Influence of Dissolved Oxygen on Metabolism of Glutamic Acid Biosynthesis by Corynebacterium Glutamicum

Corynehacterium Glutarnicum was cultivated in three parallel 5 L fermenters under 0,5% and 30%dissolved oxygen concentrations,respectively.The metabolism response of Corynehacterium Glutamicum to different dissolved oxygen concentrations were investigated systematically.The results showed that as the dissolved oxygen concentration decreased,the concentrations of citrate andα~- oxoglutarate decreased,the concentrations of organic acids in the reductive arm of the TCA cycle as well as the amount of alanine,valine and phenylalanine increased.When the dissolved oxygen concentration was kept at 0,lactate and acetate accumulated largely.By measuring two key enzyme activities and intracellular NADH/NAD~+ ratio under these three conditions,we found that as the dissolved oxygen concentration decreased,glutamate dehydrogenase(GDH)activity decreased,lactate dehydrogenase(LDH)activity increased,intracellular redox potential increased.All these changes caused metabolic shift towards the reductive arm of the TCA cycle under oxygen limited condition,and which finally led to the decline of the yield of glutamate.