An optimal model for microbial growth in a multiple substrate environment: simultaneous and sequential utilization

A comprehensive optimal model has been developed to simulate microbial growth for simultaneous utilization of mixture of three substrate. The optimal strategy used to model microbial growth, which was developed by Venkatesh Et al. (Biotechnology and Bioengineering 56(6) 635-644, 1997) is extended to represent simultaneous and sequential growth phenomenon. The model prediction matches closely with the experimental growth data of Escherichia coli on a mixture of substrates involving glucose and organic acids like lactate, pyruvate and acetate. The model is modified to explain multi-auxic growth with the help of an added constraint to the optimization formulation. The two constraints now represents two levels of control inside the cell. The modified model explains diauxic growth of E. coli on a mixture of glucose and lactose. A major feature of this work is to explain the growth of E. coli on a mixture of glucose, acetate and lactose which displays both sequential and simultaneous utilization of substrates. (C) 1998 Elsevier Science Ltd. All rights reserved.