Stabilization of microbial strains in long-lasting double emulsions as a new strategy for liquid biofertilizer formulation

The need for innovative biofertilizers has been increasing in recent years as a consequence of the loss of soil microbial biodiversity. In this context, symbiotic agriculture, which involves the application of beneficial microorganisms to the soil, is an emerging and promising reality. A key point is related to the choice of an adequate formulation strategy for the microbial systems to maintain their vitality and shelf-life. The use of a liquid formulation is an alternative to the traditional dry powders, but currently a successful microbial stabilization in a liquid biofertilizer is still not available. Therefore, the aim of this study is to stabilize different microorganisms using a double emulsion to obtain a liquid product. The emulsion formulation and production conditions were optimized for strain encapsulation and emulsions were characterized by analysing droplet size distribution, concentration, vitality of microorganisms after the production process, and stability of the product over time. A final formulation, obtained by mixing the different emulsions was developed with the objective of delivering a complete pool of beneficial microorganisms to the soil. The mixture was stable for 5 months at room temperature and microorganism concentration remained constant, indicating that no antagonistic activity within the microbial consortium was present.