Chitosan-alginate coacervate capsules

Figure 1. Simplified protocol of chitosan/alginate or alginate/ chitosan complex coacervate capsule formation (adapted from 10,20,22). ...

Plant cell cultures represent a potentially rich source of secondary metabolites of commercial importance and have been shown to produce them in higher concentrations than the related intact plants. However, plant cell cultures often produce metabolites in lower concentrations than desired and commonly store them intracellularly. These limitations can be overcome by product yield enhancement procedures, including immobilization of cultured cells, and permeabilization, or ideally using a combined immobilization/ permeabilization process with retained plant cell viability. Complex coacervate capsules consisting of chitosan and alginate or carrageenan proved to be effective biomaterials for entrapment, controlled permeabilization of cells and to allow control of capsule membrane diffusivity. 

Beaumont and Knorr (ID) described the detrimental effect of chitosan on cell viability of Apium graveolens. Later it was found that at chitosan concentrations <250 yg/mL (Beaumont, M. and Knorr, D., Univ. of Delaware, unpublished data), plant cell viability was retained. Development of complex coacervate capsules consisting of alginate chitosan (22) and kappa-carrageenan-chitosan (10) allowed the concurrent release of secondary metabolites while still maintaining reasonable cell viability. Chitosan comprised the outer layer of the gel capsule and chitosan diffusivity could be controlled via capsule membrane permeability. 

Daly, M.M. and Knorr, D. (1988) Chitosan-alginate complex coacervate capsules effects of calcium chloride, plasticizers, and polyelectrolytes on mechanical stability. Biotechnology Progress, 4,76—81. 

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