Nocardia tartaricans cells immobilized in sodium alginate–cellulose sulfate–poly (methylene‐co‐guanidine)capsules: mechanical resistance and operational stability

The stereospecific hydrolysis of cis‐epoxysuccinate (CES) to L‐(+)‐tartrate, catalysed by the action of CES hydrolase activity in whole Nocardia tartaricans bacterial cells, has been chosen as a model biotransformation system. The performance of cells was studied by immobilization in polyelectrolyte complex (sodium alginate–cellulose sulfate–poly(methylene‐co‐guanidine, SA–CS/PMCG) capsules based on sodium alginate and cellulose sulfate as polyanions, poly(methylene‐co‐guanidine) as polycation, CaCl2 as gelling agent and NaCl as antigelling agent. The encapsulated cells showed a preservation of 80% of the initial catalytic activity in encapsulated cells compared with 15% of retained catalytic activity in free cells after 10 repeated biotransformation cycles. Uniformity of batches of capsules was achieved by the use of an air‐stripping extrusion device fitted with a multiloop reactor. The capsules produced using this device had narrow standard deviations for capsule diameter (<3%) and membrane thickness (<6%). Monodisperse capsules are essential to ensure constant properties, including mechanical resistance and diffusional characteristics. Storage of capsules under different conditions revealed an approximate three‐fold decrease in bursting force after long‐term exposure to the highly sequestering CES, compared with capsules stored in 0.9% (w/v) NaCl. The molecular weight cut‐off of the capsular membrane, determined by inverse size exclusion chromatography, is in the range of the size of CES hydrolase.