Microbial enzymes have several advantages for food processing including producing specific products through single step reactions and allowing control over reactions. Common enzymes used include amylases, catalase, cellulases, invertase, lactase, lipases, and proteases. Recombinant DNA technology has improved enzyme efficiency by allowing production in bacterial sources. Immobilized enzymes can be recycled but may have reduced activity. Thermostable enzymes are advantageous for food processing as they allow increased production rates and reduced contamination risks. Methods to improve enzyme thermostability include gene cloning and computer modeling to modify amino acid sequences. Enzymes can also help treat food waste by breaking down polysaccharides, proteins, and other materials for conversion to valuable products like

1. Microbial Enzymes in Food
Processing

2. Advantages of using Enzymes
• Specific substrate-----specific product
Single step reaction
• Can avoid Production of metabolites
• Reaction can be controlled or enhanced
• Recombinant DNA Tech = Efficiency of enzyme
by immobilizing--recycling

4. Enzymes Used
1. a-Amylase, Glucoamylase, and Glucose
Isomerase
2. Catalase
3. Cellulase, Hemicellulase, and Pectinase
4. Invertase
5. Lactase
6. Lipases
7. Proteases

5. a-Amylase, Glucoamylase, and
Glucose Isomerase
• Starch----High fructose corn syrup
• Bread making- staling a-Amylase
Glucoamylase
Glucose Isomerase
Starch
Oligosaccharides
(containing three hexose
units or more, e.g., dextrins)
Glucose
Fructose

6. Enzyme production by Rec. DNA Tech.
• Sources = Yeast, mold , plant, mammalian
• Disadvantages = limited supply, costly
• Molds = grow slower, produce mycotoxins
• Bacterial source = convenient and cost-effective
• mRNA--- CDNA--- Plasmid--- bacteria--- production
• Renin(calf) and Cellulases(molds)

7. Immobilized Enzymes

8. Disadvantages of Immobilization
• Reduce activity of enzyme
• Substrate molecules may not be freely accesible
• Large substrates (e.g)
• Contamination of supporting material
• Supporting material must not be unsafe
• Commercially used immobilized enzymes (glucose
isomerase,b-galactosidase, and aminoacylase)

9. Thermostable Enzymes
• enzymes that can catalyze reactions above
60°C
Advantages
• The rate of an enzyme reaction doubles for
every 10°C increase in temperature
production rate can be increased
the amount of enzyme used can be reduced
the problems of microbial growth and
contamination can be reduced.

10. Thermostable Enzymes
• The stability of the 3D structure of an enzyme
is influenced by the ionic charges, hydrogen
bonding, and hydrophobic interaction among
the amino acids
• ion pairing, hydrogen bonding and increases in
internal hydrophobicity = the
thermostability of an enzyme

11. Thermostable Enzymes
Example:
• Tyrosinase from a thermolabile strain of Neurospora
species denatures in 4 min at 60°C
• thermostable strain of the same species it denatures in 70
min at 60°C.
• at position 96, tyrosinase has an aspargine (uncharged) in
the thermolabile strain
• aspartic acid (charged) in the thermostable strain.
• Thus, an extra ionic charge (on the surface) increases the
thermostability of this enzyme.

12. Increase Thermostability of Enzyme
• Rec. DNA Tech.----Two methods
1. Gene Cloning
2. Computer modeling (Bioinformatics)

13. 1-Determining the amino acid sequence of the
enzyme
2- 3D structure (by computer modeling) to
recognize the amino acids on the surface (or inside)
3- Changing one or more amino acids on the surface
to increase ionic or hydrogen bonding (site-specific
mutagenesis of base sequences of cDNA)

14. 4- Synthesized DNA
can be incorporated
in a vector
5- Introduced in a
desired microbial
strain for Expression
of the enzyme
6-Testing for its
thermostability

15. Enzymes in Food waste Treatment
• Solid and liquid waste
• Physical, chemical, and some biological methods
• Anaerobic digestion and production of SCPs
• Using enzymes to reduce wastes and convert the
wastes to value-added products
• availability of specific enzymes at low costs

16. Enzymes in Food waste Treatment
• Polysaccharidases (cellulase, pectinase,
hemicellulase, chitinase, and amylase),
• lactase
• Proteinases
Examples:
• Pectinase = separation of solids from the juice.
• The solids can be used as animal feed

17. Enzymes in Food waste Treatment
• Examples:
• Chitinases = depolymerize the shells of shellfish, and
the product used to produce SCPs.
• Amylases---to treat starch-containing wastewater---
glucose syrup for use in alcohol production by yeasts.
• Lactose in whey has been treated with lactase (b-
galactosidase)---glucose and galactose----used in
alcohol production by yeast or to produce bakers’
yeasts.
• Proteases---to treat wastewater from fish and meat-
processing operations----products are used as fish
food.