Comparing Fluidized Bed Spray-Coating and Spray-Drying Encapsulation of Non-Spore-Forming Gram-Negative Bacteria

Abstract

10 Microencapsulation of plant-beneficial bacteria for use as biopesticides is a growing area of 11 interest in the search for alternatives to harmful chemical pesticides. In this study, we assessed 12 the microencapsulation of the Gram-negative, non-spore-forming plant-beneficial bacterial strain 13 Collimonas arenae Cal35 in novel cross-linked alginate microcapsules (CLAMs) formed by 14 spray-drying, and in novel cross-linked alginate matrix shell (CLAMshell) particles formed by 15 fluidized bed spray-coating. Survival of Cal35 was 10-fold greater in CLAMs than in 16 CLAMshells. During individual stress tests, Cal35 was found to be more tolerant to high 17 temperatures than to desiccation. This is consistent with the greater survival of Cal35 when 18 encapsulated by spray-drying, which is a process that uses high inlet temperature and short 19 exposure times to dry conditions. The particle diameter of CLAMs ranged from 5 to 20 µm, 20 indicating potential for spray applications. CLAMshell particle diameters were between 250 and 21 300 µm, suggesting potential for seed coatings.