ChE 128 Enzyme Immobilization

Enzyme Immobilization Overview

• Enzyme immobilization confines enzyme solutions within specific spaces to facilitate reuse in processing equipment.
• Various immobilization methods exist, each with unique advantages and disadvantages.

Advantages of Enzyme Immobilization

• Reduces operational costs compared to free enzyme systems which require extra separation and purification steps.
• Certain immobilization techniques can enhance enzyme activity.
• Provides a model system to examine membrane-bound enzyme functions, analogous to those in cellular environments.

Disadvantages of Enzyme Immobilization

• Immobilized enzymes often have reduced activity compared to free enzymes.
• Preparation costs for immobilized enzymes tend to be higher.
• Mass transfer limitations can arise from the immobilization methods used.

Methods of Enzyme Immobilization

• Different techniques for immobilization can influence the efficiency and application of enzymes.

Matrix Entrapment

• Involves mixing enzyme solutions with semi-permeable polymeric materials that solidify into various forms, such as small beads.
• Large molecular weight enzymes remain contained, while smaller substrate and product molecules can diffuse through.
• Common entrapment matrices include:
  • Ca-alginate
  • Agar
  • Polyacrylamide
  • Collagen

Membrane Entrapment

• Enzymes can be confined between thin, semi-permeable membranes made of materials such as:
  • Nylon
  • Cellulose
  • Polysulfone
  • Polyacrylate
• Hollow fiber configuration is a preferred arrangement for separating enzymes from substrates and products.

Surface Immobilization Methods

• Adsorption:
  • Enzymes attach to solid supports through weak physical forces, retaining nearly full activity.
  • Common support materials include:
    • Alumina
    • Silica
    • Porous glass
    • Ceramics
    • Clay
• Covalent Bonding:
  • Enzymes are retained on supports via covalent interactions between functional groups on the enzyme and those on the support.
  • Key functional groups involved in bonding include amino, carboxyl, hydroxyl, and sulfhydryl groups.
  • Covalent bonding must not interfere with the active site; enzyme inhibitors may be added during the bonding process to prevent activity loss.