title: Effects of pH and dissolved oxygen on the synthesis of γ-glutamyltranspeptidase from Bacillus subtilis SK 11.004.
abstract: BACKGROUND
  γ-Glutamyltranspeptidase (GGT; EC 2.3.2.2) is a widely distributed enzyme that is of interest in the food industry. In this study the effects of pH and dissolved oxygen (DO) on GGT synthesis from Bacillus subtilis SK 11.004 were investigated.
  
  
  RESULTS
  GGT production increased to 0.5 U mL⁻¹ when the pH value was controlled at 6.5. The control of a single DO level revealed that the highest specific growth rate (3.42 h⁻¹) and GGT production rate (0.40 U g⁻¹ mL⁻¹) were obtained at DO levels of 40 and 10% respectively. To satisfy the different oxygen demands at different stages of cell growth and GGT synthesis, a stage DO level control strategy was designed as follows: 40% from 0 to 4 h, 30% from 4 to 6 h and 10% from 6 to 18 h. Furthermore, the maximum biomass (2.27 g L⁻¹) and GGT production (3.05 U mL⁻¹) could be obtained using a fermentation strategy combining a constant pH value with stage DO level control.
  
  
  CONCLUSIONS
  The proposed fermentation strategy resulted in a 13.7-fold increase in GGT production. This finding should be of great importance for the industrial production of GGT.
authors: State Key Laboratory of Food Science and Technology, Jiangnan University, 1800 Lihu Avenue, 214122 Wuxi, Jiangsu, China; School of Food Science and Technology, Jiangnan University, 1800 Lihu Avenue, 214122 Wuxi, Jiangsu, China.
authors: Weiqiao
authors: W
authors: Li
authors: Bo
authors: B
authors: Jiang
authors: Wanmeng
authors: W
authors: Mu
authors: Ming
authors: M
authors: Miao
authors: Tao
authors: T
authors: Zhang
mesh_terms: D001412:Bacillus subtilis / Q000201:enzymology* / Q000254:growth & development / Q000378:metabolism; D001426:Bacterial Proteins / Q000096:biosynthesis*; D061249:Batch Cell Culture Techniques; D019149:Bioreactors; D004790:Enzyme Induction; D005285:Fermentation; D015964:Gene Expression Regulation, Bacterial; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008954:Models, Biological; D010100:Oxygen / Q000737:chemistry / Q000378:metabolism*; D012995:Solubility; D005723:gamma-Glutamyltransferase / Q000096:biosynthesis*
chemical_list: D001426:Bacterial Proteins; D005723:gamma-Glutamyltransferase; D010100:Oxygen