Effect of Acid Production by Penicillium oxalicum on Physicochemical Properties of Bauxite Residue

Abstract

Large-scale discharge of bauxite residue, an alkaline, saline and nutrientdeficient waste material produced in the process of alumina production, has created extreme environments that are challenging to restore. Microbial pathways are found to play a critical role in the rehabilitation of these residues. In this study, Penicillium oxalicum, an alkaliresistant acid-producing fungus screened from bauxite residue disposal sites, was used to examine its effectiveness for restoration of bauxite residue. By comparing different biomass pretreatment methods, steam explosion pretreatment biomass was added to the medium to enhance microbial metabolism, through production of organic acids and various enzymes. P. oxalicum mainly secreted oxalic acid, formic acid and acetic acid. Addition of pretreatment biomass and microbes significantly lowered bauxite residue pH, whilst increasing EC and enzyme activity. Furthermore, the metabolic process of this fungus may promote the release of basic ions dominated by Na + and increase soluble cations. This study provides an experimental demonstration of bioremediation in bauxite residue, and enables future large-scale simulation of vegetation establishment on bauxite residue disposal areas.

Neutralization and Improvement of Bauxite Residue by Saline-Alkali Tolerant Bacteria

“…Correlation analysis indicated that the medium pH was significantly negatively correlated with the secretion of total organic acid content ( Table S4 ). These results further verified that acid fermentation was the major mechanism for decreasing the pH of the medium, which is consistent with previous reports [ 20 , 29 ].…”

“…However, most previous studies emphasized the importance of amendments, and the roles of microorganisms in reducing the pH of BR was ignored to a certain extent. With the rapid development of biotechnology, the critical role of microorganisms in decreasing the pH of BR has been recognized [ 20 , 29 ]. Some exploratory studies on reducing the pH of BR by microorganisms have been conducted in recent years, including bacterial, fungal and microbial-rich amendments [ 33 , 35 ].…”

Stable Aggregate Formation and Microbial Diversity Resilience in Soil Formation of Bauxite Residue: Roles of Extracellular Polymeric Substances Secreted by Penicillium oxalicum

“…P. oxalicum was cultivated according to the previously mentioned . The straw was added to a 2% v/v H 2 SO 4 solution at a ratio of 1:5 (w/v) and washed with deionized water more than 3 times.…”

“…P. oxalicum was cultivated according to the previously mentioned. 29 The straw was added to a 2% v/v H 2 SO 4 solution at a ratio of 1:5 (w/v) and washed with deionized water more than 3 times. The treated straw was then mixed with P. oxalicum liquid at a ratio of 1:2 (w/v) to serve as a microbial inoculant (details in Supporting Information 2.1).…”

Intracellular Metabolomics Switching Alters Extracellular Acid Production and Insoluble Phosphate Solubilization Behavior in Penicillium oxalicum

“…This short-chain saturated triglyceride is a major product of amino acid and dicarboxylic acid metabolism (consuming glycerol as an ideal source) and a precursor of carboxylic acid metabolism [36,38]. Microbes can convert propionic acid to propionyl-CoA and utilize it for carboxylic acid (including gluconic, galactaric, and glucuronic acid) production [36,39]. Significantly increased levels of propionic acid were only observed in IP treatment (Figures 4 and 6), suggesting that amino acids were used and converted into gluconic acid in the IP treatment, which was consistent with the lack of a significant increase in the amino acids methionine, serine and tyrosine involved in propionic acid production and the increase in glyceric acid (FC > 2) in IP treatments (Figure 4) [40].…”