The Effects Of Rare Earth Ion Ce～(3+) On Growth And Glutamate Fermentation Of Corynebacterium Glutamicum S₉₁₁₄

The effect of rare earth ion Ce³⁺on glutamate production and the critical enzymes ofCorynebacterium glutamicum S9114, which is the most commonly used strain in glutamatefermentation, was investigated in this paper. The infective mechanism of Ce³⁺ on glutamatefermentation was also discussed. Glutamate dehydrogenases (GDH) were purified at the same time.The distribution of REE in the cells was studied. The contents of dissertation were described asfollows.The conditions of flask shaking fermentation were optimized as follows: the culture time ofinoculum 8～10 h, corn steep liquor concentration 1.5%, fermentation volume 10mL, initial sugarconcentration 140g/L, inoculum volume 8%, initial urea concentration 7g/L, K2HPO4 concentration1g/L, feeding 500g/L sugar intermittently after residual sugar dropped to 6%, and feeding sugartime is 10h, feeding 100g/L urea to control pH during fermentation. The temperatures offermentation were, 32³4℃ at prophase, 34³6℃ at metaphase, 37℃ at anaphase. The speed ofrotate were 200r/min at prophase, 250r/min at metaphase, 230r/min at anaphase.The results showed that during glutamate fermentation, the effect of Ce³⁺ on glutamatefermentation was significant. The results showed that Ce³⁺ could increase glutamate concentrationabove 6.0% at the concentration 0.070mmol/L.The enzymes extraction was concentrated 70-fold using the AKTA-100 FPLC system onHiPrep 16/10 DEAE column, Hiprep 16/10 Phenyl (high sub) column and SuperdexG-200 gelfiltration. 0.45 mg GDH was obtained and the specific activity was 248u/mg. Recovery ratio was12%. The enzyme sample has only one band in PAGE, which indicated it had been purified.In order to discuss the mechanism of effect of Ce³⁺ on glumatic acid fermentation, the effect ofCe³⁺ on the growth, critical enzymes of Corynebacterium glutamicum S9114, the enzyme activity ofpurified GDH-NADPH were studied. The results showed that when the Ce³⁺ concentration at lowrange, it could stimulate the growth of Corynebacterium glutamicum S9114, at high range, it coulddecelerate the growth. The Ce³⁺ could obviously increase those activities in the prophase offermentation. The Ce³⁺ could increase activity of GDH-NADPH but reduce activities of LDH andGDH-NADH in certain extent at mid-and later-phase of fermentation. Ce³⁺(0⁰.0070mmol/L)could significantly enhance enzyme activity of GDH-NADPH.The distribution of Ce³⁺ in cells was studied. The results showed that the most of them wereabsorbed on the cell walls, while with a little Ce³⁺ existed in fermentation broth and absorbed on thecell membrane. The Ce³⁺ adhered to the cells increased with the increase of the cultivating time.