Floating pellets containing bacterial antagonist for control sheath blight of rice: formulations, viability and bacterial release studies

Floating pellets containing spores of bacterial biological control agent, Bacillus megaterium were prepared by extrusion–spheronization process. The formulations composed of hydrogenated vegetable oil (HVO), lactose, microcrystalline cellulose (Avicel® PH101), and a disintegrant; cross-linked sodium carboxymethylcellulose (Ac-Di-Sol®). The finishing pellets contained bacteria ranging from 10 7 to 10 8 CFU/g and the viability of bacteria in all formulations remained high after 6 months storage. The scanning electron microscope (SEM) was used to observe endospores of B. megaterium on both the surface and the inside of the pellets. The formulations were tested for their physical properties, floating ability and bacterial release. The level of disintegrant in the formulations influenced the floating ability and the liberation of antagonistic bacteria from pellets. The bacterial pellets showed promising result in suppression of the development of sheath blight lesions in greenhouse experiment.