Spray drying of phosphate-solubilizing bacteria for production of new biofertilizers

Phosphate-solubilizing bacteria represent a sustainable solution to cope with phosphorus unavailability in agricultural soil. However, the success of their application is highly dependent on multiple environmental factors, and a novel approach is needed for bioformulations. The present study aimed to evaluate the suitability of the spray drying method for encapsulation of phosphate-solubilizing bacteria Azotobacter chroococcum F14/2, Bacillus megaterium 11/3, and Pseudomonas putida P1. Three strains were characterized, grown under optimal conditions, and encapsulated as a whole medium-cell system using the spray drying method and maltodextrin as carrier material. The described procedure provided encapsulates with an average particle size below 5 ?m, moisture content under 10%, and satisfactory powder properties. The cell viability of encapsulates (after storage) was in the following order: Bacillus megaterium 11/3 > Azotobacter chroococcum F14/2 > Pseudomonas putida P1. Additional protection during spray drying was most probably achieved by the presence of microbial exopolysaccharides, which opened the possibilities for further optimization of encapsulation procedures.