Effects of inulin, fructooligosaccharides/glucose and pH on the shape of the death kinetic ofLactobacillus reuteriDSM 20016

Lactiplantibacillus plantarum subsp. plantarum and Fructooligosaccharides Combination Inhibits the Growth, Adhesion, Invasion, and Virulence of Listeria monocytogenes

Listeria monocytogenes is a foodborne pathogen responsible for many food outbreaks worldwide. This study aimed to investigate the single and combined effect of fructooligosaccharides (FOS) and Lactiplantibacillus plantarum subsp. plantarum CICC 6257 (L. plantarum) on the growth, adhesion, invasion, and virulence of gene expressions of Listeria monocytogenes 19112 serotype 4b (L. monocytogenes). Results showed that L. plantarum combined with 2% and 4% (w/v) FOS significantly (p < 0.05) inhibited the growth of L. monocytogenes (3-3.5 log10 CFU/mL reduction) at the incubation temperature of 10 °C and 25 °C. Under the same combination condition, the invasion rates of L. monocytogenes to Caco-2 and BeWo cells were reduced more than 90% compared to the result of the untreated group. After L. plantarum was combined with the 2% and 4% (w/v) FOS treatment, the gene expression of actin-based motility, sigma factor, internalin A, internalin B, positive regulatory factor A, and listeriolysin O significantly (p < 0.05) were reduced over 91%, 77%, 92%, 89%, 79%, and 79% compared to the result of the untreated group, respectively. The inhibition level of the L. plantarum and FOS combination against L. monocytogenes was higher than that of FOS or L. plantarum alone. Overall, these results indicated that the L. plantarum and FOS combination might be an effective formula against L. monocytogenes.

Films of Chitosan and Aloe vera for Maintaining the Viability and Antifungal Activity of Lactobacillus paracasei TEP6

The present study aimed to evaluate the effect of Aloe vera addition on the viability and antifungal activity of TEP6 (Lactobacillus paracasei) bacteria immobilized on chitosan films for 28 days. Different chitosan and A. vera proportions and carbon sources at several pH values were tested as formulations for supporting the microorganism. Bacterial viability was maintained in freshly made films, with values of 10.4, 10.8 and 10.9 log CFU·g−1 for the formulations containing 70% (T11), 100% (T8) and 100% (T16) of A. vera, respectively. The same formulations (T8, T11 and T16) maintained bacterial viability for 14 days of film storage with a loss to values of 9.5 log CFU·g−1. By applying a quarter fraction 25–2 experimental design with an array of five factors, the factors with the greatest influence on viability and antifungal activity were determined. The optimal conditions for viability were the formulation with 100% A. vera, pH 4.5 and 0.1 M glucose. The antifungal activity of fresh films was influenced by the formulation with 10 g·L−1 glycerol and 100% A. vera, showing a 60% inhibition of fungal (Colletotrichum gloeosporioides) growth. The films developed in this study may have the potential to be used as coatings on vegetal products susceptible to attack by Colletotrichum gloesporioides.

The Impact of Gluten Friendly Flour on the Functionality of an Active Drink: Viability of Lactobacillus acidophilus in a Fermented Milk

The Gluten Friendly^TM Technology is an innovative method that induces structural changes in gluten proteins. In this paper a synbiotic fermented milk, containing Lactobacillus acidophilus La-5 and Gluten Friendly Flour (GFF), was proposed. A mixture design was used to combine flour, temperature and probiotic to study the effects of these variables on the acidification. The experiments were done on both GFF and control flour (CF). Thus, the following conditions were chosen to produce the fermented milk: L. acidophilus at 6.5 log cfu/ml; flour at 2.5 g/l; temperature at 37°C. Then, the fermented milk was produced and stored at 4°C for 90 days. The most important result was the positive effect of GFF on the viability of the probiotic, with a prolongation of the shoulder length to 20 days (12–13 days in the control). Moreover, GFF did not act on the sensory scores and on the physico-chemical parameters.

Survival of Listeria monocytogenes and Staphylococcus aureus in Synthetic Brines. Studying the Effects of Salt, Temperature and Sugar through the Approach of the Design of Experiments

The fermentation of table olives relies on a complex microbiota of lactic acid bacteria (LAB), yeasts, and enterobacteria. Producers often add sugar to increase the growth rate of LAB, “but this practice could also increase the survival rate of some pathogens. Therefore, the main topic of this paper was to study the effect of sugar, salt and temperature on the survival of Staphylococcus aureus and Listeria monocytogenes in a synthetic brine through the theory of the Design of Experiments (simplex centroid). The addition of sugar could prolong the survival time of L. monocytogenes by 40 days, whereas an increase of the temperature caused a decrease of survival from 18 to 3 days. The survival time of S. aureus was prolonged by 50 days by combining sugar (2–4 g/l) and low temperatures (5–15°C). The use of desirability approach and prediction profiles suggests that the prolongation of the survival time of L. monocytogenes could be related to a shift in the geometrical shape of the death kinetic. This paper offers a structured statistical approach on the variables acting on the survival of two pathogens in brines and represents the first step to set up and design a predictive approach for olive producers.