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Bacteriocins from lactic acid
bacteria and their potential
in the preservation of fruit
products
1
Muhammad Iqbal
Ph.D Scholar (Botany)
2nd Semester (13-arid-3283)
Contents
Introduction
Importance of studying LAB bacteriocins as an alternative in
fruit product preservation
Biotechnological approaches for the use of bacteriocins in
fruit products
LAB bacteriocins with potential in the preservation of fruit
products
Conclusion
2
Introduction
Bacteriocins are ribosomally synthesized and extracellularly release
antimicrobial peptides produced by bacteria that vary in structure,
biochemical properties, mode of action and spectrum of activity [1–
3]
The bacteriocins produced by lactic acid bacteria (LAB) are more
thoroughly characterized on account of their “food grade quality”
and industrial importance
These peptides are mainly active against bacteria and can inhibit
several food-borne spoilage and pathogenic microorganisms
3
Conti….
The interest in the use of bacteriocins as an alternative food
preservation method has increased with consumer demand for
fresh-tasting and better-preserved chemical free food products
Bacteriocins generally do not cause changes in food products and
can be used as an additional gradient in food processing, reducing
the intensity of traditional preservation methods, such as heat [1]
In this way, the increase in the consumption of fruit products [8]
and consumer demand for food products that maintain their
natural characteristics [9] make bacteriocins as great candidates to
be used for the preservation of fruit products.
4
Conti….
The use of bacteriocins as food additives is widespread, however,
little is known about its use in fruit products, especially in
minimally processed fruits [4,5,10]
In the few last years, fruit products have been increasingly
associated with food-borne pathogens and spoilage
microorganisms [11–16].
Several LAB bacteriocins have been characterized and their
potential as natural food preservatives has been demonstrated [4–
7]
5
Importance of studying LAB bacteriocins as an
alternative in fruit product preservation
Bacteriocins could be used in this kind of products by using pure
bacteriocins as food additives or by the use of bacteriocinogenic
strains as starter cultures, protective cultures or co-cultures
Bacteriocins can ensure microbiological safety and also
contribute to maintain the nutritional properties of fruits
Results have previously shown that nisin, apart from its
antibacterial activity, also contributes to preserve the vitamin C
content of minimally processed mangoes and fruit juices [48,50]
6
7
8
Biotechnological approaches for the use of
bacteriocins in fruit products
Some studies have shown the potential of semi or purified forms of
the bacteriocins to preserve fruit juices and pulps by direct addition
[6,7,10,18,50]. These products are generally thermally-processed,
therefore, it is important that the bacteriocins are heat-stable
One approach to use bacteriocins in the conservation of minimally
processed fruits is by incorporating these peptides in the packaging
material [48]
This is known as active packaging which, besides protecting the
product from external environment, inhibits microbial growth,
minimizing direct addition of preservatives
9
Conti.....
Bacteriocin-incorporated films avoid the risks of negative
interaction with the food components and can provide longer
preservation compared with the conventional addition directly
into the food [51].
This is a promising technology, as the majority of solid or
semisolid foods present high microbial growth on their surface
[56]
However, the information available on the use of active
packaging containing bacteriocins for the preservation of
minimally processed fruits is still limited [48].
10
Conti.....
Edible coatings added with bacteriocins could also be a great
alternative to preserve minimally processed fruits
Thin layers of biopolymers (carbohydrate, lipid or protein)
applied directly on the surface of whole or minimally processed
fruit,
prevent water loss
reduce respiration rates [57]
Also used as carriers of bioactive ingredients, such as
bacteriocins, to prolong shelf-life [20]
11
12
Figure 1. Bacteriocins: Mode of action
13Figure 1. Bacteriocins: mode of action (Cotter et al., 2005) modified
after.
LAB bacteriocins with potential in the
preservation of fruit products
14
Many bacteriocins have been used in the preservation of fruit
products such as;
Nisin
Enterocin AS-48
Bovicin HC5
Enterocin 416K1
Bificin C6165
Pediocin
Nisin
Nisin is the most studied and best characterized bacteriocin for
the preservation of fruit products. It is a bacteriocin produced by
strains of Lactococcus lactis subspecies lactic and consists of a
34-residue peptide
Nisin has been approved to be used in foods since 1988 by the US
Food and Drug Agency (FDA) [2]
It has been used in processed cheeses, dairy products and canned
foods [81], but its approval in fruit products is limited to certain
countries
This bacteriocin is thermostable and its activity is increased at
acidic pH [82]
15
Conti.....
