This document discusses bacteriocins, which are toxic proteins produced by bacterial strains that kill other bacteria but not the producing strain. It defines bacteriocins and explains they range in size from less than 10kD to greater than 10kD. Bacteriocins are classified based on their mode of production, killing mechanism, genetic material, and presence of modifications. Lactic acid bacteria like Lactococcus and Lactobacillus produce several bacteriocins. The document outlines methods for isolating and purifying bacteriocins from milk and describes their applications.

1. T . T HIR UMAGAL
M. S C B I OTECHNOLOGY
B ON S E C OUR S C OLLEGE F OR
W OMEN
T HANJ AVUR .
BACTERIOCINS FROM
LACTIC ACID BACTERIA

2. WHAT IS BACTERIOCINS?
 Bacteriocins are ribosomally synthesized toxic
proteins produced by bacterial strains which are
not lethal to the producing bacterial strain.
 These are small peptide molecules range from
 <10 KD _ >10KD.
Bacteriocins
Produced by
Bacteria
Archea

3. Why Bacteriocins are produced?
Required for bacterial
own defense mechanism
Bacterial growth
Suppress other
pathogenic growth

4. Based On Mode Of
Killing
Based On Mode Of
Production
Based On Chemical
Modification
Based On Genetic
Material
 Pore forming  Ribosomal  Post-
translational
modification
 Large plasmid
 Nuclease
activity
 Non-ribosomal  Abnormal
amino acid
incorporation
 Small plasmid
 Cell wall
degrading
 Post ribosomal  Sugar addition  Chromosomal
CLASSIFICATION OF BACTERIOCINS

5. Anti-microbial activity of bacteriocin

6. Hegg & Tagg Classification of Bacteriocins
CLASS I Lantibiotics
CLASS II Small Heat Stable Non-
Lantibiotics /Unmodified Peptide
CLASS III Large Heat Lable Proteins
CLASS IV Complex Peptides Carrying Lipid
Or Carbohydrate Moieties

7. Bacteriocins from lactic acid bacteria[LAB]
 Lactic acid bacteria are G+ve, low-GC, acid-tolerant,
generally non-sporing, either rod shaped or
spherical bacteria.
 Usually found in decomposing plants and milk
products, produce lactic acid as the major
metabolic end product of carbohydrate
fermentation.
 Proteinaceous substances [Bacteriocins] are
produced by several LAB strains and provide an
additional hurdle for spoilage and pathogenic
microorganisms.

8. LAB genera
producing
Bacteriocins
LactococcusLactobacillus

9. Properties of Bacteriocins from LAB
class Typical producing species properties Examples
I Lactobacillus lactis Contain unique amino acids like
lanthionine and
methyllanthionine
Nisin,
Lactosin,
Mersacidin
II a Leuconostoc gelidum Heat stable, non-modified,
cationic, hydrophobic peptides
contain a double-glycine leader
peptide
Pediocin,
Sakicin,
Leucocin
II b Enterococcus faecium Require synergy of two
complementary peptides
mostly cationic peptides
Lactococcin,
Plantaricin,
Enterocin
II c Lactobacillus acidophillus Affect membrane permeability
and cell wall formation
Acidocin,
Enterocin,
Neuterin
III Lactobacillus helveticus heat-labile, large molecular
mass peptides
Lyostaphin,
Enterolysin
Helveticin.

10. Production of Bacteriocin
Collect the milk products or appam batter
Make the appropriate dilutions
Incubate on de Mann Rogosan & Sharpe(MRS)
Agar
Aerobic incubation for milk products & Anaerobic
incubation for batter
Isolate the Bacteriocin producing colonies by pour
plate technique
Obtain supernatant by centrifugation

11. Transfer colonies to MRS Broth
Bacteriocin producing strain start to grow
Obtain supernatant by centrifugation
Obtain the precipitate containing bacteriocin.
Sterilize by filtration process
Purified bacteriocin were prepared.

12. Applications of bacteriocins

13. THANKYOU