Microencapsulation of emulsified lipophilic bioactive compounds in dry, cross-linked alginate microcapsules (CLAMs) is a promising strategy to facilitate their incorporation into food systems, prolong shelf life, and target delivery within the gastrointestinal tract. However, current technology to produce CLAMs requires multiple time-and energy-intensive unit operations. We developed a novel technology that streamlines CLAM production into a single unit operation by accomplishing particle formation, cross-linking, and drying during spray-drying. Spray-dried CLAMs were prepared using corn oil as the cargo, and dry basis oil loadings up to 35% (w/w) were achieved. Alginate cross-linking was verified by the insolubility of CLAMs in water and ready dissolution in sodium citrate. Volume weighted mean particle size of CLAMs increased with increasing oil content: 8.1 µm, 11.8 µm and 17.9 µm for 15%, 25% and 35% oil, respectively. Spray dried CLAMs were approximately spherical, with oil droplets evenly distributed throughout each microcapsule. The size distribution of oil droplets, with average diameters ranging from approximately 200 to 300 nm, remained unchanged throughout the encapsulation process; spray drying did not induce aggregation or coalescence of oil droplets within CLAMs. CLAMs released 22-35% of oil in simulated gastric fluid (pH 1.5) and 81-93% in simulated intestinal fluid (pH 7) in 2 hours, indicating that CLAMs are an enteric system. Coupled with the scalability of this novel CLAM production method, the successful encapsulation of the model lipid suggests that spray-dried CLAMs may be of commercial use for incorporating lipophilic compounds into foods.

Microencapsulation of plant-beneficial bacteria, such as pink pigmented facultative methylotrophs (PPFM), may greatly extend the shelf life of these Gram-negative microorganisms and facilitate their application to crops for sustainable agriculture. A species of PPFM designated Methylobacterium radiotolerans was microencapsulated in cross-linked alginate microcapsules (CLAMs) prepared by an innovative and industrially scalable process that achieves polymer cross-linking during spray-drying. PPFM survived the spray-drying microencapsulation process with no significant loss in viable population, and the initial population of PPFM in CLAMs exceeded 1010 CFU/g powder. The PPFM population in CLAMs gradually declined by 4 to 5 log CFU/g over one year of storage. The extent of alginate cross-linking, modulated by adjusting the calcium phosphate content in the spray-dryer feed, did not influence cell viability after spray-drying, viability over storage, or dry particle size. However, particle size measurements and light microscopy of aqueous CLAMs suggest that enhanced crosslinking may limit the release of encapsulated bacteria. This work demonstrates an industrially scalable method for producing alginate-based inoculants that may be suitable for on-seed or foliar spray applications.

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