MODULE 3 Lesson 1

Question 1

was one of the most exciting
aspects of biotechnology
during the 1970s.

Answer 1

Cell immobilization

Question 2

Explain Cell immobilization

Answer 2

“the physical confinement
or localization of intact
cells to a specific region of
space, without loss of
desired biological activity.

Question 3

According to Blank, it has been
used as an effective method to improve
the performance and economics of many
fermentation processes.

Answer 3

Zhu (2007)

Question 4

• Cells are encapsulated in an immobilized cell
  system.
• The latter is used when cells are immobilized
  in microcapsules like micrometer-sized
  systems surrounded by a barrier membrane.
• The cell immobilization emerged as an
  alternative for enzyme immobilization

Answer 4

Bioencapsulation

Question 5

• Also referred to as controlled biological catalysts, may be defined as a high density of cells physically confined on a solid phase or in pellets or clumps
• Cell movement is restricted for the period
  of their use as biological agents.
• Has existed or been exploited long before it
  became recognized as potentially valuable in
  industry.

Answer 5

Immobilized Cells

Question 6

Why microbial cells should be immobilized?

Answer 6

Cell immobilization simplifies biomass separation and product recovery, reduces non-productive growth, protects cells from shear forces, allows easier handling and recovery, and produces a cell-free product stream for efficient downstream processing.

Question 7

compare and contrast the immobilized cell fermentation and free cell fermentation

Answer 7

Immobilized cell fermentation is faster and more efficient, achieving high cell density, productivity, and product yield while resisting inhibitory conditions. It allows for continuous processes without cell washout, uses smaller fermenters, simplifies product recovery, and enables cell reuse, ensuring long-term stability and reduced contamination. In contrast, free cell fermentation is slower, less productive, requires larger fermenters, involves complex downstream processing, and cannot reuse cells, making it more prone to contamination and variability.

Question 8

What are the methods for immobilization of microbial cells?

Answer 8

1.Covalent Bonding/ Cross-Linking
2. Entrapment
3. Encapsulation
4. Adsorption

Question 9

The mechanism is based
on covalent bond formation
between activated
inorganic support and cell
in the presence of a binding
or crosslinking agent.

Answer 9

Covalent Bonding/ Cross-Linking

Question 10

are the most common cells used by Covalent Bonding/ Cross-Linking.

Answer 10

Yeast cells

Question 11

Another example of this technique used is
the Blank using ion exchange risen as the material for amylase production.

Answer 11

Bacillus stearothermophilus

Question 12

2 Cross-linking agents Used

Answer 12

• Porous silica beads
• Ion exchange resin

Question 13

• An irreversible technique, where
  immobilized cells are entrapped in a
  support matrix or inside fibers.
• It is to prevent the cells from leaking into
  the surrounding medium while still
  allowing penetration of the substrate.
• Forms a protective barrier around the
  immobilized microbes to ensure
  prolonged cell viability for processing and
  storage.

Answer 13

Entrapment

Question 14

What are the Matrices used?

Answer 14

• Agar,
• Alginate,
• Carrageenan,
• Cellulose and its derivatives,
• Collagen,
• Gelatin

Question 15

• is similar to entrapment that is
  considered an irreversible immobilization
  method.
• In this process, biocatalysts are constrained by
  the membrane walls (usually in a capsule), but
  free-floating within the core space.
• The membrane is semi-permeable that allows
  the free flow of substrates and nutrients. Still,
  the cells are kept inside.

Answer 15

Encapsulation

Question 16

• It is based on the physical interaction between
  the microorganism and the carrier surfaces,
• Reversible, simple, cheap, and effective.
• It stimulates microbial metabolism,
• Protects cells from unfavorable agents and
  preserves their physiological activity.
• is based on weak forces such
  as van der Waals forces, ionic and
  hydrophobic interactions, and hydrogen
  bonds.

Answer 16

Adsorption

Question 17

The key step in controlling the cell
immobilization is both Blank and
Blanks govern the cell support adhesion

Answer 17

electrostatic and hydrophobic interactions

Question 18

What are the Carrier Selection?

Answer 18

• Non-toxic, non-polluting, non-biodegradable
• High cell mass loading capacity
• High mechanical , biological and chemical
  stability.
• Long shelf life.
• Adequate function groups.
• Low-cost price
• Easy separation of cells and carrier from
  media

Question 19

What are the Disadvantages of Immobilized Cells?

Answer 19

Immobilized cells can produce unwanted enzymes alongside the desired ones and may experience genetic changes, though less likely than in traditional fermentation. They risk losing specific catalytic activity, while cells in the core of the flow may suffer from nutrient deprivation or inactivation. Additionally, contamination by other microorganisms remains a concern.

Question 20

Explain the Monolayer attachment, Biofilm formation and Gel entrapment.

Answer 20

The diagram illustrates three mechanisms of cell attachment to surfaces. In monolayer attachment (a), a single layer of cells adheres directly to the surface, forming a thin boundary layer influenced by bulk flow. In biofilm formation (b), cells proliferate and produce extracellular polymeric substances (EPS), creating a thicker, immobilized layer with a distinct boundary layer. In gel entrapment (c), cells or aggregates are immobilized within a polymer matrix on the surface, interacting with bulk flow through a similar boundary layer. These processes are essential in biofilm studies, biotechnology, and environmental applications.