Diauxic Growth of Bacteria on Two Substrates

initial concentrations

S

1

, g/L

10

S

2

, g/L

20

X, g/L

0.1

e

1

, g/gdw

0.00005

e

2

, g/gdw

0.00001

parameter values

μ

max,1

,

-1

h

0.9

μ

max,2

,

-1

h

0.6

K

1

, g/L

0.1

K

2

, g/L

0.5

maximum time, hours

15

This Demonstration shows the effect of initial substrate concentrations and initial key enzyme concentrations on the cell growth dynamics in batch cultures. Vary the initial concentrations of the two substrates

S

1

and

S

2

to see if and how the cell growth and substrate consumption dynamics respond. More subtly, vary the initial concentrations (gram per gram cell mass dry weight) of two hypothetical key enzymes

e

1

and

e

2

to simulate the effects of preculturing the inoculum in one or the other of two available substrates.

A more interesting activity on this interactive simulation is to vary the maximum specific growth rates

μ

max,1

and

μ

max,2

on the two individual substrates and observe how these values affect the order in which these substrates are consumed sequentially. Varying the Monod constants

K

1

and

K

2

(also known as saturation constants) has a more subtle effect on the sharpness of the transition to diauxic lag phase or the stationary phase.