PART 3 - Kinetics of Substrate Utilization, Product Formation and Biomass Production in Cell Cultures

Question 1

Under Endogenous and Maintenance Metabolism:

5 Limitations of Monod model

Answer 1

1. At high substrate concentration, the maximum specific growth rate is independent of the substrate concentration. This is because the microorganisms have already reached their maximum growth rate and cannot utilize the excess substrate efficiently.
2. At low substrate concentration, growth is dependent on substrate concentration. This means that as the substrate concentration increases, the growth rate also increases, up to a certain point where the growth rate reaches its maximum value (μmax).
3. The Monod model cannot be applied when a substrate exhibits inhibition. Toxic substrate that can be found in industrial wastewater can hinder bacteria growth and substrate consumption.
4. The Monod model does not account for the fact that cells may require substrate for
   maintenance during the death phase.
5. The Monod model does not account for the lag and death phase during the growth phase.

Question 2

Refers to the metabolic activities that occur when cells utilize their own intracellular components as a source of energy and carbon in the absence of external nutrients.

Answer 2

Endogenous metabolism

Question 3

This metabolism is a subset of
endogenous metabolism. It specifically refers to the metabolic processes and energy requirements necessary to keep a microorganism alive and functioning when it is
not actively growing or dividing.

Answer 3

Maintenance metabolism

Question 4

Typically occurs in the stationary phase of growth or when external nutrients are exhausted. Cells start to degrade their own storage compounds or cellular components,
such as proteins and lipids, to survive.

Answer 4

Endogenous metabolism

Question 5

It includes activities like maintaining
membrane potential, repairing cellular damage, synthesizing essential molecules (enzymes, ribosomes, etc.), and other cellular maintenance tasks

Answer 5

Maintenance metabolism

Question 6

This can lead to cell death over prolonged periods since cells are essentially eating themselves.

Answer 6

Endogenous metabolism

Question 7

This metabolism is often quantified
in terms of the rate of substrate utilization (e.g., the rate of oxygen consumption or substrate
consumption) by microorganisms when they are not growing.

Answer 7

Maintenance metabolism

Question 8

Endogenous metabolic needs are often growth-_______________.

Answer 8

independent.

Question 9

Cell maintenance is cell growth-.

Answer 9

dependent

Question 10

At ___________________of substrate or product and in the presence of inhibitory substances in
the medium, growth becomes inhibited, and growth rate depends on inhibitor concentration.

Answer 10

high concentrations

Question 11

At high substrate concentrations, microbial growth rate is inhibited
by the substrate.

Answer 11

Substrate Inhibition

Question 11

High concentrations of product can be inhibitory for microbial growth.

Answer 11

Product Inhibition

Question 11

________________________ is a good example of noncompetitive product inhibition, and ethanol is the inhibitor at concentrations above about ____.

Answer 11

Ethanol fermentation from glucose by yeasts
5%

Question 12

The following rate expressions are used for competitive, noncompetitive, and uncompetitive inhibition of growth in analogy to enzyme inhibition.

Answer 12

Inhibition by toxic compounds

Question 13

In some cases, the presence of toxic compounds in the medium results in the _____________________________.

Answer 13

inactivation of cells
or death.