Efficient bioimmobilization of cadmium contamination in phosphate mining wastelands by the phosphate solubilizing fungus Penicillium oxalicum ZP6

Abstract

In recent years, Cd contamination in phosphate mining wastelands has become increasingly serious, posing a great threat to ecological stability and human health. In this study, we aimed to investigate the bioremediation effect and mechanisms of phosphate-solubilizing fungi (Penicillium oxalicum ZP6) on Cd contamination in phosphate mining wastelands. A liquid shake-flask experiment showed that strain ZP6 was able to solubilize phosphate rock by reducing the pH, thus effectively removing Cd2+. Moreover, strain ZP6 adsorbed Cd2+ mainly through tight binding. Soil experiments showed that 81.64% Cd2+ removal was achieved after 21 d of inoculation with ZP6. FTIR and XRD analyses revealed that strain ZP6 achieved bioimmobilization of Cd2+ through the formation of Cd-phosphate and Cd-oxalate precipitates. Inoculation with strain ZP6 increased the microbial community diversity of Cd-contaminated soil from a phosphate mining wasteland, increasing the relative abundance of unclassified-d-unclassified and Actinobacteria. The activation of high-abundance genes (ATPF1A, atpD, GGT, cydA, and G6PD) was promoted, thereby enhancing the expression of signaling and metabolism-related functional genes. Our study indicates that strain ZP6 has enormous potential for bioremediation of Cd in phosphate mining wastelands. It also provides an efficient, green and economical biomaterial for remediating Cd contamination in phosphate mining wastelands.