CULTIVATION OF ESCHERICHIA-COLI WITH MIXTURES OF 3-PHENYLPROPIONIC ACID AND GLUCOSE - DYNAMICS OF GROWTH AND SUBSTRATE CONSUMPTION

In technical as well as natural ecosystems, pollutants are often miner alised in the presence of easily degradable carbon sources. A laborato ry model system consisting of Escherichia coli ML 30 growing with mixt ures of 3-phenylpropionic acid (3ppa, 'pollutant') and glucose (easily degradable substrate) was investigated in batch and carbon-limited co ntinuous culture. Untypically, a linear growth pattern was observed du ring batch cultivation with 3ppa as the only carbon/energy source. Whe n exposed to mixtures of both substrates in batch culture, E. coli uti lised the two compounds sequentially. However, 3ppa and glucose were c onsumed simultaneously in continuous culture. Whereas a pulse of exces s glucose to a batch culture growing with 3ppa led to the repression o f 3ppa utilisation, an excess of glucose added into continuous culture did not inhibit the utilisation of 3ppa. During continuous cultivatio n the 3ppa-degrading enzyme system operated close to saturation.