Synergistic antibacterial effect of nisin, ethylenediaminetetraacetic acid, and sulfite on native microflora of fresh white shrimp during ice storage

Enterocin LD3 from Enterococcus hirae LD3 Inhibits the Growth of Salmonella enterica subsp. enterica serovar Typhimurium ATCC 13311 in Fruit Juice

In order to prevent the growth of pathogens in food, bacteriocins produced by various probiotic lactic acid bacteria have been recognized as potential substitutes of chemical preservatives. In this study, enterocin LD3 was purified from the cell-free supernatant of a food isolate, Enterococcus hirae LD3 using multistep chromatography. In the fruit juice, lethal concentration (LC50) of enterocin LD3 was found to be 260 µg/mL against Salmonella enterica subsp. enterica serovar Typhimurium ATCC 13311. The cells treated with enterocin LD3 were red colour indicating dead cells after propidium iodide staining, while untreated cells were found blue after staining with 4', 6-diamidino-2-phenylindole. The mechanism of cell killing was analyzed using infrared spectrum of cells treated with enterocin LD3 which was found altered in the range of 1,094.30 and 1,451.82 cm-1 corresponding to nucleic acids and phospholipids, respectively. The morphology of target cells were severely ruptured and lysed as observed under electron microscopy. Thus, the present study suggested that enterocin LD3 showed bactericidal activity against Salm. enterica subsp. enterica serovar Typhimurium ATCC 13311 and may be applied as a bio-preservative for the safety of fruit juices.

Evaluation of antibacterial properties of nisin peptide expressed in carrots

Nisin, derived from Lactococcus lactis, is a well-known natural food preservative. In the present study, the gene of nisin was transformed to carrot by Agrobacterium tumefaciens strain LBA4404 harboring the recombinant binary vector pBI121 containing neomycin phosphotransferase II (nptII) gene, peptide signal KDEL, and Kozak sequence. The integration of nisin and nptII transgenes into the plant genome was confirmed by polymerase chain reaction (PCR) and dot blot analysis. The gene expression was also performed by RT-PCR and Enzyme-Linked Immunosorbent Assay. The level of nisin expressed in one gram of transgenic plant ranged from 0.05 to 0.08 μg/ml. The stability of nisin varied in orange and peach juices depending on the temperature on the 70th day. The leaf protein extracted from the transgenic plant showed a significant preservative effect of nisin in peach and orange juice. A complete inhibition activity against Staphylococcus aureus and Escherichia coli in orange juice was observed within 24 h. After 24 h, log 1 and log 2 were obtained in a peach juice containing Staphylococcus aureus and Escherichia coli, respectively. Results of HPLC indicated that Chlorogenic and Chicoric acid compounds were increased in transgenic plants, but this increase was not significant. The study of determining the genetic stability of transgenic plants in comparison with non-transgenic plants showed high genetic stability between non-transgenic plants and transgenic plants. This study confirmed the significant inhibitory effect of nisin protein on gram-positive and gram-negative bacteria.

Combined antimicrobial effect of bacteriocins with other hurdles of physicochemic and microbiome to prolong shelf life of food: A review

Bacteriocins are ribosomally synthesized peptides to inhibit food spoilage bacteria, which are widely used as a kind of food biopreservation. The role of bacteriocins in therapeutics and food industries has received increasing attention across a number of disciplines in recent years. Despite their advantages as alternative therapeutics over existing strategies, the application of bacteriocins suffers from shortcomings such as the high isolation and purification cost, narrow spectrum of activity, low stability and solubility and easy enzymatic degradation. Previous studies have studied the synergistic or additive effects of bacteriocins when used in combination with other hurdles including physics, chemicals, and microbes. These combined treatments reduce the adverse effects of chemical additives, extending the shelf life of food products while guaranteeing food quality. This review highlights the advantages and disadvantages of bacteriocins in food preservation. It then reviews the combined effect and mechanism of different hurdles and bacteriocins in enhancing food preservation in detail. The combination of bacterioncins and other hurdles provide potential approaches for maintaining food quality and food safety.

Conditions of nisin production by Lactococcus lactis subsp. lactis and its main uses as a food preservative

Nisin is a small peptide produced by Lactococcus lactis ssp lactis that is currently industrially produced. This preservative is often used for growth prevention of pathogenic bacteria contaminating the food products. However, the use of nisin as a food preservative is limited by its low production during fermentation. This low production is mainly attributed to the multitude of parameters influencing the fermentation progress such as bacterial cells activity, growth medium composition (namely carbon and nitrogen sources), pH, ionic strength, temperature, and aeration. This review article focuses on the main parameters that affect nisin production by Lactococcus lactis bacteria. Moreover, nisin applications as a food preservative and the main strategies generally used are also discussed.