Enzymes - Bioprocess Engineering: Kinetics, Biosystems, Sustainability and Reactor Design - page 385

8.2. Consider the reversible product-formation reaction in an enzyme-catalyzed
bioreaction:

k 1 k 2

E þ S ES E þ P

% %

k 1 k 2

Develop a rate expression for product formation using the pseudosteady-state approx-
imation and show that

K C ½ ½ S P

r max
K m

r P ¼

1þK m ½ þK P ½ S P

k þ k 2 k þ k 2 k 1 k 2

1 1

where K m ¼ , K P ¼ , K C ¼ , and r max ¼

k 2 [E] 0

k 1 k k

1 k 2 2

8.3. The enzyme-catalyzed aqueous reaction
A

/ products

C A ) with rate in moles/(L $ min) and concentration in
moles/liter. We need to process a stream consisting of 100 mol-A/h at 2 mol/L
substrate A to 95% conversion. Batch operations were chosen. For each batch of oper-
ations, the total preparation time (loading, raising temperature, unloading after reac-
tion, and cleaning) is 5 h. Calculate the reactor volumes required.
8.4. We wish to treat 10 L/min of liquid feed containing 1 mol-A/L to 99% conversion. The
reaction stoichiometry is given by

has a rate r ¼ 1.2 C A /(0.01 þ

k 1 C A
K m þC A

2 þ ; r¼

A / R U

0.5 moles $ liter 1 $ min 1 and K m ¼

0.2 mol/L. Suggest a good arrangement
for doing this using two CSTRs. Find the sizes of the two units needed.
8.5. Enzyme E catalyzes the aqueous decomposition of substrate A to products R and B as
follows:

where k 1 ¼

r ¼ 200C A C E0
0:1þC A

enzyme R

A ! þ B ;

$ min 1 and C A and C E0 are in mol/L. The reaction is to carry out
in a plug flow reactor. In the feed stream, the concentrations of the enzyme and
substrate A are 0.001 and 10 mol/L, respectively. How does density change in the
reactor? Find the space time and mean residence time required to drop the substrate
concentration to 0.025 mol/L.
8.6. The enzyme-catalyzed aqueous reaction

where r is in mol $ L 1

A / products

C A ) with rate in moles/(L min) and concentration in moles/
liter. We need to process 100 mol/h of 2 mol/L feed to 95% conversion. Calculate the
reactor volumes required if the reactor system were consisted of
(a) a PFR,
(b) a CSTR,

has a rate r ¼ 2 C A /(0.01 þ