Nisin is active against S. aureus, L. monocytogenes, Clostridium
and Bacillus spores and even inhibits some Gram-negative
bacteria [1,48,83]
This bacteriocin inhibited vegetative growth and spore outgrowth
16
17
Bovicin HC5
Bovicin HC5 is a bacteriocin produced by strains of
Streptococcus bovis HC5, a rapidly growing Gram positive
bacterium
It exhibits stability at high temperatures and acidic pH and has
inhibitory activity against several strains of food-borne pathogens
and spoilage microorganisms, including L. monocytogenes,
Clostridium tyrobutyricum, B. cereus and B. thuringiensis
It also inhibits strains of LAB, such as Streptococcus,
Lactococcus, Enterococcus and Lactobacillus [6,7,18,92,98].
This bacteriocin showed effectiveness in preserving fruit juices
and pulps
Enterocin AS-48
Enterocin AS-48 is a 70-residue cyclic peptide produced byEnterococcus faecalis subsp. liquefaciens S-48, and consists of aglobular arrangement
Enterocin AS-48 shows a broad antimicrobial spectrum againstboth Gram-positive and Gram-negative bacteria and is also stableat high temperatures and active at acidic pH [99]
Spoilage and pathogenic microorganisms related to fruit products,such as S. aureus, L. monocytogenes, B. cereus andAlicyclobacillus sp., were efficiently inhibited by enterocin AS-48 [4,5,59,103–106]
Enterocin AS-48 was tested in canned pineapple juice, apple ciderand several fruit juices
19
Enterocin 416K1
Enterocin 416K1 is a 5 kDa bacteriocin produced by strains of
Enterococcus casseliflavus 416K1 isolated from Italian sausages
This bacteriocin is stable upon heating at 90 C for 120 min and
storage at 4 C for 6 months, and has demonstrated strong
antibacterial activity [110]
Enterocin 416K1, alone or in combination, could be a feasible
solution to extend the shelf-life and to obtain the microbiological
safety of ready-to-eat vegetable and fruits [19]
20
Bificin C6165
Bificin C6165 is produced by strains of Bifidobacterium animalis
subsp. animalis 6165 and has shown higher activity at acidic pH
and elevated temperatures
Bificin C6165 showed antimicrobial activity against several
strains of A. acidoterrestris, LAB strains and Gram positive
bacteria including S. aureus and Enterococcus faecium [58]
Bificin could also be tested to be used in edible coating or in the
matrix of plastic films used for packaging minimally processed
fruits
21
Pediocin
The antibacterial peptide pediocin has 44 amino acid residues
and, as with nisin, is commercially available to be used in food
preservation [2,113]
This bacteriocin has stability over a wide pH range (3–9) and
heat-processing temperatures (65–121 C) [113]
Pediocin exhibits antibacterial activity against a wide spectrum of
food-borne pathogens and food spoilage Gram-positive bacteria
[114]
This bacteriocin has been extensively studied for its use in food
preservation, mainly for foods of animal origin [114–116]
Pediocin could also be used to produce antimicrobial films to
package minimally processed fruits 22
Other Bacteriocins
Some other examples of bacteriocins with these characteristics
are;
Pentocin
TV35b
Enterocin A5-11
Bacteriocin EF2019
Bacteriocins produced by strains of Pediococcus and Lactococcus
from the human intestine
23
24
Conclusion
Considering the fact that some food-borne pathogenic and spoilage
microorganisms are very dangerous, the purification and
characterization of novel bacteriocins are of great relevance in
order to develop novel products and applications
The use of purified or semi purified preparations of bacteriocins as
food preservatives have legal implications
In order to be approved for commercial and industrial applications,
studies must be performed to provide detailed safety information
supported by toxicological data
Additionally, proof of efficacy in foods, description of
manufacturing process, as well as the safety levels should be
investigated25
Reference
Ana Andréa Teixeira Barbosa, Hilário Cuquetto Mantovani &
Sona Jain (2017): Bacteriocins from lactic acid bacteria and their
potential in the preservation of fruit products, Critical Reviews in
Biotechnology,
DOI: 10.1080/07388551.2016.1262323
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4033612/
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