Preparation of macroporous sodium cellulose sulphate/poly(dimethyldiallylammonium chloride) capsules and their characteristics

Macroporous capsules composed by sodium cellulose sulphate (NaCS) and poly(dimethyldiallylammonium chloride) (PDMDAAC) were prepared by the addition of pore forming agent starch in the encapsulation solution. The starch was firstly immobilized in the membrane of the capsules and then degraded by amylase. The molecular weight cut-off (MWCO) of the macroporous capsules was about 70 kDa for globular proteins, which was about five times larger than that of capsules prepared by standard method. Correspondingly, the mass transfer behavior of the capsules improved significantly, especially for the substances with relatively higher molecular weight. Moreover, the characteristics of the macroporous capsules, such as mechanical strength, size and the thickness of the membrane remained nearly the same as those of the standard capsules. When the macroporous capsules were applied in the immobilization of yeast, the cell density inside these capsules increased 20% than that inside the standard capsules.