A stochastic interspecific competition model to predict the behaviour of Listeria monocytogenes in the fermentation process of a traditional Sicilian salami

In this research, two competition indexes, competing capacity and competing tensor, are brought forward to better understand the interspecific competition between species. With the employment of the two indexes, the competitive process in Lotka-Volterra model can be described much clearly. The strength of competition for a species is divided into three competition grades according to the competing tensor. In the interspecific competition, when two species are in different competition grades, the weak species will be excluded; when two species are in the same grade, the coexistent equilibrium will present. Two cases are studied with the methods by employing the two indexes. In the second case, the stability of equilibrium point is determined by the competing tensor. The new indexes have shown potential in population dynamics analysis.

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EFFECTS OF REFUGES AND DENSITY DEPENDENT DISPERSAL ON INTERSPECIFIC COMPETITION DYNAMICS

International Journal of Bifurcation and Chaos ◽

10.1142/s0218127412500290 ◽

2012 ◽

Vol 22 (02) ◽

pp. 1250029 ◽

Cited By ~ 4

Author(s):

NGUYEN-NGOC DOANH ◽

NGUYEN-HUU TRI ◽

AUGER PIERRE

Keyword(s):

Interspecific Competition ◽

Competition Model ◽

Density Dependent ◽

First Case ◽

Global Extinction ◽

Density Dependent Dispersal ◽

Effects Of Density

We present a classical interspecific competition model. Individuals compete for a resource on a common patch and can go to a refuge. It is assumed that if species would remain on the competition patch, species 1 survives and species 2 would go extinct. Therefore, species 1 is Locally Superior Competitor (LSC) and species 2 Locally Inferior Competitor (LIC). We study the effects of density dependent dispersal from the competition patch to the refuge on the global outcome of competition. We study two cases. The first case considers LSC density dependent dispersal of the LIC trying to escape competition and going to its refuge when the LSC density is large. The second case considers aggressiveness of LIC leading to LIC density dependent dispersal of the LSC. We show that under some conditions, tactic 2 can allow the LIC to survive and even provoke global extinction of the LSC.

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Development of interspecific competition models for the growth of Listeria monocytogenes and Lactobacillus on vacuum-packaged chilled pork by quantitative real-time PCR

Food Research International ◽

10.1016/j.foodres.2014.07.017 ◽

2014 ◽

Vol 64 ◽

pp. 626-633 ◽

Cited By ~ 12

Author(s):

Keping Ye ◽

Huhu Wang ◽

Yun Jiang ◽

Xinglian Xu ◽

Jinxuan Cao ◽

...

Keyword(s):

Listeria Monocytogenes ◽

Interspecific Competition ◽

Real Time ◽

Real Time Pcr ◽

Quantitative Real Time Pcr ◽

Competition Models ◽

Chilled Pork

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Prediction of alpine artificial grassland restoration based on an improved Lotka-Volterra interspecific competition model

Acta Ecologica Sinica ◽

10.5846/stxb201806091293 ◽

2019 ◽

Vol 39 (9) ◽

Author(s):

吴晓慧 WU Xiaohui ◽

单熙凯 SHAN Xikai ◽

董世魁 DONG Shikui ◽

高晓霞 GAO Xiaoxia ◽

许驭丹 XU Yudan ◽

...

Keyword(s):

Interspecific Competition ◽

Competition Model ◽

Grassland Restoration ◽

Artificial Grassland

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Application of Enterococcus faecium KE82, an enterocin-A-B-P-producing strain, as an adjunct culture enhances inactivation of Listeria monocytogenes during traditional PDO Galotyri cheese processing

Journal of Food Protection ◽

10.4315/jfp-20-278 ◽

2020 ◽

Author(s):

Nikoletta Sameli ◽

Panagiotis N Skandamis ◽

John Samelis

Keyword(s):

