Dissolution Kinetics of Partially Purified Bromelain From Pineapple Cores (Ananas Comosus [L.] Merr.) Encapsulated in Glutaraldehyde-Crosslinked Alginate-Guar Gum

Abstract

Objective: Bromelain is susceptible to low pH and thus must be encapsulated in glutaraldehyde-crosslinked alginate-guar gum (Alg-GG) hydrogels to avoid bromelain activity degradation in the stomach.
 Methods: Isolated crude bromelain was purified through ammonium sulfate precipitation, sodium benzoate precipitation, and dialysis. Bromelain-loaded Alg-GG was dissolved in artificial gastric fluid and intestinal environment.
 Results: The bromelain fractions showed a higher specific activity (U/mg) than the crude enzyme (51.32), as follows ammonium sulfate fraction (267.70±4.67), sodium benzoate fraction (115.63±3.35), and dialysis fraction (332.22). The dialysis fraction was encapsulated in Alg-GG hydrogel containing 0.75% (v/v) glutaraldehyde through the post-loading method. The swelling ratios of the hydrogel are 188.43% at pH 1.2 and 563.83% at pH 7.4. The highest encapsulation efficiency is 72.2%. The maximum bromelain concentration released during dissolution is higher in artificial intestinal environment (1.97 mg/L) than in artificial gastric fluid (0.18 mg/L), and the maximum proteolytic activities are 1.3 and 0.15 U/mL, respectively. Data were incorporated into the zero-order, first-order, Higuchi, and Korsmeyer–Peppas models to determine the kinetics and mechanism of bromelain dissolution. All bromelain concentrations (70, 140, and 210 ppm) follow the Korsmeyer–Peppas model. The dissolution mechanism is a combination of diffusion and erosion. Both the dialysis fraction (56.59%) and the dissolution product (47.45%) showed a good in vitro antiplatelet activity.
 Conclusion: The present data show the promise of Alg-GG encapsulation as a vehicle for orally administered therapeutic enzymes.