CYBERNETIC MODELING OF BACTERIAL CULTURES AT LOW GROWTH RATES
Abstract
The behavior of bacterial cultures at low growth rates was investigated from a cybernetic perspective. The cybernetic view of growth holds that microorganisms use their internal regulatory machinery to steer themselves toward some goal. Identification of this goal circumvents the detailed description of cellular metabolism while simultaneously recognizing the opportunistic characteristics of bacteria. Certain phenomena that are not detectable at high growth rates become significant at lower rates. In particular, cellular maintenance energy needs may drastically affect growth yields. This issue is addressed from a cybernetic perspective for both single- and mixed-substance systems. Experimental data were obtained for the growth of the bacterium Klebsiella oxytoca on various sugars in both continuous and fed-batch cultures. Perturbed fed-batch culture experiments were also performed in order to test the ability of the model to predict highly transient behavior. In all cases, reasonable agreement of the model with the data was observed. Two new concepts that are necessary to predict the transient behavior of bacterial cultures were introduced into the cybernetic framework. The existence of constitutive enzyme-synthesis systems and a growth-rate dependent critical resource must be recognized in order to predict dynamic behavior in a number of systems. Simple rate expressions were developed to model these effects, and incorporation of them into the cybernetic model is described.
Degree
Ph.D.
Subject Area
Chemical engineering
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