Immobilized Enzymes (Quiz 1)

Question 1

The restriction of enzyme mobility in a fixed space

Answer 1

Enzyme Immobilization

Question 2

Immobilization of enzymes provides Important advantages, (4)

Answer 2

• Enzyme Reutilization
• Elimination of Enzyme Recovery
• Purification processes
• May provide a better environment for enzyme activity.

Question 3

Since some of the intracellular enzymes are ________ Immobilized enzymes provide a model system to __________ the action of some membrane-bound intracellular enzymes.

Answer 3

membrane bound
mimic and understand

Question 4

Product purity is usually improved, and effluent handling problems are minimized by ________

Answer 4

immobilization

Question 5

Methods of Immobilization (2)

Answer 5

• Entrapment
• Surface Immobilization

Question 6

is the physical enclosure of enzymes in a small space

Answer 6

Entrapment

Question 7

Two Major Methods of Entrapment

Answer 7

• Matrix entrapment
• Membrane entrapment, including microencapsulation

Question 8

________ used for enzyme immobilization are usually polymeric materíals such as Ca-alginate,
agar, k- carrageenin, polyacrylamide, and
collagen.

• However, some solid matrices such as activated
  carbon, porous ceramic, and diatomaceous earth
  can also be used for this purpose.

Answer 8

Matrices

Question 9

can be a particle, a membrane, or a fiber.

Answer 9

Matrix

Question 10

______________ of enzymes is possible;
Ex.

• hollow fiber units have been used to entrap an enzyme solution between thin, semipermeable membranes.
• Membranes of nylon,
  cellulose, polysulfone, and polyacrylate are commonly used.
• Configurations, other than hollow fibers, are possible, but in all cases a _______ is used to retain high-molecular weight compounds (enzyme), while allowing small molecular- weight compounds (substrate or products) access to the enzyme

Answer 10

Membrane entrapment
semipermeable membrane

Question 11

A special form of membrane entrapment.

• In this technique, microscopic
  hollow spheres are formed.
• The spheres contain the enzyme solution, while the sphere is enclosed within a porous membrane.
• The membrane can be polymeric or an enriched interfacial phase formed around a microdrop.

Answer 11

Microencapsulation

Question 12

enzyme entrapment may have its inherent problems, such as: (4)

• enzyme _________ into solution
• significant _________
• reduced enzyme ______ and ______
• ________ of microenvironmental conditions

Answer 12

• leakage
• diffusional limitations
• activity and stability
• lack of control

Question 13

____________ can be overcome by reducing the MW cutoff of membranes or the pore size of solid matrices.

Answer 13

Enzyme leakage

Question 14

_________ can be eliminated by reducing the particle size of matrices and/or capsules.

Answer 14

Diffusion limitations

Question 15

_________________ are due to unfavorable microenvironmental conditions, which are difficult to control.

However, by using different matrices and chemical ingredients, by changing processing conditions, and by reducing particle or capsule size, more favorable microenvironmental conditions can be obtained.

Answer 15

Reduced enzyme activity and stability

Question 16

____________ is usually less significant in microcapsules as compared to gel beads.

Answer 16

Diffusion barrier

Question 17

The two major types of immobilization of enzymes on the surfaces of support materials are:

Answer 17

• adsorption
• covalent binding

Question 18

The active site of the adsorbed enzyme is usually unaffected, and nearly full activity is retained upon ________.

Answer 18

adsorption

Question 18

Type of Surface Immobilization:

is the attachment of enzymes on the surfaces of support particles by weak physical forces, such as van der Waals or dispersion forces.

Answer 18

Adsorption

Question 19

_________ of enzymes is a common problem, especially in the presence of strong hydrodynamic forces, since binding forces are weak.

Answer 19

desorption

Question 20

Adsorption of enzymes may be stabilized by cross-linking with ____________. Its treatment can denature some proteins.

Answer 20

glutaraldehyde

Question 21

Support materials used for enzyme adsorption can be:

• _____________, such as alumina, silica, porous glass, ceramics, diatomaceous earth, clay
• _________, or ________, such as
  cellulose (CMC, DEAE-cellulose), starch, activated carbon
• ___________, such as
  Amberlite, Sephadex, and Dowex.

Answer 21

• inorganic materials
• bentonite or organic materials
• ion-exchange resins

Question 22

________________ is the retention of enzymes on support surfaces by ______ bond formation.

Answer 22

Covalent Binding
Covalent

Question 23

Enzyme molecules bind to support material via certain functional groups,

such as ________, _______, ________, and ________ groups.

These functional groups must not be in the active site

Answer 23

• amino
• carboxyl
• hydroxyl
• sulfhydryl

Question 24

One common trick Is to block the active site by ______ the enzyme solution with a competitive inhibitor prior to covalent binding.

Answer 24

flooding

Question 25

Functional groups on support material are usually activated by using chemical reagents, such as:

Answer 25

• cyanogen bromide
• carbodiimide
• glutaraldehyde

Question 26

Two major criteria used in the selection of support material are:

1. the _____ of the support material, which is a function of charge density, functional groups, porosity, and hydrophobicity of the support surface.
2. _____ and ________ of enzymatic activity, which is a function of functional groups on support material and microenvironmental conditions.

Answer 26

1. binding capacity
2. stability and retention

Question 27

If immobilization causes some _______ changes on the enzyme, or if reactive groups on the active site of the enzyme are involved in binding, a ______ in enzyme activity can take place upon immobilization.

Answer 27

conformational
loss

Question 28

Usually, immobilization results in a loss in enzyme activity and stability.

However, in some cases,

Immobilization may cause an increase in enzyme activity and stability due to more favorable
_________. Because enzymes often have more than one _______ that can bind the surface, an immobilized enzyme preparation may be very __________.

Answer 28

microenvironmental conditions
functional site
heterogeneous

Question 29

Even when binding does not _____ enzyme structure, some enzyme can be bound with the active site oriented away from the _____ and toward the ______, decreasing the access of the substrate to the enzyme. __________ of activity varies with the method used.

Answer 29

alter
substrate solution
support surface
Retention