Analysis of the optimal model for substrate substitutability in continuousmicrobial cultures

A comprehensive model for microbial growth in multiple substrate environmen t developed by Venkatesh et al. (1997, Biotechnol. Bioengng, 56, 635-644) i s applied to growth in continuous cultures and analyzed at steady state. An alytical expressions are derived for substrate concentrations in terms of c ellular and reactor parameters. These expressions are seen to describe the substrate utilization pattern and to identify regions of steady state and w ash-out for a given feed concentration. These expressions also give the nat ure of the isoclines just based on simple manipulation of the model equatio ns. The model predictions were compared with experimental data and were fou nd to match reasonably well. Simulations were also performed to get steady- state concentrations of substrates with varying dilution rate. It was seen that in mixed substrate cultures, the system washes out at higher dilution rates than when they were growing on single substrates. The model was exten ded for microbial growth on various substrate pairs and also on a mixture c ontaining three substrates. (C) 1999 Elsevier Science Ltd. All rights reser ved.