-Introduction -About bacteriocins -Classification of bacteriocins -Role in food preservation -How to add bacteriocins in foods -Advantages and disadvantages -Conclusion.

1. Role of bacteriocins in food safety
-Samyuktha Magesh

2. Contents
• Introduction
• About bacteriocins
• Classification of bacteriocins
• Role in food preservation
• How to add bacteriocins in foods
• Advantages and disadvantages
• Conclusion.

3. ❏ Definition:Bacteriocins are ribosomally-synthesized toxic proteins
produced by bacterial strains which can kill or inhibit bacterial strains
closely related or non related to the produced bacteria,but will not harm
the bacteria themselves by specific immunity proteins.
❏ Antimicrobial peptides(AMPs)or proteins produced by bacteria are
categorised as bacteriocins.
❏ Bacteriocins are the secondary metabolites synthesised by bacterial
strains during their stationary phase of growth.
❏ In 1925,the first bacteriocin,called colic in was originally identified as an
anti-microbial protein produced by E.coli.
Introduction

4. About bacteriocins
✔Bacteriocins are proteinaceous or peptidic toxins produced by bacteria
to inhibit the growth of similar or closely related bacterial strain. They
are similar to yeast and paramecium killing factors, and are structurally,
functionally, and ecologically diverse.
✔Bacteriocins of lactic acid bacteria play a defining role in the
preservation & microbial safety of foods
✔Bacteriocins may have broad or narrow spectrum of activity
✔Bacteriocins with broad spectrum of activity are of great importance
in food safety while bacteriocins with narrow spectrum of activity may be
used for specific use

5. Classification of bacteriocins
BACTERIOCINS FROM GRAM NEGATIVE BACTERIA
❖ Colicins
❖ Microcins
BACTERIOCINS FROM GRAM POSITIVE BACTERIA
❖ Class I(modified peptides)
❖ Class II(unmodified peptides),and
❖ Class III(large proteins,heat unstable)
❖ Class IV

6. BACTERIOCINS FROM GRAM NEGATIVE BACTERIA
❖ Microcins
Microcins are very small bacteriocins, composed of relatively few amino acids. For this
reason, they are distinct from their larger protein cousins. The classic example is
microcin V, of Escherichia coli. Subtilosin A is another bacteriocin from Bacillus
subtilis.
❖ Colicins
A colicin is a type of bacteriocin produced by and toxic to some strains of Escherichia coli.
Colicins are released into the environment to reduce competition from other bacterial
strains.They often consist of a receptor binding domain, a translocation domain and a
cytotoxic domain. Combinations of these domains between different CLBs occur frequently
in nature and can be created in the laboratory.

7. Class I bacteriocins
The class I bacteriocins are small peptide inhibitors and
include nisin and other lantibiotics.
Class II bacteriocins
The class II bacteriocins are small heat-stable proteins.
Class III Bacteriocins
Class III bacteriocins are large, heat-labile protein
bacteriocins
Class IV bacteriocins
Class IV bacteriocins are defined as complex
bacteriocins containing lipid or carbohydrate moieties.
BACTERIOCINS FROM GRAM POSITIVE BACTERIA

8. Role in food preservation
❖ There is a continuous raise of awareness in the public regarding the amount of
chemical intake by their body as food preservatives.
❖ In view of the above problem, bio- preservatives are in very high commercial
demand at present, in the protective cultures of their metabolites i.e.
enzymes and bacteriocins.
❖ As there is an increase in demand for natural,minimal
processed,microbiologically safe products,bacteriocins provide the consumers
with high health benefit.

9. Lactic acid bacteria
The bacteriocins from food grade
Lactic acid bacteria (LAB) qualify as an
ideal food bio preservative primarily
because;
1) it is proven non -toxic to humans
2) Does not alter the nutritional
properties of the food product.
3) Effect at low concentration
4) Active under refrigerated storage.

10. Various bacteriocins in food systems

11. How to add bacteriocins in foods
Traditional methods for incorporation of bacteriocin preparation in foods

12. Newly emerged techniques for incorporation of bacteriocin preparation preparations
in foods

13. ➢ " antimicrobial packaging (amp) is the packaging system that is able to kill or
inhibit spoilage and pathogenic organism that are contaminating foods "
➢ Antimicrobial packaging film prevents microbial growth on food surface by
direct contact of the package with the surface of foods
➢ The classical protective function of Packaging is supported by the action of
relevant bacteriocins
1) Antimicrobial packaging(AMP)

14. ➔ Delivery systems used for immobilisation of
bacteriocins
Silica gel,gelatine,collagen casings,cast proteins
films,polymer film coatings,calcium alginate,methyl
cellulose films,corn zein,wheat gluten films
➢ Nisin is a highly surface active molecule that can
bind to different compounds,such as fatty acids of
phospholipids
➢ It’s a suitable feature for adsorption to solid
surfaces and killing of bacterial cells that
subsequently adhere

15. 2)Microencapsulation
● “It is a technology whereby the target molecule is packaged in
miniature,sealed capsules to protect it from external factors and deliver
in the targeted site under specific conditions”.
● Minimises bacteriocin resistance development and helps to achieve
controlled release controlled release of bacteriocins

16. ➔ Food grade polymers like
alginate,chitosan,carboxymethyl
cellulose,carrageenan,gelatin and
pectin are mostly applied,using
various microencapsulation
technologies

17. ● Nanoliposomes provide more surface
area
● Improve the distribution in the food
system along with the bioavailability of
the encapsulated bacteriocins
● Added directly to the food items
3) Nanoencapsulation
➢ Bacteriocins are very small molecules to be efficiently retained in porous
micro capsules which may lead to leakage or inefficient delivery at the target
site.
Hence many times primarily encapsulation of bacteriocins in nanosized liposomes is
popularly followed.

18. 4)Bacteriocins as a part of hurdle technology
“Use of hurdles of differing levels of
intensity to bring microbial growth
under control”.
Lactic acid bacteria have long been used as components of hurdle
technologies due to their ability to rapidly drop the pH in fermented
foods and competitively inhibit the growth of other microorganism,
which, in part, is due to their production of broad spectrum bacteriocins.

20. Advantages
Safer preservatives than
chemicals.
More accurate efficacy
Good acceptance from
consumers
To overcome various
drawbacks such as toxicity
of chemicals and nutritional
alteration of food
Disadvantages
Generally bacteriocins are not
useful as food preservatives
because they are expensive to
make, are broken down in food
products.
They harm some proteins in
food, and they target too
narrow a range of microbes.

21. Conclusions
➔ Bacteriocins of LAB and bacteriocin-producing cultures are
attractive options in food safety & biopreservation .
➔ Further research into the synergistic reactions of these
compounds and other natural preservatives,in combination with
advanced technologies could result in replacement of chemical
preservatives.
➔ Application of bacteriocins could allow less severe processing
treatments,while still maintaining adequate microbiological
safety and quality in foods