Efficient biosequestration of Cr (VI) by Bacillus spp. SSAU-2: Optimization, mathematical modelling, and plant growth promotion

Abstract

Hexavalent chromium (Cr (VI)) is inherently non-biodegradable, persisting in the soil and water for long periods of time; nevertheless, it can be removed from aqueous solutions through the bioremediation process using microbes. In this study, we explore the potential of Bacillus spp. SSAU-2, a chromate-resistant bacterium isolated from the Ganges River, for the bioremediation of Cr (VI) from aqueous environments. Bacillus spp. SSAU-2 demonstrates high efficiency in Cr (VI) removal, even at relatively high contaminant concentrations (up-to 1000 ppm) and has a functional broad physiological range. The removal of Cr (VI) appeared to be highly dependent on the permeability of the cell. Mathematical modelling suggests that SSAU-2 forms multilayer structures with highly heterogeneous porous surfaces. The removal process of Cr (VI) predominantly follows the pseudo-second-order kinetic model. This indicates that the reaction is relatively fast and results in the formation of multilayer structures with highly heterogeneous pores and a predominant physical sorption mechanism. Going beyond conventional metal removal methods, this research explores the unique capabilities of Bacillus spp. SSAU-2 bacterium in diverse physiological conditions, analogous to industrial effluent conditions offering a multifunctional solution that not only efficiently removes Cr (VI) but also enhances plant growth. This highlights a sustainable solution and promising approach to mitigating this environmental hazard.