Halving Gypsum Dose by Penicillium Oxalicum on Alkaline Neutralization and Microbial Community Reconstruction in Bauxite Residue

Bauxite residue is a high-alkaline solid waste generated during the production of alumina, which greatly hinders plant growth. Here,  we have developed a novel integrated approach to stabilize the alkalinity and reduce the amount of Ca-contained solid wastes by the inoculation of alkali-tolerant and acid-producing microorganisms . Compared with 4% (w/w) gypsum, the integrated application of Penicillium oxalicum maintained pH around 9.0 and reduced the amount of gypsum to 2%. Alkaline mineral transformation and organic components conversion analyzed by XRD, XPS, SEM-EDS and spectroscopic technology in both solid and liquid phases of the residues demonstrated that Penicillium oxalicum could alleviate extreme environmental stresses by the screening of organic acids (e.g., oxalic acid) and then neutralize the pH continuously. The ternary plots obtained by high-throughput sequencing revealed that the excessive ameliorants strengthened the metabolic burden of microorganisms and challenged the process of community assembly. The inoculation of Penicillium oxalicum enriched microbial taxa including Pseudomonas , Alkalibacterium , Penicillium oxalicum and Epicoccum nigrum , which may also drive more significant responses of opportunistic taxa groups across the biomes during the amelioration process. Overall, the results provide an ecofriendly strategy to alkaline regulation and secondary risk control by the integration of functional microorganisms and solid wastes of bauxite residue prior to ecological rehabilitation . This work will enhance the understanding of dealkalization in bauxite residue and demonstrate the application potential of functional microorganisms in ecological reconstruction at disposal areas.