A Strategy for Stable, On-Seed Application of a Nitrogen-Fixing Microbial Inoculant by Microencapsulation in Spray-Dried Cross-linked Alginates

Microbial inoculants are environmentally sustainable alternatives to petrochemical-derived herbicides, pesticides, and fertilizers in agriculture. We demonstrated the potential to develop a commercializable Klebsiella variicola product with storage and on-seed stability by encapsulating in cross-linked alginate matrix (CLAM) powder by spray drying. The cross-linked alginate microencapsulation by spray drying ('CLAM process'), an industrially scalable one-step strategy, produced a K. variicola-loaded CLAM with up to ∼1 × 1010 CFU/g powder. The K. variicola-loaded CLAM maintained high viability during encapsulation, slurrying, and adhesion onto seed surfaces (∼7 × 105 CFU/seed) and during ambient storage on corn seeds. K. variicola in CLAM powder maintained long-term (>5 months) viability in controlled environments, such as refrigerated, or oxygen and moisture-free environments. Trehalose with maltodextrin when added to the CLAM successfully extended stability in powder under ambient conditions, while maltodextrin alone had limited impact. Encapsulation in the CLAM maintained K. variicola viability on bare corn seeds with storage stability beyond 3 months.