Feasibility Analysis of Bacterial-Treated Coal Gangue for Soil Improvement: Growth-Promoting Effects of Alfalfa

Abstract

The long-term storage of coal gangue (CG) mountains causes serious environmental problems such as water and air pollution. Thus, sustainable reclamation practices are urgently needed to minimize the environmental impacts brought by CG mountains. Pikovskaya medium was employed to screen microorganisms, which were subsequently utilized to promote the solubilization of CG. XRF, SEM, XRD, and HPLC techniques were employed to characterize the CG before and after bacterial treatment. In this study, we have successfully isolated and purified a bacterial strain, identified as Stenotrophomonas bentonitica BII-R7, which possesses the ability to facilitate the solubilization of nutrient elements from CG. Factors including initial inoculation ratio, incubation time, CG particle size, CG concentration, pH, and temperature were examined to investigate their effects on the biosolubilization of CG. Furthermore, the mechanism underlying the CG solubilization was also probed. Our data demonstrated that low-molecular-weight organic acids, such as acetic acid and formic acid, may harbor a crucial role in promoting the solubilization of CG. Lastly, we found that Stenotrophomonas bentonitica BII-R7, in conjugation with CG, can increase the alfalfa seed germination percentage and promote the growth of alfalfa. Together, these data provide evidence that bacterial-treated CG can be utilized for soil improvement and land reclamation.