How Cells Grow - Bioprocess Engineering: Kinetics, Biosystems, Sustainability and Reactor Design - page 580

TABLE 11.4 Oxygen Solubility Interaction Constants at 25 C

H j ,10 L4 m 3 /mol H j ,10 L4 m 3 /mol H j ,10 L4 m 3 /mol

Cation Anion Sugar

H þ OH

7.74 9.41 Glucose 1.19

K þ Cl

5.96 8.44 Lactose 1.97

Na þ CO 2

3

5.50 4.85 Sucrose 1.49

NH 4 SO 2 4

7.20 4.53

NHt 4 NO 3 9.12 8.02

Mg 2 þ HCO 3 3.14 10.58

Ca 2 þ H 2 PO 4

3.30 10.37

Mn 2 þ HPO 2

4

3.11 4.85

PO 3
4

3.20

11.9. EFFECT OF TEMPERATURE

Temperature is an important factor affecting the performance of cells. Table 11.5 shows the
classification of microorganisms according to their temperature optima.
As the temperature is increased toward optimal growth temperature, the growth rate
approximately doubles for every 10 C increase in temperature. Above the optimal temper-
ature range, the growth rate decreases and thermal death may occur. The growth rate
decrease is due in part to the enzymes (protein denaturing) become less active at high
temperatures. The endogenous metabolism or maintenance needs also increase as tempera-
ture is increased beyond optimum range, which leads to a decrease in the apparent biomass
yield.

TABLE 11.5 Classification of Microorganisms Based on Thermal Endurance (after H.W. Blanch and D.S.
Clark. 1996 Biochemical Engineering, Marcel Dekker, Inc.: New York).

Growth temperature range, C

Thermal preference
classification Lower limit Optimum range Upper limit

15 e 18 19 e 22

Psychrophiles 5 (to 5)

30 e 45 35 e 45 Mesophiles 10 (to 15)

Thermophiles 25 45 e 75 60 e 80

Extreme thermophiles 50 60 e 75 75 e 95

Hyperthermophiles 100 and over