Applications of Chemical Kinetics in Environmental Systems - Elements of Environmental Engineering: Thermodynamics and Kinetics - page 380

TABLE 6.17
Redox Potentials for Electron
Transport Agents in Biochemical
Systems
Component E H

(V)

NAD + 0.1

Flavoprotein + 0.34

Cytochrome c + 0.69

Oxygen + 1.23

Outer
solution

Membrane Cytoplasm

NADH + H +

NAD +
4H +

Flavoprotein
FeS protein
Co-enzyme Q
Cytochro me b
Cytochrome o

0.5O 2 + 2H +

2H +

H 2 O

4H +

ADP

H +

H +

ATP

FIGURE 6.65 Electron transport and ATP synthesis in a living cell.

6.5.1 E NZYME R EACTORS
Biochemical reactors are used in environmental engineering not only for exsitu waste
treatment operations, but also in situ waste site remediation processes. Those that
employ living cells (producing enzymes) are termed fermentors , whereas those that
involve only enzymes are called enzyme reactors . We shall first describe the enzyme
reactor, but the reader is reminded that the same principles are also applicable to
fermentors (Bailey and Ollis, 1986; Lee, 1992).
There are three types of enzyme reactors similar to conventional chemical reac-
tors such as described in Section 6.1. These are (i) a batch reactor; (ii) a PFR; and
(iii) a CSTR. In addition, we will also discuss a convenient operational mode appli-
cable to each of the reactors. This is the process of immobilizing (anchoring) the
enzymes so that contact between the enzyme and substrate is facilitated.