Listeria Monocytogenes ◽

Enterococcus Faecium ◽

Fermentation Process ◽

Streptococcus Thermophilus ◽

Milk Fermentation ◽

Dairy Plant ◽

Ewe's Milk ◽

Cheese Curd ◽

Enterocin A ◽

Adjunct Culture

The ability of the enterocin-A-B-P-producing Enterococcus faecium KE82 adjunct strain to inactivate Listeria monocytogenes during Galotyri PDO cheese processing was evaluated. Three artisan cheese trials from traditionally ‘boiled’ (85oC) ewe’s milk were processed. The milk cooled at 42oC was divided in two parts: A1 was inoculated with Streptococcus thermophilus ST1 and Lactococcus lactis subsp. cremoris M78, and A2 with the basic starter ST1+M78 plus the KE82 adjunct (step 1). All milks were fermented at 20-22oC for 24 h (step 2); the curds were drained at 12oC for 72 h (step 3) and then salted with 1.5-1.8% salt to obtain the fresh Galotyri cheeses (step 4), which were ripened at 4oC for 30 days (step 5). Because an artificial listerial contamination in the dairy plant was prohibited, A1 and A2 cheese milk (200-mL) or curd (200-g) portions were taken after steps 1 to 5, inoculated (3-4 log CFU/mL or g) with L. monocytogenes no.10, incubated at 37, 22, 12, and 4oC for predefined periods, and analyzed microbiologically and for pH. L. monocytogenes declined without growth in all cheese curd portions contaminated after steps 2 to 5 (pH 4.36 to 4.84), when stored at 4 or 12oC for 15 days. The final net reductions of Listeria populations were by 2.00, 1.07, 0.54 and 0.61 log units higher in the A2 than A1 curd portions after steps 2, 3, 4 and 5, respectively. As regards step 1 conducted in simulation of the whole cheese milk fermentation process, L. monocytogenes declined by 1.47 log units more in the A2 than A1 milk portions after 72 h at 22oC; however, a slight (0.6-log) growth was preceded during the first 6 h at 37oC. In conclusion, E. faecium KE82 showed growth compatibility with the starter and enhanced inactivation of L. monocytogenes across Galotyri cheese processing. Combined acid-enterocin antilisterial effects were the weakest in the fermenting milks, turned to the strongest in the unsalted fermented curds, and reduced in the salted fresh cheeses.

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Survival of Listeria monocytogenes in Refrigerated Cultured Milks and Yogurt

Journal of Food Protection ◽

10.4315/0362-028x-51.11.848 ◽

1988 ◽

Vol 51 (11) ◽

pp. 848-852 ◽

Cited By ~ 21

Author(s):

MICHELLE M. SCHAACK ◽

ELMER H. MARTH

Keyword(s):

Listeria Monocytogenes ◽

Fermentation Process ◽

Skim Milk ◽

Lactobacillus Bulgaricus ◽

Refrigerated Storage ◽

Streptococcus Lactis ◽

Inoculum Survival

Skim milks containing Listeria monocytogenes were fermented at 21, 30, 37 or 42°C for 15 h with Streptococcus lactis, S. cremoris, S. thermophilus, Lactobacillus bulgaricus or L. bulgaricus plus S. thermophilus (LBST). Amounts of inocula were 5.0, 1.0, 0.5 or 0.1%. Yogurt mix was inoculated with L. monocytogenes and fermented at 45°C for 5 h. Cultured skim milks and yogurt were stored at 4°C and sampled weekly to monitor survival of L. monocytogenes and the pH. Yogurt was sampled ca. every 3 d for enumeration of L. monocytogenes and determination of pH. Results show that L. monocytogenes survived longest in skim milks fermented with S. thermophilus, ranging from 4 weeks in skim milk fermented at 42°C with a 5.0% inoculum (final pH 4.62) to 37 weeks in skim milk fermented at 37°C with a 1.0% inoculum (final pH 4.52). When skim milks were fermented with S. lactis, L. monocytogenes survived from 2 weeks (5.0% inoculum, 30°C incubation, final pH 4.20) to more than 13 weeks (0.1% inoculum, 21°C incubation, final pH 4.70). L. monocytogenes survived from 4 (final pH 4.36) to 13 (final pH 5.30) weeks in milk fermented with S. cremoris. L. bulgaricus was the most detrimental to L. monocytogenes; the pathogen survived only 3 d to 1 week in the skim milk fermented at 37°C with 0.1 % inoculum. Survival of L. monocytogenes in milk fermented with LBST culture ranged from 1 (final pH 3.93) to 12 (final pH 4.41) weeks in those skim milks in which the organism survived the fermentation process. L. monocytogenes survived yogurt manufacture and from 1 (final pH 4.13) to 12 (final pH 3.93) d during refrigerated storage of the product.

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