The Weighted Model fails for Inhibition

The concept of weighting based on nearness to the Monod half-saturation coefficient does not work for inhibitory nutrients. The effect on µ gets worse as the concentration of inhibitory nutrient increases, but our weighting coefficient gives this less weight because we are getting further away from the half-saturation coefficient.

Graph Comparing Double Monod Model with Weighted Model

The double-Monod model is not too bad, except in the region of low nutrient concentrations. However, this is the region of most interest. Our group has proposed an alternative based on this equation:

The final term mimics the approach of the Andrews equation by puting a Ki factor in the denominator. The next applet permits exploration of the effects on the different equations:

Graph Comparing Double Monod Model with Hybrid Model

The hybrid equation gives higher values for the specific growth rate coefficient in the region of low substrate concentrations and would seem preferable to using the double-Monod approach. We need more knowledge about the ways in which microorganism growth rate is established.

This is the end of this presentation.

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