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'Citric Acid' in keywords
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1987 (1)
1983 (1)
1Author    W. Lohmann, D. Holz, B. Kiefer, D. SchmidtRequires cookie*
 Title    On the Origin of the Non-Haemic Iron Transferrin ESR Signal: ESR Investigations on Histidine-Iron-Citric Acid Systems  
 Abstract    The nature o f the high spin ferric iron com plex located at g = 4.3 has been investigated by means o f electron spin resonance spectroscopy and polarography. It could be shown that two complexes each exist in the acid and alkaline pH region, and that the iron is bound to two histidines, three citric acids, and probably to one bicarbonate. These results agree well with previous findings according to which the ligand field o f iron should be com posed mainly o f oxygen and nitrogen atoms. Another low-field signal located at g = 3.6 appears in the pH range from 2 to 7 only and exhibits its m axim um where the g = 4.3 signal has its m inim um . Its exact nature is still unknown but it seem s to represent som e interm ediate state o f the ternary F e3+-histidine-citric acid complex. When citric acid is used, the spin concentration seem s to be always larger than in the case o f ascorbic acid. Since the effect obtained with ascorbic acid and citric acid seems to be similar, it may be concluded that the biological function o f both o f the acids might be somehow related to each other. 
  Reference    Z. Naturforsch. 38c, 926—928 (1983); received May 2 1983 
  Published    1983 
  Keywords    ESR, High Spin Ferric Ion Com plex, Citric Acid 
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 TEI-XML for    default:Reihe_C/38/ZNC-1983-38c-0926.pdf 
 Identifier    ZNC-1983-38c-0926 
 Volume    38 
2Author    H. Eikmeier, H. J. RehmRequires cookie*
 Title    Semicontinuous and Continuous Production of Citric Acid with Immobilized Cells of Aspergillus niger  
 Abstract    The citric acid excretion of Ca-alginate-immobilized cells of Aspergillus niger in batch culture decreased with a half-time of approximately 19 days. Reactivation of the biocatalysts by regenera­ tion in growth medium was possible, but it was followed by a submerged sporulation of the fungus, and medium was highly contaminated with free cells. Citric acid production could better be prolonged by semicontinuous cultivation with medium exchange every 7 or 14 days, respective­ ly. After 32 days the remaining activity in semicontinuous culture was 1.4-fold higher than in comparable batch experiments. Similar improvements were obtained with a continuous process at a dilution rate of 0.125 v/v • d, whereby medium efflux 
  Reference    Z. Naturforsch. 42c, 408—413 (1987); received October 1 1986 
  Published    1987 
  Keywords    Aspergillus niger, Immobilized Cells, Citric Acid, Semicontinuous, Continuous 
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 TEI-XML for    default:Reihe_C/42/ZNC-1987-42c-0408.pdf 
 Identifier    ZNC-1987-42c-0408 
 Volume    42