Further characterization of L-leucine-pyruvate transaminase from Acetobacter suboxydans.

L-Leucine-pyruvate transaminase obtained from Acetobacter suboxydans exhibited absorbance maxima to 280 and 332 nm. The 332 nm peak was derived from the coenzyme bound to the enzyme protein with the epsilon NH2 of a lysine residue. The transaminase showed reactivity against many L-amino acids. The relation between the reactivity and the structure of the amino donor is discussed. The Michaelis constants for L-leucine, pyruvate, L-alanine and alpha-ketoisocaproate were 6.7, 3.1, 7.1 and 0.9 mM, respectively. The equilibrium constant was 5.3. The activation energy at pH 5.0 was 8,800 cal/mol.     

Influence of Product Addition on the Oxidation of D-Sorbitol to L-Sorbose by the Strain Acetobacter suboxydans

The kinetics of the D-sorbitol to L-sorbose biotransformation catalysed by the strain Acetobacter suboxydans is studied. The product inhibits the bacterial growth but the transformation is an autocatalytic process. However, higher initial concentrations of sorbose lead to a considerable decrease of the rate constant of the reaction, although the autocatalytic process takes place too. The addition of sorbose in the exponential phase of bacterial growth, or in the stationary phase, leads to a considerable shortening of the process duration, compared to the traditional fermentation.

The rate constants calculated from the kinetic curves are dependent on the initial dry substances concentration and there is a correlation between these levels and the biomass concentration in the stationary phase.     

Biphasic Growth of Acetobacter suboxydans on a Glycerol-Limiting Medium

Dihydroxyacetone was quantitatively produced from glycerol during the primary exponential growth phase and depleted during the secondary exponential phase. Although no growth was detected on the basal medium, growth occurred upon addition of dihydroxyacetone.     

Preparation and Activity of Immobilized Acetobacter suboxydans Cells

The possibility of immobilization of Acetobacter suboxydans cells by entrapment within polyacrylamide gels or by intercellular cross-linking with glutaral-dehyde was investigated. The oxidation of unsubstituted alditols and aldose diethyl dithioacetals by the resultant modified cells has been achieved.