Air-Suspension Fluidized-Bed Microencapsulation of Probiotics

Abstract

In the present research, an air-suspension fluidized-bed technique for generation of core and shell microcapsules containing probiotic Lactobacillusparacasei cells was evaluated. The air-suspension process was performed in a Würster coater system with a bottom-spraying atomizer. In the first stage, a solution containing trehalose, maltodextrin, and probiotic cells was spray-coated onto and absorbed by the inert carrier microcrystalline cellulose to produce nonagglomerating dry coated particles with high probiotic cell viability (109 colony-forming units [cfu]/g particles). The effect of inlet air temperature, spray flow rate, solids concentration, cell concentration, and encapsulation formulation on survival was investigated. The inlet air temperature had the most pronounced effect; a 15°C increase in inlet air temperature led to a 250-fold decrease in survival percentage. There was no agglomeration of the coated adsorbed particles at spray flow rates of 1 to 3.5 mL/min. Spraycoating was performed with both laboratory- and pilot-scale Würster systems. Scaling up the equipment from the lab scale to the pilot scale did not affect cell survival percentage. Low solids concentration (<20%) and low probiotic cell concentration (6%) resulted in a fair survival percentage (35–40). Spraying a solution formulation of trehalose–maltodextrin with dextrose equivalent (DE) 3 at a 1:1 ratio provided the best protection in terms of cell viability during the spray-coating process as well during storage. Layering with ethylcellulose (ETHOCEL) provided some protection in a low acidic environment (12%); however, the nonuniform coating and cracks detected by scanning electron microscopy (SEM) imaging were the main reasons for the layering's relatively poor protection of the cells against humidity, oxygen, and acid environment.