Emulsion/Cross-Linking Encapsulation of Bacillus in Starch/PVA-Based Microparticles for Agricultural Applications

A major drawback of using Bacillus in the promotion of plant growth is the loss of viability under adverse field conditions and during storage. Here, we propose an encapsulation strategy using an emulsion/cross-linking technique with a starch/poly(vinyl alcohol) (PVA)-based matrix for enhancing the cell viability of Bacillus megaterium. The cross-linking agent, trisodium trimetaphosphate (STMP), combined with either starch (ST) or montmorillonite (MMT), allowed the formation of microparticles (ST/PVA-STMP + ST and ST/PVA-STMP + MMT, respectively). Characterization was performed using Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and scanning electron microscopy (SEM). Both microparticles exhibited cell viability higher than 10.75 log₁₀ CFU g^–1 after the encapsulation procedure. When exposed to heat and fungicide stresses, the microparticles showed a protective role, maintaining cell viability around 9.5 log₁₀ CFU g^–1. The encapsulation also proved advantageous in the accelerated shelf-life test (ASLT) assay, meeting the commercialization requirements of different countries. These findings highlight the potential of the encapsulation procedure to expand the use of microbial inoculants for sustainable agriculture.