Cephalexin synthesis using immobilized Xanthomonas citri cells

For continuous production of cephalexin, whole cells of Xanthomonas citri were immobilized by entrapment in polyacrylamide gel and kappa-carrageenan gel. It wasfound that cells immobilized with kappa-carrageenan showed better thermal stability compared to those immobilized by polyacrylamide gel. The cells immobilized with kappa-carrageenan were treated with glutaraldehyde and hexamethylenediamine to prevent gel destruction during prolonged operation. By immobilizing intact cells, the optimal temperature for the synthetic enzyme reaction shifted higher by 8°C and the optimal pH became broader around 6.2 In continuous operation, the immobilized cells retained better operational stability at 25 than at 37°C, and also showed maximal conversion up to 83% at 25°C.