Transient sensitivity analysis of a cybernetic model of microbial growth on two substrates

Abstract

When a microbe has a choice of two substrates for its growth in a fermentation medium, its preference varies with the substrates and with time. This``informed'' choice is conveniently expressed by cybernetic models. For the growth of Klebsiella oxytoca in a medium of glucose and lactose, a one-parameter cybernetic model of growth has been employed in a batch bioreactor to analyse sensitivity of the fermentation to perturbations in the parameter, a (0 £ a £ 1). The sensitivity surfaces in the (a-time) space show interesting variations which are discussed. An important observation is that while growth is best promoted with a 1, i.e. sequential consumption of the substrates [8], low sensitivities require smaller values of a, i.e. simultaneous utilisation. Thus, in a realistic operation it may be necessary to compromise between high growth (with subsequent high productivity) and low sensitivity.

Response coefficient analysis of a fed-batch bioreactor to dissolved oxygen perturbation in complementary cultures during PHB production

“…Thus, in a production situation a pragmatic approach might require operating at a sub-optimal Pe to improve reactor stability even at the cost of some productivity loss. A similar observation for another two-substrate system, Klebsiella oxytoca cultivated on glucose and lactose [ 29 ], suggests that this kind of compromise between productivity and sensitivity may have general validity. The existence of a finite value of Pe that offers such a balance has significant practical utility as it enables the naturally present incomplete dispersion in large bioreactors to be gainfully exploited.…”

“…Therefore a disturbance in the DO concentration is likely to have a smaller effect on the former two than on the latter pair of variables. The possibility of large variables to function effectively as inertial sinks for disturbances is supported by similar observations with Klebsiella oxytoca [ 29 ] and Escherichia coli [ 30 ] cultures.…”

Sensitivity analysis and parameter estimation in a model of anaerobic waste water treatment processes with substrate inhibition

“…Although sensitivity theory has been employed extensively for chemical reactors, its role in biological reactions is of recent origin [10,11]. This theory suggests a tool for investigating the in¯uence of the parameters and that is why it can be used for solving the parameter estimation problem [20,21].…”