Phosphorus solubilizing bacteria biofertilizer from native rhizosphere strains

Overview

This research leverages native phosphorus solubilizing bacteria (PSB) to develop biofertilizers that can replace conventional inorganic phosphorus fertilizers. Phosphorus is an essential plant nutrient, yet a large portion of soil phosphorus exists in insoluble, non-labile forms that plants cannot access. The proposed PSB-based biofertilizer addresses this gap by mobilizing soil phosphorus through three complementary mechanisms: solubilization of precipitated phosphorus via pH reduction, chelation of cations to prevent phosphorus precipitation, and enzymatic mineralization of organic phosphorus.

The work is grounded in a collection of 44 bacterial strains isolated from rhizosphere soil samples collected from native Florida plants, including broomsedge bluestem, sawgrass, sword fern, and sea ox-eye daisy. Fifteen of these strains have been identified through 16S rRNA gene sequencing and include species such as Bacillus flexus, Beijerinckia fluminensis, Enterobacter ludwigii, Enterobacter sp., and Pantoea cypripedii. Among these, Enterobacter ludwigii has demonstrated superior phosphorus solubilizing performance.

Technical specifications

Key features:

• 44 phosphorus solubilizing bacteria strains isolated from native plant rhizospheres
• 15 strains identified via 16S rRNA gene sequencing, including Bacillus flexus, Beijerinckia fluminensis, Enterobacter ludwigii, Enterobacter sp., and Pantoea cypripedii
• Strains reduce rhizosphere pH to below 4.27 within seven days of incubation
• Water-soluble phosphorus release up to 588 mg/L under controlled incubation
• Three modes of action: pH reduction for solubilization, chelation to prevent precipitation, and enzymatic mineralization of organic phosphorus
• Enterobacter ludwigii identified as the top-performing strain for phosphorus solubilization

Planned development:

• Test the ability of isolated strains to solubilize organic phosphorus in soils
• Formulate a biofertilizer product by combining the bacterial strains with biochar as a carrier and soil amendment

Technology readiness level

The technology is currently at an early-to-mid stage of laboratory validation. Strain isolation, identification, and initial characterization of phosphorus solubilization activity under controlled incubation conditions have been completed. The next steps involve expanding validation to organic phosphorus solubilization in soil matrices and developing a deliverable biofertilizer formulation by combining the bacteria with biochar. Additional field-scale testing and product formulation optimization will be required before commercial deployment.