Precise control strategy of phosphate to enhance the cell growth and the efficiency of product synthesis in Escherichia coli

Phosphate is one of the key materials for microbial growth and product synthesis.Thus,systematic studies of the changes of phosphate,its change rule and the corresponding relationships between the change rule and the synthetic efficiency of target products help to improve the growth of microorganisms and the efficiency of product synthesis.This will also establish a novel control mode of fermentation processes.In this paper,industrially important Escherichia coli was used as a research object to investigate the change rule of phosphate in the fermentation process as well as analyze the corresponding relationships between the growth of Escherichia coli,enzyme production and phosphate consumption.Subsequently,the production level of lysine decarboxylase was increased by controlling the concentrations of phosphate. Through shake flask fermentation,the highest concentrations of diammonium hydrogen phosphate and potassium dihydrogen phosphate that Escherichia coli cells could tolerate were determined to be 24.00 g / L and 81.00 g / L,respectively.The optimum initial contents of diammonium hydrogen phosphate and potassium dihydrogen phosphate were 1.00 g / L and 10.12 g / L,respectively. Besides,only 1 /2 of the total amounts of diammonium hydrogen phosphate and potassium dihydrogen phosphate was added at the beginning,while the remaining 1 /2 was complemented after 4 hours of fermentation. After cultivated under the optimized conditions,the cell density of recombinant Escherichia coli and the specific activity of lysine decarboxylase were increased by 58.42% and 14.09%,respectively. According to the result,the cell growth and products synthesis of E. coli can be improved by dynamic determination and precise control of the phosphate concentration during the fermentation process.