3.5.4 The Lactobacillus Bacteriocins Sakacin A and Plantaricin . . . . . . 34
3.5.5 Class IIB Bacteriocins . . . . . . . . . . . . . . . . . . . . . . . . . . 35
4
Immunity and Resistance Towards Bacteriocins . . . . . . . . . . . 36
5
Biosynthesis of Bacteriocins Produced by Lactic Acid Bacteria . . . 38
5.1 Response Regulation . . . . . . . . . . . . . . . . . . . . . . . . . . . 38
5.2 Post-Translational Modifications . . . . . . . . . . . . . . . . . . . . 40
5.3 Secretion and Proteolytic Activation of Bacteriocin Precursors . . . 42
5.3.1 ATP-Dependent Translocation and Processing . . . . . . . . . . . . 42
5.3.2 Accessory Proteins of the Class II Non-Lantibiotic Bacteriocins . . . 44
5.3.3 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45
6
Role of the Leader Peptide . . . . . . . . . . . . . . . . . . . . . . . . 45
7
Conceptual Model for Bacteriocin Maturation . . . . . . . . . . . . 47
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50
1
Lactic Acid Bacteria and Their Bacteriocins
1.1
Lactic Acid Bacteria
Lactic acid bacteria are Gram-positive, catalase-negative, oxidase negative,
non-sporulating microaerophilic bacteria whose main fermentation product
from carbohydrates is lactate. The lactic acid bacteria comprise both cocci (e.g.
Lactococcus, Leuconostoc, Oenococcus, Pediococcus, Tetragenococcus, Streptococcus, Enterococcus) and rods (Lactobacillus, Carnobacterium, Bifidobacterium). Many of these lactic acid bacteria are generally recognized for their
contribution to flavor and aroma development and to spoilage retardation [1].
Therefore, the traditional use of these microorganisms in the fermentation of
foods and beverages has resulted in their application in many starter cultures
currently involved in the fermentation of a wide variety of agricultural raw
materials such as milk, meat, fruit, vegetables, cereals, etc. [2–7]. The lactic acid
bacterial strains present in these starter cultures contribute to the organoleptic
properties and the preservation of the fermented products by in situ production of antimicrobial substances such as lactic acid and acetic acid, hydrogen
peroxide, bacteriocins, etc. [8–11]. Because of the general tendency to decrease
the use of chemical additives, such natural inhibitors could replace the use of
chemical preservatives such as sulfur dioxide, benzoic acid, sorbic acid, nitrate,
nitrite, etc. [12]. For this reason, bacteriocins produced by lactic acid bacteria
may be very promising as biological food preservatives in future food preservation [13]. Furthermore, certain lactic acid bacteria, especially some lactobacilli and bifidobacteria, are believed to play a beneficial role in the gastro22
E. Sablon et al.
3.5.5 Class IIB Bacteriocins . . . . . . . . . . . . . . . . . . . . . . . . . . 35
4
Immunity and Resistance Towards Bacteriocins . . . . . . . . . . . 36
5
Biosynthesis of Bacteriocins Produced by Lactic Acid Bacteria . . . 38
5.1 Response Regulation . . . . . . . . . . . . . . . . . . . . . . . . . . . 38
5.2 Post-Translational Modifications . . . . . . . . . . . . . . . . . . . . 40
5.3 Secretion and Proteolytic Activation of Bacteriocin Precursors . . . 42
5.3.1 ATP-Dependent Translocation and Processing . . . . . . . . . . . . 42
5.3.2 Accessory Proteins of the Class II Non-Lantibiotic Bacteriocins . . . 44
5.3.3 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45
6
Role of the Leader Peptide . . . . . . . . . . . . . . . . . . . . . . . . 45
7
Conceptual Model for Bacteriocin Maturation . . . . . . . . . . . . 47
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50
1
Lactic Acid Bacteria and Their Bacteriocins
1.1
Lactic Acid Bacteria
Lactic acid bacteria are Gram-positive, catalase-negative, oxidase negative,
non-sporulating microaerophilic bacteria whose main fermentation product
from carbohydrates is lactate. The lactic acid bacteria comprise both cocci (e.g.
Lactococcus, Leuconostoc, Oenococcus, Pediococcus, Tetragenococcus, Streptococcus, Enterococcus) and rods (Lactobacillus, Carnobacterium, Bifidobacterium). Many of these lactic acid bacteria are generally recognized for their
contribution to flavor and aroma development and to spoilage retardation [1].
Therefore, the traditional use of these microorganisms in the fermentation of
foods and beverages has resulted in their application in many starter cultures
currently involved in the fermentation of a wide variety of agricultural raw
materials such as milk, meat, fruit, vegetables, cereals, etc. [2–7]. The lactic acid
bacterial strains present in these starter cultures contribute to the organoleptic
properties and the preservation of the fermented products by in situ production of antimicrobial substances such as lactic acid and acetic acid, hydrogen
peroxide, bacteriocins, etc. [8–11]. Because of the general tendency to decrease
the use of chemical additives, such natural inhibitors could replace the use of
chemical preservatives such as sulfur dioxide, benzoic acid, sorbic acid, nitrate,
nitrite, etc. [12]. For this reason, bacteriocins produced by lactic acid bacteria
may be very promising as biological food preservatives in future food preservation [13]. Furthermore, certain lactic acid bacteria, especially some lactobacilli and bifidobacteria, are believed to play a beneficial role in the gastro22
E. Sablon et al.