Abstract: Response surface methodology was employed to optimize the biosynthesis of cytidine triphosphate (CTP) from cytidine monophosphate (CMP) by immobilized yeast cells. CTP was analyzed by HPLC. Critical phosphate ion and Mg2+ concentrations for CTP synthesis were found and CTP yield was restricted when phosphate ion and Mg2+ were lower than their respective critical concentrations. The optimal CTP synthesis conditions were determined as follows: 20 g of immobilized yeast cells were cultured in 20 mL of 100 mmol/L CMP containing 100 mmol/L glucose, 250 mmol/L phosphate and 15 mmol/L Mg2+ at pH 6.1 for 2 h. Under these conditions, the yield of CTP was up to 67.89%.

Key words: cytidine triphosphate, immobilized yeast, biosynthesis, response surface methodology