Immobilization of cells by macro-porous NaCS-PDMDAAC capsules and cultivation in shaking flask and bubble bioreactor / 生物工程学报

ABSTRACT

The membrane of sodium cellulose sulphate ( NaCS)-poly dimethyldiallylammonium chloride (PDMDAAC) microcapsule is compact and has low molecular weight cut-off, which would delay the mass transfer and affect the cell growth immobilized in the capsule. Macroporous NaCS-PDMDAAC microcapsules were prepared using the degradation of the starch by amylase in the membrane of the capsules. The pore size and the permeability in the membrane were improved obviously. As model cells, the Candida krusei CK1 and E. coli EC1 immobilized in the capsules were cultured in the shake flask and bubble column respectively. It was shown that the cell density immobilized in the microcapsules cultured in the bubble column was higher than that cultured in the shaking flask. It implied that the limiting factor of the cell growth in the capsule lied in the diffusion of the oxygen. Since the rate of the oxygen transporting across the membrane was greatly enhanced due to the enlarged pore size, the maximum cell density in the macroporous capsules was 20%-110% over than that in the standard capsules in the bubble column. However, the extent of E. coli cell density increasing was higher than that of the yeast, which may be due to the difference of the oxygen requirement between the two microbes.