Nano and microencapsulation of bacteriocins for food applications: A review

International audienceThe increasing demand for prolonging food shelf life and inhibiting food spoilage and pathogenic microorganismslead to development of novel biopreservatives and conservation methods. Antimicrobial peptides derivedfrom microorganisms like bacteriocins are considered as a major alternative to the application of chemicalpreservatives in food products. Direct addition of purified antimicrobial peptides into food matrix results inreduced antibacterial activity due to the interaction of peptides with food components. Nano- or microencapsulationprocess can protect biopreservatives against many adverse conditions and controlled release of theagents efficiently prevent microbial contamination and food spoilage. This review focuses on the most frequentlyused chemical, physical and mechanical encapsulation methods for various antimicrobial bacteriocins includingliposome entrapment, coacervation, emulsification, spray-drying, and vibrating technology. The most recentapplications of nano- or microencapsulated antimicrobial bacteriocins with emphasis on nisin and pediocin invarious food products like dairy, meat products and fruit juice have been discussed

Nisin

International audienceNisin is a 34-amino acid peptide known as a bacteriocin. It belongs to class-Ia bacteriocins known as lantibiotics. It is the most characterized and commercially used antimicrobial peptide. It was commercialized in the 1950s for the prevention of late blowing in cheese by Clostridium. Nisin is heat-stable and a cationic, low-molecular-weight peptide produced by the bacterial dairy starter Lactococcus lactis subsp. lactis. The growth of a wide spectrum of Gram-positive bacteria, including the pathogens Listeria and Staphylococcus aureus, and spore-forming bacteria such as Bacillus and Clostridium can be prevented by nisin. Subjects addressed in the chapter include nisin structure and physicochemical properties, antimicrobial spectrum, factors affecting the antimicrobial activity (food composition, temperature, pH, proteolytic enzymes, food processes, other preservatives, bacterial load), application as a preservative to dairy products, meat products, seafood, fruits and vegetables, beverages, and other food products, use of nisin in food packaging systems, and regulatory status

Properties of lysozyme/sodium alginate complexes for the development of antimicrobial films

Complexation study of lysozyme (0.714g/L) by sodium alginate at pH7 showed that aggregates formation was a two-phase process. The first phase (from 0 to 0.1g/L sodium alginate) corresponded to the combination of individual complexes to form aggregates which caused an increase of turbidity and average size and a rapid sedimentation. Charge neutralization estimated by ζ-potential measurements occurred at 0.1g/L sodium alginate concentration. The second phase (from 0.1 to 4g/L of sodium alginate) was characterized by the formation of aggregates having a less dense structure with higher average size despite the drop in turbidity and the high dispersion in the medium. Lysozyme enzymatic activity decreased upon complexation with sodium alginate but was fully recovered after calcium chloride addition. In order to check whether lysozyme reversible inactivation was only due to substrate diffusion limitation or to conformational changes upon complexation, fluorescence and UV–Vis absorption measurements were performed. Moreover, lysozyme/sodium alginate complexes were used to manufacture an edible antimicrobial film to target lysozyme sensitive microorganisms

Microencapsulation of Natural Food Antimicrobials: Methods and Applications

The global demand for safe and healthy food with minimal synthetic preservatives is continuously increasing. Some natural food antimicrobials with strong antimicrobial activity and low toxicity have been considered as alternatives for current commercial food preservatives. Nonetheless, these natural food antimicrobials are hardly applied directly to food products due to issues such as food flavor or bioavailability. Recent advances in microencapsulation technology have the potential to provide stable systems for these natural antibacterials, which can then be used directly in food matrices. In this review, we focus on the application of encapsulated natural antimicrobial agents, such as essential oils, plant extracts, bacteriocins, etc., as potential food preservatives to extend the shelf-life of food products. The advantages and drawbacks of the mainly used encapsulation methods, such as molecular inclusion, spray drying, coacervation, emulsification, supercritical antisolvent precipitation and liposome and alginate microbeads, are discussed. Meanwhile, the main current applications of encapsulated antimicrobials in various food products, such as meat, dairy and cereal products for controlling microbial growth, are presented

Low methoxyl pectin/sodium caseinate interactions and composite film formation at neutral pH

The behavior of mixed negatively charged sodium caseinate (CAS) and low methoxyl pectin (LMP) at pH 7.0 was presented by phase diagram. The existence of interactions between CAS and LMP as a function of increasing protein concentration at neutral pH was studied by turbidity and zeta potential measurements. The observed significant increase of turbidity value for higher CAS/LMP ratios as well as the obtained zeta potential profile confirmed the formation of complexes at pH 7.0 at which the two macromolecules are negatively charged. Then, composite films were elaborated from CAS and LMP mixtures by increasing protein to polysaccharide ratio at neutral pH. The results revealed that the incorporation of protein to pectin-based films significantly increased the stiffness of films (Young’s modulus) and decreased their flexibility (p \\textless 0.05). Water content of composite films decreased significantly as the concentration of CAS increased (p \\textless 0.05) and reached its lowest value for CAS/LMP ratios of 2 and 5 (7.50 ± 0.10% and 7.63 ± 0.19%) compared to LMP film (19.82 ± 0.19%). The prepared films, having tunable properties by varying the ratio of CAS/LMP, seem to be adequate for the packaging of moist foods

Dorsal intradural spinal arteriovenous fistula associated with giant intradural spinal aneurysm, a case report

Abstract Arteriovenous fistula and spinal aneurysms like other vascular malformations can mimic radiculopathy and low back pain. Precise imaging work combined with a hybrid endovascular‐microsurgical approach is the key element for the best clinical outcome