Sodium Alginate–Chitosan Microcapsules: Release Profile and Viability of Encapsulated Bifidobacteria

INTRODUCTION. Oral administration of probiotics is limited by their low viability while passing through the harsh gastrointestinal environment. Microencapsulation in the alginate–chitosan system makes it possible to protect bifidobacterial cells and ensure their delivery to the large intestine. However, the effect of chitosan coating on alginate microcapsules and the relationship between the release profiles of model compounds and the viability of encapsulated probiotics remain understudied; this necessitates an experimental comparison of coating parameters, microcapsule size, and their effects on release kinetics and colony-forming unit (CFU) recovery.

AIM. This study aimed to develop guidelines for the design of probiotic dosage forms using Bifidobacterium bifidum as a case.

MATERIALS AND METHODS. A 2% sodium alginate solution containing either sodium metamizole (2%) or bifidobacteria (2.5×10⁶/1.25×10⁶ CFU/mL) was extruded into a 5% CaCl₂ solution to form microcapsules subsequently coated with chitosan (0.4%, pH 6.0) by 0–1,080 min exposure to the coating solution. Capsules were produced using 0.16 and 1.8 mm needles. Dissolution test with stepwise pH change was performed without media replacement; sodium metamizole release was quantified by UV spectrophotometry (λ = 258 nm); bifidobacterial viability was assessed by counting CFU cultivated on MRS-5 agar.

RESULTS. After only 15 min of exposure, chitosan coating markedly reduced early sodium metamizole release in the dissolution test, while further coating produced no relevant additional changes. Bifidobacterial viability was as follows: 0.16 mm needles, without coating, <1%; 0.16 mm needles, with coating, ≈20%; 1.8 mm needles, with coating, ≈50%, at an initial load of 0,5×10⁹ CFU per batch of microcapsules, and ≈80% at 1×10⁹ CFU.

CONCLUSIONS. Short-term exposure of alginate microcapsules in chitosan forms a functional barrier that reduces premature release and increases the viability of microencapsulated probiotics; increasing capsule size further enhances the protective properties of the delivery system. Recommended baseline conditions for large-scale probiotic microencapsulation include chitosan coating with ~15 min exposure (0.4% chitosan, pH 6.0). Large extrusion needles and the final-product package with the high water and oxygen barrier (Alu-Alu blisters or dessicated bottles) is a preferred option for maximum viability and convenient dosing.

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