ReviewFood biopreservation: promising strategies using bacteriocins, bacteriophages and endolysins
Introduction
Food borne diseases are among the most serious and costly public health concerns worldwide, being a major cause of morbidity. In spite of modern technologies, good manufacturing practices, quality control and hygiene and safety concepts such as risk assessment and HACCP, the reported numbers of food-borne illnesses and intoxications still increased over the past decade. The most common food-borne infections in the European Union (EU) are caused by bacteria, namely Campylobacter, Salmonella and Listeria, and viruses. They are reported to affect over 380,000 EU citizens each year (EFSA, 2009).
Food market globalization, the introduction of novel foods, new manufacturing processes and the growing demand for minimally processed, fresh-cut and ready-to-eat products may require a longer and more complex food chain, increasing the risk of microbiological contamination. Thus, novel and complementary food preservation technologies that comply with these demands from “farm to fork” are continuously seeked. Among alternative food preservation technologies, particular attention has been paid to biopreservation to extent the shelf-life and to enhance the hygienic quality, minimizing the impact on the nutritional and organoleptic properties of perishable food products. Biopreservation rationally exploits the antimicrobial potential of naturally occurring (micro-) organisms in food and/or their metabolites with a long history of safe use. Bacteriocins, bacteriophages and bacteriophage-encoded enzymes fall in this concept. This review will summarize basic knowledge and current applications of these natural antimicrobials along the food chain. Based on this state-of-the-art, future trends and areas of research that deserve more attention will be discussed.
Section snippets
Bacteriocins: structure and mode of action
Bacteriocins are bacterial ribosomally synthesised peptides or proteins with antimicrobial activity. They were primarily described in Escherichia coli (colicins). Most of the colicins are relatively large proteins (up to 80 kDa) that kill very closely related bacteria upon binding to the inner membrane or other cytosolic targets (Cascales et al., 2007). Nowadays, the term bacteriocin is mostly used to describe the small, heat-stable cationic peptides synthesised by Gram positive bacteria,
Current bacteriocin food applications
The traditional role of LAB on food and feed fermentations is the main load-bearing pillar on which the use of bacteriocins in biopreservation relies. LAB and their bacteriocins have been consumed unintentionally for ages, laying down a long history of safe use. Their spectrum of inhibition, bactericidal mode of action, relative tolerance to technologically relevant conditions (pH, NaCl, heat treatments) and the lack of toxicity towards eukaryotic cells further support their role as
Bacteriophages and their antibacterial life cycle
Bacteriophages or phages are the most abundant microorganisms on Earth (1031 particles) and widely spread including foods of various origins (Brüssow & Kutter, 2005). Bacteriophages are viruses that specifically infect and multiply in bacteria. Thus, they are harmless to humans, animals, and plants. The phages are classified into 13 families based on their shape, size, type of nucleic acid and presence/absence of envelope or lipids in their structure. Most of them belong to the Caudovirales
Current bacteriophage-based food applications
The concept of combating pathogens in food using phages is recent but several applications along the food chain have already been approached (Fig. 1) and several companies have already begun investing in phage technology (García, Martínez, Obeso, & Rodríguez, 2008). Bacteriophages are suitable i) to prevent or reduce colonization and diseases in livestock (phage therapy), ii) to decontaminate carcasses and other raw products, such as fresh fruit and vegetables, and to disinfect equipment and
Endolysins: structure and mode of action
Bacteriophages have developed two basic ways to release the new virions from the infected bacterial cells. In filamentous bacteriophages the progeny is continuously extruded from bacteria cells without killing, whereas non-filamentous bacteriophages destroy the cell wall of the host bacterium by phage-encoded lytic enzymes. Small RNA and DNA phages encode specific proteins that interfere with host enzymes responsible for peptidoglycan biosynthesis. In large DNA phages, endolysins (also termed
Endolysins in food applications
Most of work that supports the role of endolysins as powerful antimicrobials has been focused on prophylaxis and treatment of bacterial infections in animal models. In regard to food biopreservation, research is still at its infancy. However, the number of endolysins active against numerous zoonotic and food-borne pathogens which are being isolated and characterized is increasing exponentially and future applications are foreseen. Worth mentioning is the fact that to date no resistance to
Topics for the future
Despite of the vast knowledge generated on bacteriocin and bacteriophage biology and the increasing attention paid to endolysins, there are still several basic and applied issues that deserve further attention to fully exploit their antimicrobial potential in food safety (Table 2).
Special needs in basic research may be grouped in three main fields: i) resistant mechanisms, ii) new and/or enhanced antimicrobials, and iii) safety concerns which may emerge by the use of these biopreservatives.
Acknowledgements
The DairySafe group at IPLA-CSIC is financially supported by grants from the Spanish Government BIO2007-65061 and AGL2009-13144-C02-01 and the regional research program FICYT IB08-052.
References (68)
- et al.
Optimization of enterocin AS-48 production on a whey-based substrate
International Dairy Journal
(2008) - et al.
Bacteriophage P100 for control of Listeria monocytogenes in foods: genome sequence, bioinformatic analyses, oral toxicity study, and application
Regulatory Toxicology and Pharmacology
(2005) - et al.
Nisin biotechnological production and application: a review
Trends in Food Science and Technology
(2009) - et al.
New preservation technologies: possibilities and limitations
International Dairy Journal
(2004) - et al.
The non-enzymatic microbicidal activity of lysozymes
FEBS Letters
(1999) Bacteriophage lysins as effective antibacterials
Current Opinion in Microbiology
(2008)- et al.
Bacteriocin-based strategies for food biopreservation
International Journal of Food Microbiology
(2007) - et al.
Biocontrol of Staphylococcus aureus in curd manufacturing processes using bacteriophages
International Dairy Journal
(2007) - et al.
Prevalence of bacteriophages infecting Staphylococcus aureus in dairy samples and their potential as biocontrol agents
Journal of Dairy Science
(2009) Bacteriophages: an appraisal of their role in the treatment of bacterial infections
International Journal of Antimicrobial Agents
(2007)