The Research Of Glucose Oxidatin Pathway In Klebsiella Pneumoniae

This paper studies the glucose oxidative pathway in Klebsiella pneumoniae. More than 20 single gene mutants and double genes mutants were constructed by gene recombination method. Mutants were inoculated to the M9 medium,with glucose, gluconic acid and 2-ketogluconic acid as the sole carbon source,under the aerobic and anaerobic conditions, to evaluated the growth.Results show that, in aerobic conditions, glucose mainly through the pentose phosphate pathway and glycolytic pathway to metabolism in the intracellular. The two pawthway complement each other.Blocking the two pathways at the same time, glucose can also pass ED ways to metabolism, but the growth is restrained.Glucose acid mainly through the pentose phosphate pathway and the ED pathway to metabolism. 2-ketogluconic acid only has one unique metabolic pathways, that is the pentose phosphate pathway, blocking the metabolic pathway, strains was no longer to growth.Under anaerobic conditions, glucose pass glycolysis pathway to metabolism and glucose acid in the cell has ED way, pentose phosphate pathway and glycolysis pathway to metabolism.The three metabolic pathways complement each other. 2-ketoglucose acid mainly through the pentose phosphate pathway, also through the glycolysis pathway to metabolism.Previous research has found that 2-ketogluconic production by Klebsiella pneumoniae is a p H dependent process. 2-Ketogluconic accumulated at acidic condition. The mechanism of 2-ketogluconic acid production was studied.It was found that 2-ketogluconic acid was synthesized by K.pneumoniae at neutral condition, but it was transported into intracellular.The acid condition inhibit the activity of 2-ketogluconic acid kinase, which cause the accumulation of 2-ketogluconic acid.K. pneumoniaeΔgad, which has lost the activity of gluconate dehydrogenase, was found accumulated gluconic acid at broth. The fermentation parameters was optimized at batch fermentation. It was found that the optimum p H of gluconic acid production was p H 4.5 ~ 5, and the conversion rate can reach 1 g /g. Cell density has letttle effect to the prod-uctivity. However, dissolved oxygen level has a significant impact to gluconic acid produ-ction.The higher the dissolved oxygen, the faster gluconic acid synthesized and a higher conversion ratio was got. But too higher dissolved oxygen, reduce the fermentation last time and avoid gluconic acid accumulated to a higher level. At fed bath fermentation, 422 g/L gluconic acid was produced at 97 h with the conversion ratio 1:1. Gluconic acid production by K. pneumoniaeΔgad has the potential to be used industrial.