Fermentation enzymes in strains of Paracoccus denitrificans

Various strains of Paracoccus denitrificans grown under conditions of unrestricted oxygen supply contained low but measurable activities of fermentation enzymes such as ethanol dehydrogenase and 2,3-butanediol dehydrogenase. However, when the bacteria were subsequently incubated for up to 22 h under restricted aeration conditions permitting respiration rates of only 10 or 6% of the maximum value to occur, the above enzymes increased in specific activities by 5- or 10-fold to 0.14 mol/min·mg protein. Lactate dehydrogenase was not detected. Six strains tested reacted almost alike.Cells grown anaerobically on fructose in the presence of limiting concentrations of KNO₃ contained specific activities of up to 0.41 (in case of ethanol dehydrogenase) and 0.56 (butanediol dehydrogenase) mol/min·mg protein. Lactate dehydrogenase was only formed at low activity (0.012 mol/min·mg protein) after a long period of incubation.Cells of P. denitrificans strain Stanier 381 grown anaerobically in the chemostat on fructose+KNO₃ with either fructose or nitrate as the limiting factor differed with respect to the specific enzyme activities, too. Ethanol dehydrogenase was high under conditions of nitrate limitation and low under fructose limitation. 2,3-Butanediol dehydrogenase, but not lactate dehydrogenase, was formed in moderate activities.