Complex growth dynamics in batch cultures: experiments and cybernetic models.

The cybernetic framework developed by Ramkrishna and co-workers is shown to encompass the regulation of nutrient transport processes as well as the effect of nutrient transport on the biotic phase. A structured model which accounts for both an abiotic or environmental phase and a biotic or cellular phase is proposed to describe bacterial growth on lactose as the limiting carbon and energy source. In the presence of lactose, competing uptake mechanisms are proposed. At low lactose concentrations, an energy-requiring transport process is the preferred uptake mechanism. The coupling between cellular energetics and nutrient uptake results in an interesting intermittent growth phenomenon. As the concentration of lactose increases, a nonenergetic transport process is preferred and cellular growth ceases to be intermittent. Model simulations are compared with previously reported experimental results and exhibit good agreement over the entire range of initial lactose concentrations.