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

Abstract

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.

Encapsulation of Plant Growth-Promoting Bacteria in Poly(itaconic acid) Microspheres by Spray Drying

“…For example, alginate beads are easily colonized and utilized as a nutrient source by soil fungi . While sodium alginate is the most common biopolymer used for encapsulation and can also be spray-dried, it is usually cross-linked in the presence of calcium ions. ,, Poly­(itaconic acid) (PIA) is a biobased polyanionic polymer prepared from the polymerization of itaconic acid (IA), − a double-bond bearing dicarboxylic acid compound, which is mainly produced by microbial fermentation of corn starch and other sugars. PIA is a renewable alternative to compete with petroleum-based poly­(acrylic acid) and polyacrylamide absorbent materials and industrial resins.…”

“…In this study, we have used PIA, synthesized from the FRP of IA, to encapsulate two PGPB, Bacillus subtilis and Pseudomonas fluorescens , using spray drying to produce dry formulations containing active PGPB. The rationale for encapsulation of PGPB in PIA was to look at a polymeric alternative with better chemical stability, as compared to natural biopolymers , commonly used for bioencapsulation, as well as have an alternative to the commonly utilized sodium alginate. The benefits of addition of the vinyl polymer to a microbial inoculum formulation should be more pronounced in agricultural seed treatment applications, where several natural materials lack the desired physical properties for a durable and stable coat formation.…”

Numerical and Experimental Analysis of the Vacuum Corn Seed Degassing System

“…Physical treatments are challenging to implement as there is a delicate balance between effectively eradicating seed-transmitted diseases and causing harm to the seeds [14,17]. Not all seed batches react the same way to all treatments, making it difficult to predict how physical treatments will affect seed germination and vigor [5,7,8,16,18]. Chemical treatments that do not have phytotoxic effects on seeds are available, but methods for complete internal penetration have not been identified [14,17].…”

“…Treating seeds in vacuum chambers is commonly used in agricultural and horticultural settings to improve seed quality and germination rates, leading to enhanced crop yields and plant health [6,11,13,18]. However, it is crucial to ensure that seed treatment is carried out with appropriate equipment and under controlled conditions to avoid seed damage or the onset of undesirable negative effects.…”

“…The absence of particles in a vacuum makes it impossible to measure the usual temperature of air, as there are no particles to generate thermal motion or interact with a thermometer. There are only concepts related to radiation and radiant temperature, which are different from the air temperature encountered under normal conditions [18].…”