Isolation and screening of silicate-solubilizing bacteria for enhanced desilicification of silica-containing...

Silica solubilizing bacteria (SSB) play a vital role in the silicon (Si) cycle by producing the enzyme silicase, which converts insoluble silicates into bioavailable silicic acid, replenishing bio-available Si in soil. Si, a beneficial element for silica-rich plants, is depleted annually due to plants uptake, intensive agriculture, and slow silicate bio-weathering. This study aims to isolate novel SSB with an enhanced silicate desilicification potential from rice field soil. Primary screening for silica solubilization ability was performed on silicate glucose agar (SGA). The selected bacterial strain was evaluated for silicase production under submerged fermentation (SmF) condition using a modified Horikoshi medium. Then, molecular identification was performed by 16S rRNA sequencing analysis and confirmed for silicic acid formation by FTIR-ATR analysis. The investigation resulted with a bacterial isolate forming a clear zone with a solubilization index (SI) of 3.3. Subsequently, 16S rRNA gene sequencing analysis confirmed the isolate as Etopseudomonas mendocina. Further a comparative silicase activity of the bacterial isolate showed its maximum activity of 1.67 ± 0.06U/mL on in rice husk against other agro residues viz, rice straw, wheat husk and wheat straw. FTIR-ATR analyses confirmed the presence of silicic acid in the crude extracts of the agro residues after culture with the bacterial isolate, with characteristic peaks at 3400-3200, 1600-1650, and 1100-1300 cm^-1. The research findings reveal that the bacterial isolate effectively biodegrade silica-rich agricultural residues and may have potential applications in agro-residue management. These degradative products could be used as Si-based biofertilizers for sustainable agricultural practices.