Cultivation of yeast and plant cells entrapped in the low-viscous liquid-core of an alginate membrane capsule prepared using polyethylene glycol.

A liquid-core alginate-membrane capsule was prepared by a novel method using polyethylene glycol as a thickener and the cells of Saccharomyces cerevisiae were encapsulated in its core and cultured. After 24 h of cultivation, the cell concentration in the capsule core-liquid reached 222 microg/mm3 on a dry weight basis, which was 1.4 times as large as that in the core of double-layered alginate beads, i.e., alginate-coated alginate-gel beads. The diameter increase of the capsule prepared by the proposed method using immobilized cell growth was suppressed compared to those using the double-layer method and simple alginate-gel bead entrapment, most likely because of the mobility of the entrapped cells in the capsule. We also confirmed that this encapsulation method is applicable for the cultivation of cultured cells of the plant Fragaria ananassa. Additionally, the time-course of the changes in thickener concentration in the liquid-core of the capsule was measured after encapsulation, and revealed the residual thickener, i.e., polyethylene glycol, was able to leak through the alginate shell membrane. This results in low-viscosity of the core liquid enabling good mass-transfer performance, whereas xanthan gum as a thickener could not leak through.