Production and characterization of liquid-core capsules made from cross-linked acrylamide copolymers for...

A novel chemistry has been developed for the production of capsules composed of a hydrophobic liquid core surrounded by a cross-linked polyacrylamide/alginate membrane. These liquid-core capsules may be used in capsular perstraction for the removal of inhibitory products from bioprocesses and bioconversions. They have the advantage of having a high surface area to promote rapid mass transfer, while separation of the organic core phase from the aqueous environment by the capsule membrane prevents the formation of stable emulsions and potential problems associated with toxicity of the organic phase for microbial cells or enzymes. Monodisperse spherical liquid-core capsules of between 800 microm and 1.6 mm diameter, with high mechanical resistance, have been prepared by co-extrusion, using the jet break-up technique. Capsules produced from a solution of MBA/total monomer (5%) were found to be more elastic and have a higher burst force when exposed to chelating agents such as phosphate or citrate. The mechanical resistance was unaffected by buffer solutions in the pH range 4-9 and after sterilization at 121 degrees C for 20 min. Capsules having membranes composed of a copolymer of acrylamide and N-hydroxymethylacrylamide exhibited even higher mechanical stability toward chelating agents.