Abstract Description

Soil microorganisms, including bacteria, fungi, and algae, hold significant potential for restoring sites that are unsuitable for life following degradation caused by natural disasters or human activities. Therefore, understanding microbial interactions in soil is essential for developing biotechnology practices that contribute to the rehabilitation of degraded lands in many countries. In South Africa, for example, although coal mining offers benefits in energy production, it is a significant cause of land disturbance and degradation. For this reason, the South African government has recommended that mining companies restore mined land to a state suitable for reuse to reduce their environmental impacts. To tackle this issue, a land rehabilitation technology was developed in South Africa using fungal resources: Aspergillus fischeri ECCN 84 and Penicillium sp. ECCN 243. Besides the land reclamation method, this study aimed to produce biofertilisers employing four microbial biocatalysts—specifically plant growth-promoting bacteria (PGPB)—including Arthrobacter sp. ECCN 6b, Enterobacter sp. ECCN 7b, Proteus sp. ECCN 20b, and Serratia sp. ECCN 24b. These microbial samples were isolated from various South African sites–such as algal-based wastewater treatment plants (high-rate algal oxidation ponds, HRAOP), coalfields, and diesel-contaminated soils (DCS)–have demonstrated their ability to solubilise coal and promote plant growth. The plant growth-promoting bacteria (PGPB) were investigated for their potential in bioremediation strategies of coal mining sites. Laboratory tests for PGPs and bioremediation activity included plate and liquid media screening to evaluate low-rank coal (LRC) degradation, production of plant growth regulators (PGR) and essential plant nutrients (EPN), such as IAA, GA3, siderophores, NH₄⁺, PO₄⁻³ and K⁺. The produced IAA had activated adventitious rooting in mung bean (Vigna radiata L.) hypocotyls. As for PEN, they showed positive effects on root and plant biomass production in Fabaceae species, including mung bean (Vigna radiata L.) and sugar bean (Phaseolus vulgaris L.). These organisms could then provide alternative solutions for mine land rehabilitation, the establishment of sustainable agriculture, and the reduction of dependence on chemical fertilisers.