MODULE 3 Lesson 1 Flashcards
was one of the most exciting
aspects of biotechnology
during the 1970s.
Cell immobilization
Explain Cell immobilization
“the physical confinement
or localization of intact
cells to a specific region of
space, without loss of
desired biological activity.
According to Blank, it has been
used as an effective method to improve
the performance and economics of many
fermentation processes.
Zhu (2007)
- 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
Bioencapsulation
- 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.
Immobilized Cells
Why microbial cells should be immobilized?
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.
compare and contrast the immobilized cell fermentation and free cell fermentation
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.
What are the methods for immobilization of microbial cells?
1.Covalent Bonding/ Cross-Linking
2. Entrapment
3. Encapsulation
4. Adsorption
The mechanism is based
on covalent bond formation
between activated
inorganic support and cell
in the presence of a binding
or crosslinking agent.
Covalent Bonding/ Cross-Linking
are the most common cells used by Covalent Bonding/ Cross-Linking.
Yeast cells
Another example of this technique used is
the Blank using ion exchange risen as the material for amylase production.
Bacillus stearothermophilus
2 Cross-linking agents Used
- Porous silica beads
- Ion exchange resin
- 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.
Entrapment
What are the Matrices used?
- Agar,
- Alginate,
- Carrageenan,
- Cellulose and its derivatives,
- Collagen,
- Gelatin
- 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.
Encapsulation
- 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.
Adsorption
The key step in controlling the cell
immobilization is both Blank and
Blanks govern the cell support adhesion
electrostatic and hydrophobic interactions
What are the Carrier Selection?
- 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
What are the Disadvantages of Immobilized Cells?
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.
Explain the Monolayer attachment, Biofilm formation and Gel entrapment.
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.
