Aspergillus Tubingensis Reduces the pH of the Bauxite Residue (Red Mud) Amended Soils

Abstract

Bauxite residue (red mud), a poor substrate for plant growth because of very high pH, salinity and sodicity, is required to be revegetated. The possibility of using Aspergillus tubingensis (AT1), a phosphate solubilizer in red mud amended soils to reduce the alkalinity of the red mud was studied in the present study. A. tubingensis was tested for its ability to grow at high pH and in different concentrations of aluminium (Al), iron (Fe) and sodium (Na). The results showed that A. tubingensis was able to grow at high pH and reduce the alkalinity of the nutrient medium and also to accumulate different metals in the mycelium. The pH values of the red mud amended soils were also significantly reduced (by 2-3 units) by A. tubingensis, which resulted in maize growth improvement. These results suggest that A. tubingensis plays an important role in reducing the pH of the red mud and also helps in promoting the plant growth in it.

An alkaliphilic and xylanolytic strain of actinomycetes Kocuria sp. RM1 isolated from extremely alkaline bauxite residue sites

“…The pH of the bauxite residue was 11.1; electrical conductivity (EC) 4.9 ls/cm; organic carbon 0.0036 mg/g; available P: 0.0014 mg/g and total nitrogen was below detectable level. Predominantly, iron oxide (47%) and aluminium oxide (*7%) were two major constituents of red mud (Krishna et al 2005).…”

A review of the characterization and revegetation of bauxite residues (Red mud)

“…Further research has shown that sustained nutrients are necessary to support the activation of alkaliphilic microbes. Krishna et al (2005) also found that Aspergillus tubingensis played an important role in reducing bauxite residue pH and helped to promote plant growth. Microbes have beneficial effects to improve the chemical properties of bauxite residue.…”

“…Untreated bauxite residue is a sterile substrate for plant and microbial growth and nutrient availability (Krishna et al 2005). All the physical and chemical properties which limit vegetation establishment on bauxite residue can also limit the growth and colonization of microorganisms.…”

Red mud as an amendment for pollutants in solid and liquid phases

“…The sewage sludge amendment significantly increased dry weight yield and provided sufficient nutrients for plant growth except K. After evaluating the effects on soil physical properties of red mud amended with sewage sludge and gypsum, they found that sewage sludge can significantly reduce soil bulk density (25%), particle density (9%) and increase the total porosity of red mud (8%) as well as hydraulic conductivity(from 1.5 to 23 × 10 − 5 m/s). Krishna et al (2005) selected a basophilic bacteria, Aspergillus tubingensis, for amending red mud for revegetation. This reduces its pH.…”