Modulation of starch-based film properties for encapsulation of microbial inoculant

Controlled release of beneficial microorganisms in agriculture by encapsulation in biopolymeric matrices can improve biofertilizer efficacy, but it requires the modulation of properties to ensure more efficient and predictable release patterns. This study investigated the effect of a starch-based system to protect and release Priestia megaterium (former Bacillus megaterium) processed as films modified with potential cell-protective additives (maltodextrin, cellulose, and bentonite). The release kinetics, physicochemical and morphological film characteristics, and their protection against UV (Ultraviolet) radiation and temperature were evaluated. The microorganism release was dependent of the film microstructure and composition, both in initial and extended-release rates. Maltodextrin incorporation increased cell release, while cellulose and bentonite delayed due to influences in the water uptake (swelling) and diffusion across polymer structure. Modified films protected the microorganisms against UV radiation and extreme temperatures, being the film with all additives (SMCB) the best protective formulation (100 % UVC survival) compared to starch matrix (< 20 % UVC survival after 40 min) and the one with the highest viability at higher (54 % survival at 45 °C) and lower (80 % survival at 15 °C) temperatures. These insights pave the way for targeted, efficient, and sustainable biological solutions to agricultural practices, aligning with evolving needs in modern agriculture.