Unraveling the biochemical and kinetic mechanisms of potassium solubilization from biotite by a Burkholderia strain.

Potassium solubilizing bacteria (KSB) represent a sustainable strategy for enhancing soil K bioavailability through the dissolution of K-bearing minerals, thereby facilitating nutrient cycling. However, the multifaceted biochemical mechanisms driving mineral weathering remain partially understood. The present study explores the K solubilization characteristic and mechanisms of KSB by analyzing the organic acids they metabolize and their interactions with mineral surfaces. Over 30 d, the strain S1 classified to genus Burkholderia achieved a maximum soluble K+ concentration of 39.8 mg/L, representing a 4.5-fold increase over abiotic controls. Mechanistic analysis revealed a synergistic "dual-attack" strategy: continuous acidification (pH 6.42 to 3.82) promoted proton-driven K+ release, while the dominant secretion of citric and malic acids facilitated ligand-mediated complexation of structural cations, destabilizing the aluminosilicate framework. Additionally, the temporal accumulation of polar and acidic amino acids likely served as biogenic regulators, enhancing bacteria-mineral adhesion and interface interactions. Scanning electron microscopy corroborated these chemical findings, revealing extensive surface etch pits and edge exfoliation. These results suggest that the synergistic interaction of proton attack, ligand-mediated chelation, and amino acid-assisted micro-environment regulation drives mineral weathering. This study provides a comprehensive structural framework for KSB-mediated nutrient mobilization, highlighting the potential of Burkholderia as an efficient bio-fertilizer for potassium-deficient soils.