Carbonic anhydrase-mediated phosphogypsum degradation and enhanced CO2 sequestration: a promising sustainable strategy for biological resource utilization of phosphogypsum.

Abstract

Aims: This study continues our previous investigation of the intrinsic degradation of phosphogypsum (PG) by indigenous microorganisms on amending adequate nutrients. We aim to unravel the intricate mechanisms involved in PG biotransformation by a bacterial consortium.

Methods and results: We isolated and characterized seven multi-metal-resistant bacterial strains from a nutrient-amended PG-contaminated microcosm and identified them through 16S rRNA gene sequencing. Primarily aerobic, Gram-positive chemolithotrophs, these strains demonstrated significant heavy metal uptake and PG degradation potential. Further analysis revealed that all strains produced carbonic anhydrase (CA), while six also produced urease, which may facilitate microbial-induced carbonate precipitation. Microstructural and elemental analysis using scanning electron microscopy-energy-dispersive X-ray and X-Ray Diffraction (XRD) confirmed the PG bio-transformation, indicating substantial increases in carbonate concentrations and reductions in sulfate levels.

Conclusions: The consortium, composed of seven urease- and CA-producing bacterial strains, effectively degraded PG, transforming it from an acidic to an alkaline state and significantly enhancing CO2 sequestration.