Determination of the Ks values during the growth of Alcaligenes eutrophus on phenol, 2,4-dichlorophenoxyacetic acid and fructose

The determination of the K_S values presented here is based on the estimation of the stationary substrate concentrations in continuous cultivation experiments. The separation of biomass from the suspension was performed by an ultrafiltration step which succeeded within one second. The decay of substrate concentration during sampling was calculated to amount to less than 6% of the stationary substrate concentration at relevant growth rates. The K_S values derived from these reduced substrate concentrations deviated by only 10% from the theoretical values at a biomass concentration of about 1 g/1. Thus relevant kinetic parameters can be calculated from the data obtained by this procedure. Values of 11, 59 and 14 μM were obtained with 2,4-dichlorophenoxyacetic acid (2,4-D), phenol and fructose, respectively. Similar K_S values were derived with 2,4-D and fructose by using a respirationbased determination for reasons of comparison. With phenol this value was only 7 μM which is as cribed to a physiological background.