An Overview of Bacteriocins-Classification, Mode of action, Assays for detection and Role in Food Preservation.

1. Presentation by:
Kumuda J.

2.  Introduction
 Classification
 Mode of Action
 Isolation of Bacteriocins
 Assays for Detection of Bacteriocins
 Role in Food Preservation
 Advantages
 Applications

3.  Definition: Bacteriocins are ribosomally-synthesised toxic proteins
produced by bacterial strains which are not lethal to the producing
strain.
 Bacteriocins are the secondary metabolites synthesized by bacterial
strains during their stationary phase of growth.
 In 1925, the first bacteriocin, called Colicin was originally
identified as an antimicrobial protein produced by E.coli.

4.  India has various traditional food patterns varying from Northern
cuisine involving Roti, pickled fruits and vegetables to the Southern
Cuisine which is best known for spicy-hot blends, fresh pickles,
coconut milk and so on.
Fig. 01: Northern Cuisine Fig. 02: Southern Cuisine

5. Class I Class II
Class III Class IV
Bacteriocins

6.  Class I - the lantibiotics
 Class II - the small heat stable non lantibiotics/unmodified peptides
 Class III - large heat labile proteins
 Class IV - complex peptides carrying lipid or carbohydrate
moieties.
 The classification scheme for gram negative bacteria includes
modified proteins, non-lantibiotic heat stable bacteriocins, colicins
and microcins.
 Colicins and Microcins are compounds produced by bacteria
belonging to the family Enterobacteriaceae and distinguished based
on their size.

7.  Most of the bacteriocins destroy the energy potential of sensitive
cells, by forming membrane channels or pores. The best described
mechanism is pore formation.
Fig. 03: Mechanism of Pore Formation

8. Fig. 04: Mode of Action

9. Collect the MILK PRODUCTS
Make the appropriate dilutions
Incubate aerobically on de Mann Rogosa
Sharpe (MRS) agar
Isolate the bacteriocins producing bacteria
using pour plate technique
transfer colonies to the MRS broth, obtain the supernatant by
centrifugation
Obtain the precipitates containing bacteriocins
Fig. 05: Milk products

10. Dilute the APPAM BATTER with saline and plate on MRS agar
Incubate an-aerobically and obtain the colonies
Transfer to MRS broth
Obtain the supernatant by centrifugation
Sterilize by passing through filter membrane
Bacteriocins
Fig. 06: Appam batter

12.  Bacteriocins can diffuse in solid or semisolid culture media. Making
use of this fact, scientist conducted the experiment on detection of
bacteriocins using agar in 1970.
 Scientists utilized the ELISA for detection of the bacteriocins. They
used affinity-purified anti-nisin immunoglobulin for the binding of
nisin and anti-nisin peroxidase as the enzyme to be linked with the
substrate. The activity of bound enzyme was determined which
implied the amount of bacteriocins.

13.  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 the present, in the form of protective cultures
or their metabolites i.e. enzymes and bacteriocins.
 As there is an increase in demand for natural, minimal processed,
micro-biologically safe products, bacteriocins provide the
consumers with high health benefit.

14.  The bacteriocins from food grade Lactic Acid Bacteria (LAB)
qualify as an ideal food bio preservative primarily because:
i. It is proven non-toxic to humans.
i. Does not alter the nutritional properties of the food product.
ii. Effective at low concentration.
i. Active under refrigerated storage.
Fig. 07: Lactic Acid Bacteria

15. Bacteriocin Pathogenic
bacteria
Food system
Nisin Clostridium
botulinum,
Listeria
monocytogens
Cheese,
Camembert,
Ricotta cheese,
Manchego cheese
Pediocin ACH Listeria
monocytogens,
S.aureus, E. coli-
0157:H7
Milk and Cheddar
cheese
Enterocin AS-48
Enterocin AB,
Enterocin A,
Pediocin ACH
Listeria
monocytogens
Meat
Enterocin AS-48 B. cereus Rice, vegetables
Table 01: Various bacteriocins in food systems

16.  Advantages:
i. Safer preservatives than chemicals.
i. More accurate efficacy.
i. Good acceptance from consumers.
i. To overcome various drawbacks such as toxicity of chemicals
and nutritional alteration of food.

17.  Applications:
• Inhibition of pathogenic bacteria.
• Natural preservatives in food industries.
• Agricultural applications – in disease control.
• Pharmaceutical applications.
a. Lantibiotics – treat inflammation, allergies, skin infections,
peptic ulcers, etc.
b. Colicins – treat Haemorrhagic colitis and haemolytic uremic
syndrome.
c. Microcins – treat Salmonellosis.