Characterization of bioconversion of fumarate to succinate by alginate immobilized Enterococcus faecalis RKY1

In this study, the immobilization characteristics of Enterococcus faecalis RKY1 for succinate production were examined. At first, three natural polyme rs-agar, kappa -carrageenan, and sodium alginate-were tried as immobilizing matrices. Among these, sodium alginate was selected as the best gel for im mobilization of E. faecalis RKY1. Efficient conditions for immobilization w ere established to be with a 2% (w/v) sodium alginate solution and 2-mm-dia meter bead. The bioconversion characteristics of the immobilized cells at v arious pH values and temperatures were examined and compared with those of free cells. The optimum pH anti temperature of the immobilized cells were t he same as for free cells, 7.0 and 38 degreesC respectively, but the conver sion ratio was higher by immobilization for all the other pH and temperatur e conditions tested. When the seed volume of the immobilized cells was adju sted to 10% (v/v), 30 g/L of fumarate was completely converted to succinate (0.973 g/g conversion ratio) after 12 h. In addition, the immobilized cell s maintained a conversion ratio of >0.95 g/g during 4 wk of storage at 4 de greesC in a 2% (w/v) CaCl2 solution. In repetitive bioconversion experiment s, the activity of the immobilized cells decreased linearly according to th e number of times of reuse.