Immobilization of yeast cells with polymeric carrier cross-linked using radiation technique

Various compositions of 2-hydroxyethacrylate (HEA) and methoxy polyethylene glycol methacrylate (M23G) monomers were irradiated by gamma-rays at low temperature (-78 degrees C) to synthesize polymer carriers for effectively immobilizing yeast cells. The yeast cells were immobilized by cell adhesion onto/in these polymers. The ethanol productivity of immobilized yeast cells with the polymer carriers was higher than that of free cells, increasing by 1-3 times. However, the ethanol productivity of immobilized yeast with the polymer carrier resulting from 7%/7% (HEA/M23G) monomer was low, comparatively. The effect of adding cross-linking reagent (4G) to the low concentration of HEA/M23G monomers on the activity of yeast cells immobilized with the cross-linked carriers by radiation polymerization was investigated. The ethanol productivity of immobilized cells with the carriers, which were cross-linked by adding 3-6% 4G to the low concentration of HEA/M23G monomer, was increased by 20-30%, because the pore size, network structure, and mechanical strength of the polymer carriers was well adjusted and cell leakage from the polymer carriers decreased. The relationship between the ethanol productivity of immobilized yeast cells and the interior structure of polymer carriers is discussed and indicated that the interior structure of polymer carriers is crucial for effective immobilization of yeast cells.