[Knockout of the hprK gene in B. subtilis CcpA mutant and its influence on riboflavin fermentation]

In Bacillus subtilis , raising the amount of carbon catabolite in vivo would lead to carbon catabolite repression (CCR) and restrain the absorption of glucose. By deleting CcpA the CCR effect could be relieved, but the absorption of glucose remains restrained. The phosphoenol-pyruvate-sugar phosphotransferase system (PTS) is the main glucose transportation system in B. subtilis. HPr protein together with HprK/P participate in the glucose transportation. The HPr protein is phosphorylated at His-15 forming HPr-His-15-P transferring phosphate group from HPr to E II . While HprK/P phosphorylate HPr at Ser-46 forming HPr-Ser-46-P. HPr-Ser-46-P cannot participate in the transportation of glucose. The Knockout of ccpA gene increases the amount of fructose 1,6-bisphosphate(FBP) in vivo. And FBP could activate HPr kinase. So when CcpA is deleted, most part of the HPr will be phosphorylated at Ser-46. Absorpton of glucose is blocked. In this study, by disruption of hprk gene, the obtained B. subtilisZHc/pMX45 reaches the peak riboflavin production of 4.374mg/mL at the optimum glucose concentration of 10%, 19.2% higher than that of B. subtilis24 A1/pMX45 at the optimum glucose concentration of 8%.