ORAL DELIVERY IN AQUACULTURE - CONTROLLED-RELEASE OF PROTEINS FROM CHITOSAN-ALGINATE MICROCAPSULES

Potentially, the most useful method of fish vaccination is oral admini stration. However, this technique is presently only partially effectiv e because of the apparent destruction of the vaccine in the fish diges tive system, as well as interaction of the vaccine with the feed compo nents. The authors' approach to this problem was to protect the vaccin e by entrapping it within semti-permeable biocompatible microcapsules. Two bioactive agents - a vaccine, Vibrio bacterin and a model protein , bovine serum albumin (BSA) - were entrapped in chitosan-alginate mic rocapsules by extrusion of a sodium alginate/bioactive agent suspensio n into a CaCl2/chitosan solution. The results of experiments on the ef fects of varying the encapsulation parameters and the presence of enzy mes on the in-vitro release of entrapped bioactive material are presen ted. This technique has been developed as a simple, quick, and inexpen sive method for oral delivery. Capsules may be dried and mixed with fe ed for ease of administration, particularly to young fish which are su sceptible to high mortality from both the disease and harsher vaccinat ion procedures.