Stability improvement of alpha-amylase entrapped in kappa-carrageenan beads: Physicochemical characterization and optimization using composite index

Purpose: This work examines the influence of various process parameters on alpha-amylase entrapped in crosslinked K-carrageenan beads for stability improvement. A three level full factorial design was employed to investigate the effect of three process variables namely K-carrageenan concentration, potassium chloride concentration and hardening time on % entrapment, time required for 50% (T-50) and 90% (T-90) of enzyme release and particle size. Methods: The beads were prepared by dropping the K-carrageenan-containing alpha-amylase to magnetically stirred potassium chloride solution. The composite index was applied to optimize the process under study. 'In vitro' enzyme release profile of the beads was fitted to various release kinetics models to understand the release mechanism. Topographical characterization was carried out by SEM and entrapment was confirmed by FTIR and DSC. Stability testing according to the ICH guidelines for zone III and IV was carried out. Results: With the use of ionotropic gelation method, a polymeric matrix prepared by 3.5% (w/v) K-carrageenan, 0.7 M potassium chloride and hardening time of 30 min resulted in the production of beads characterized by disc shaped with collapsed center, absence of aggregates, % entrapment of 73.79, T-90 of 74.4 min, and composite index of 83.01. Moreover, shelf-life of the enzyme loaded beads was found to increase up to 3.53 years compared to 0.99 year of the conventional formulation. Conclusions: It can be inferred that the proposed method can be used to prepare alpha-amylase loaded K-carrageenan beads for stability improvement. Also the proper selection of rate-controlling carrageenan concentration and its interactive potential for crosslinking is important and will determine the overall size and shape of beads, the duration and pattern of dissolution profiles and enzyme loading capacity. (c) 2006 Elsevier B.V. All rights reserved.