Assingment
ERT 211 Biochemical Engineering
Sem 1 2010/2011
Topic : Applied enzyme catalysis
Date of given : 18/8/2010
Date of submission : 27/8/2010 (5 marks will be deduct for 1 day late submission)
Question
1. Draw the structure of starch. Show how amylases cleavage the structure of starch?
[20 marks]
α-amylase
} The action of α-amylase reduces the solution viscosity by acting randomly along the glucose chain at α-1,4 glycosidic bonds
β-amylase
} b-Amylase can attack starch a-1,4 glycosidic bond only on the nonreducing ends of the polymer and always produces maltose when a linear chain is hydrolyzed.
amyloglucosidase
} Another saccharifying enzyme, amyloglucosidase (also called glucoamylase) attacks primarily the nonreducing a-1,4 linkages at the ends of starch, glycogen, dextrins, and maltose. (a-1,6 linkages are cleaved by amyloglucosidase at much lower rates)
2. What is the different between amylose and amylopectin?
[20 Marks]
Amylose is a straight chain glucose polymer that contain -1,4 glycosidic bond
Amylopectin is a branched component of starch that contain β-1,6 glycosidic bond
3. Explain briefly the difference in the chemical structures of amylose and cellulose
[20 Marks]
Cellulose – polysaccharide consisting of a linear chain of several hundred to over ten thousand β-1,4 linked D-glucose units
Amylose is a straight chain glucose polymer that contain -1,4 glycosidic bond
4. Using an appropriate diagram, discuss briefly any two (2) methods of enzyme immobilization
[40 Marks] Adsorption
n 1st enzyme immobilization method
n Attachment of enzymes on the surface of support particles by weak physical forces (eg. van der waals or dispersion force)
n The enzyme molecules get adhered to the surface of support particles on account of the spectacular combination of hydrophobic effects and the critical formation of several salt-linkages per enzyme molecule
n Active site of the adsorbed enzyme usually unaffected. Nearly full actv is retained.
n Support materials for enzyme adsorption :
Inorganic materials
alumina, silica, porous glass, ceramics,
clay, bentonite
organic materials
cellulose, starch, activated carbon, amberlite, sephadex, dowex
Entrapment
n Enzyme molecules are held/entrapped within the appropriate fibers or gels
n Matrix entrapment & membrane entrapment
n Matrices used :
Polymeric materials solid matrices
- Ca-alginate - activated carbon
- agar - porous ceramic
- K-carrageenin - diatomaceous earth
- Polyacrylamide
- Collagen
n The matrix can be a particle, a membrane or a fiber
n Entrapment may or may not necessarily be accomplished via covalent bonding existing between the enzyme entities (molecules) and the carrier matrix.
n non covalent bonding in entrapment can be considered as putting the enzyme in a molecular cage just like a caged bird.
n In a situation when the covalent bonding is needed, the enzyme molecules required to be treated with synthetic reagents e.g., acryloyl chloride, cellulose acetate etc.
n Entrapment method using polymer matrix (non covalent bonding)
1)Enzyme solution mixed with polymer solution
2)Polymerization occur
Entrapment when covalent bonding needed
1) the enzymes surface lysine residues may be derivatized by reaction with acryloyl chloride to give the acryloyl amides
2) Acryloyl amides are then co-polymerized and cross-linked with acrylamide and bisacrylamide to form a gel containing enzyme
3) Gel containing enzyme may be used to form a small bead or a film on a solid support
Encapsulation
n Encapsulation or microencapsulation or membrane confinement is another effective approach of enzyme immobilization
n A special form of membrane entrapment
n A droplet of Enzyme are entrapped in small capsules (diameter up to 300µm)
n The capsules surrounded by spherical membrane
n The membrane have pores permitting small substrate & product molecules to enter and leave the capsules
n However the pores are too small for enzyme & other large molecules to penetrate
n 2 type of membrane can be made:
a) permanent polymeric membrane
b) nonpermanent microcapsules
Important note : This is individual assignment and must be handwritten.