Rhizobacteria microencapsulation: properties of microparticles obtained by spray-drying

Abstract

Rhizobacteria Pseudomonas fluorescens-putida were microencapsulated in Eudragit by spray-drying. These microparticles are subsequently included in seed coating or pelleting material. The survival of the bacterial cell in microparticles were studied under different levels of relative humidity (RH): 0, 33, 55 and 100%. The protective effects of silica, present in certain formulations, were demonstrated at the relative humidities of 33 and 55%. The release of the encapsulated bacteriawas alsostudied over time. The release was fast, the bacteria being observed at 15min immersion of the Eudragit microparticles in an aqueous-buffer medium at 20oC. This result, related tothe physicochemical character of the coating polymer, showed that water was the triggering element for the release of rhizobacteria. Compatibility studies between two film-forming agents used for seed coatings and the encapsulated bacteria, as well as wettability measures of tableted microparticles, were carried out. The bacterial survival was good with the seed coating agent, Sepiret 1039G, and the wettability measurements of agglomerated microparticles were in accord with the rapid release of the microencapsulated bacteria. The application of microparticles containing rhizobacteria on seeds can now be considered for preliminary trials.

Keywords::

• Microencapsulation Spray-drying Eudragit Rs30d Pseudomonas Fluorescens-putida Bacterial Survival