There is increasing interest in using beneficial microorganisms as alternatives to synthetic chemical pesticides and fertilizers in agricultural production. Application of beneficial microorganisms to seeds efficiently places microbial inocula into soil where they will be well positioned to colonize seedling roots and protect against soil-borne diseases and pests. Despite the long history of inoculation of legume seeds with Rhizobia spp. and clear laboratory demonstration that a wide range of other beneficial microorganisms improve crop performance, there are still very few commercially available microbial seed inoculants. Further research is needed before the benefits of a wide range of environmentally sensitive potential seed inoculants can be captured for use in agriculture, ecosystem restoration and bioremediation. There is no single solution to improving the ability of seed inoculants to establish and function consistently in the field. Development of novel formulations that maintain the viability of both inoculant and seed during storage will result from multidisciplinary research in microbial and seed physiology and adjuvant chemistry. In this study, alginate immobilization was used to encapsulate microbes for industrial seed treatment. The technology has been demonstrated to encapsulate and stabilize Pseudomonas fluorescens, Penicilium bileae, and Bradyrhizobium japonicum for biological seed treatment. All encapsulated microbes were stable, showing less than a 1 log decrease in viable cell counts, for at least 8 weeks at room temperature. The encapsulated P. fluorescens formulation was stable as a liquid dispersion on shelf for 6 months, and as a dried, on-seed coating for 4 months. The encapsulated B. japonicum showed no loss in viable cell counts after 8 weeks while the unencapsulated control B. japonicum showed a two-log loss in viable cells at the same time point: a dramatic improvment in stability for a microbe that is particularly sensitive to environmental stresses. The process developed in this work yielded microbe encapsulation efficiencies of approximately 60% for all three microbes. We are improving this efficiency by to minimizing the number of cells lost to the process equipment, and to reduce stresses on the cells to mitigate cell damage. Overall, the results show that this novel technology may be extended to an array of different microbial species for a variety of stabilized on-seed and on-shelf liquid applications.

Encapsulation of biologics for agricultural applications

256th National Meeting (2018)

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