大孔型NaCS-PDMDAAC微胶囊固定化细胞在摇床和鼓泡塔中的培养研究

Immobilization of Cells by Macro-porous NaCS-PDMDAAC Capsules and Cultivation in Shaking Flask and Bubble Bioreactor

NaCS-PDMDAAC生物微胶囊囊膜较为致密,影响胶囊内外物质的交换,从而影响胶囊内细胞的生长.利用淀粉酶对致孔剂淀粉的降解作用制备了一种大孔型的纤维素硫酸钠-聚二甲基二烯丙基氯化铵(NaCS-PDMDAAC)生物微胶囊,实验表明胶囊的孔径和通透性能都有了很大的提高.将酵母和大肠杆菌作为模型细胞包埋于胶囊中分别通过摇瓶和鼓泡塔半连续培养,在鼓泡塔中胶囊内细胞的密度要高于摇床,表明氧气的传递是胶囊内好氧细胞生长的限制因素,大孔胶囊由于囊膜孔径变大,氧气的传递更为快速,在鼓泡塔中大孔型胶囊内的最大细胞密度比常规胶囊要高出20%～110%.由于对氧气的需求量的不同,大肠杆菌菌浓提高的程度要高于酵母.

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.