Calcium alginate capsules can be easily synthesized by extruding a sodium alginate solution into an aqueous solution of calcium chloride and enable to maintain the biological activity of entrapped living microorganisms. However, these calcium alginate capsules show poor mechanical stability. It is known that alginate is a swelling component which leads over time to leakage of entrapped components, including living cells which can subsequently be released and maybe proliferate in the external medium. Indeed, fractures are observed on the entire bead volume and the strength of the capsule decreases from the surface to the core. Therefore, alginate capsules would seem not to be the appropriate host matrix for the encapsulation of components including living cells.