The kinetics, control, and efficiency of nisin-induced expression directed by the nisA promoter region were studied in Lactococcus lactis with transcriptional and translational fusions to the gusA reporter genes. In the nisin-producing L. lactis strain NZ9700, the specific beta-glucuronidase activity increased very rapidly after mid-exponential growth until the maximum level at the start of the...

Batches of fromage blanc, a soft white cheese were prepared from whole pasteurized cow’s milk. Processing and formulation methods were used in cheese making to reduce Listeria monocytogenes in artificially contaminated cheese. Treatments implemented included use of additional starter culture in formulation (25% more starter culture than original formulation), use of a higher temperature drainin...

Sections of UV sterilized lean and adipose tissues from the surfaces of post-rigor (24 h post-mortem) beef carcasses were inoculated with Brochothrix thermosphacta or Listeria innocua to obtain approximately 4·50 log10 cfu cm and subjected to spray treatments with sterile water or nisin (5000 AU ml). Untreated and spray treated samples were vacuumpackaged, and incubated at 4°C for up to 4 weeks...

The lantibiotic nisin has been used as an effective food preservative to combat food-borne pathogens for over 40 y. Despite this successful use, nisin's stability at pH 7 is limited. Herein, we describe a nisin analog encoded on the genome of the thermophilic bacterium Geobacillus thermodenitrificans NG80-2. This analog termed geobacillin I was obtained by heterologous expression in Escherichia...

The aim of this study was to evaluate the potential of nisin and high pH to inhibit the growth of Staphylococcus aureus and Salmonella sp. in broth culture and when inoculated into meat of land crab. In pure cultures, the growth of S. aureus was strongly inhibited by nisin and the growth of Salmonella sp. was inhibited by nisin– EDTA (20 mM). The inhibition of S. aureus lasted for eight hours a...

The small antimicrobial peptide nisin, produced by Lactococcus lactis, contains the uncommon amino acid residues dehydroalanine and dehydrobutyrine and five thio ether bridges. Since these structures are posttranslationally formed from Ser, Thr, and Cys residues, it is feasible to study their role in nisin function and biosynthesis by protein engineering. Here we report the development of an ex...

Combined effect of whey protein isolate and low temperature with nisin on survival of Bacillus licheniformis were investigated. Sterile imitated milk solution prepared from casein, milk fat, lactose and distilled water was mixed with different whey protein isolate levels of 0, 1, 2 and 4% (w/v) and 100 IU/ml nisin. After mixed thoroughly, the milk solution was aseptically inoculated with 3.74-3...

The aim of this study was to investigate a novel delivery system containing D-limonene and nisin by food organogel-nanoemulsion and study its effect on the antimicrobial activity. Organogel-nanoemulsion containing with D-limonene and nisin or without nisin was prepared by a homogenization method. Factors that may affect the droplet size and stability of organogel-nanoemulsion such as pressure a...

Bacteriocinogenic cultures can represent a natural way to increase the safety of cheeses made from raw milk, in which a relevant role in ripening and flavor formation is exerted by the nonstarter lactic acid bacteria (NSLAB). Since the latter can be inhibited by bacteriocin producers, this study evaluated to which extent a nisinogenic culture inoculated at low initial levels can affect the grow...

A two-temperature agar diffusion bioassay is commonly used to quantify the concentration of nisin using Micrococcus luteus as the indicator microorganism. A finite element computational model based on Fick's second law of diffusion was used to predict the radius of the inhibition zone in this diffusion bioassay. The model developed was used to calculate nisin concentration profiles as a functio...