreted by the strain NF-15 in the process of dolostone dissolution, and succinic acid was found more effective than other organic acids in lowering the pH and accelerating dissolution of rocks by Pearson correlation and Structural Equation Model (SEM) path analysis. In addition, the ultrastructure observation of the rock exhibited the significant erosion by fungal hyphae. Thus, strain NF-15 was suggested to combine with environmental remediation technologies to solve the problems of thin soil layer and mineral deficiency in destroyed dolostone mines. These results not only enrich the available microbial resources but also provide a new strategy for rehabilitating abandoned land in rock mining areas.

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