Experimental and modeling study of diauxic lag of Pseudomonas denitrificans switching from oxic to anoxic conditions.

We have shown that Pseudomonas denitrificans undergo a diauxie when switching from dissolved oxygen to nitrate as terminal electron acceptor. The length of time under aeration significantly affected the length of the diauxic lag, whereas the presence or absence of nitrate in the culture under aeration had a marginal effect. Nitrate consumption was very low during the lag period and then increased rapidly, coinciding with exponentially increasing biomass concentrations. Biochemical rate expressions that account for enzyme synthesis and activity in response to culture conditions and enzyme specific levels were developed. The new model successfully predicts the different lengths of diauxic lags observed in the experiments as well as the growth pattern and nitrate uptake.