Aerobacter cloacae

When grown in a mineral medium containing KDO as the only source of carbon, cells of Aerobacter cloacae can be induced to produce an enzyme that catalyzes the cleavage of KDO to give D-arabinose and pyruvic acid.89 This enzyme was purified 60-fold by Ghalambor and Heath.154 It has a pH optimum of 7, a KM = 6 mM, and an equilibrium constant of 77 mM. The reversible nature of the enzyme reaction can be utilized to synthesize 14C-labelled KDO from D-arabinose plus 14C-pyruvic acid. Cleavage of KDO as catalyzed by KDO aldolase has... 

Aerobacter cloacae) grown on synthetic KDO [11], but no further use of the enzyme has been reported. 

Herbert et al.(1956) reported that the growth kinetics of Aerobacter cloacae in a chemically defined medium (glycerol as a limiting substrate) could be expressed by Monod kinetics as follows ... 

Early experiments concerned the enzymatic hydrogenation of fumaric acid to succinic acid, catalyzed by either yeast 24,55 or enzyme extracts from yeast cells56. Much later, strains of Escherichia coli, Aerobacter aerogenes and Aerobacter cloacae were shown to have the same ability 57,58. An interesting mixed culture fermentation has been developed, where the fungus Rhizopus chinensis produces fumaric acid from glucose and a selected E. coli converts the previously formed fumaric acid into succinic acid58. 

Herbert et al. (HIO) studied the growth of Aerobacter cloacae in both continuous and batch propagators. The limiting substrate was glycerol. Constants and a were determined from batch data the constant K was determined from the holding time at which productivity was a maximum in continuous propagation—not highly accurate, but the best that could be done under the experimental circumstances. 

Fig. 16. Comparison of Monod s model with data of Herbert et al. (HIO) on growth of Aerobacter cloacae. Solid line calculated from Monod s model with /a = 0.85 hr , K = 0.0123 g/liter, C,f = 2.5 g/liter, and a = 1.89 g/g. Replotted from J. Gen. Microbiol. 14, 601-622 (1956), by permission of Cambridge University Press.

The existence of a specific adaptive 2-ketogluconokinase in Aerobacter cloacae has been briefly reported by De Ley. The nature of the product and its further metabolism would be of considerable interest. 

The 2-keto-3-deoxyoctosonate (KDO) aldolase (KdoA EC 4.1.2.23) is an inducible enzyme in gram-negative microorganisms [78] where d-KDO 8 is a core constituent of the outer membrane lipopolysaccharide. The aldolases from Aerobacter cloacae and an Aureobacterium barkerei strain have been studied for synthetic applications [72,79]. Similar to the NeuA, the KdoA enzyme has a broad substrate specificity for aldoses in place for the natural acceptor D-arabinose (Table 2) while pyruvate was found to be irreplaceable. Preparative applications, e.g., that for the synthesis of KDO analogs 13/14 (Fig. 9), suffer... 

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