Effect of Polydextrose on the Growth of Pediococcus pentosaceus as Well as Lactic Acid and Bacteriocin-like Inhibitory Substances (BLIS) Production.

Pediococcus pentosaceus was cultivated in MRS medium supplemented or not with polydextrose under different conditions in order to evaluate its effect on cell growth, lactic acid and bacteriocin-like inhibitory substance (BLIS) production. Independent variables were pH (4.0, 5.0, 6.0), rotational speed (50, 100, 150 rpm), polydextrose concentration (0.5, 1.0, 1.5%) and temperature (25, 30, 35 °C), while cell concentration and productivity after 24 h, maximum specific growth rate, specific rate of substrate (glucose) consumption, volumetric and specific lactic acid productivities, yields of biomass and lactic acid on consumed substrate were the dependent. The maximum cell concentration (10.24 ± 0.16 gX L-1) and productivity (0.42 ± 0.01 gX L-1 h-1) were achieved at pH 6.0, 35 °C, 150 rpm using 1.5% polydextrose, while the maximum specific growth rate (0.99 ± 0.01 h-1) and yield of biomass (2.96 ± 0.34 gX gS-1) were achieved at the same pH and polydextrose concentration, but at 25 °C and 50 rpm. The specific substrate consumption rate (0.09 ± 0.02 gS gX-1 h-1) and the volumetric lactic acid productivity (0.44 ± 0.02 gP L-1 h-1) were maximized at pH 6.0, 35 °C, 50 rpm and 0.5% polydextrose. BLIS produced in this last run displayed the highest antibacterial activity against Escherichia coli, while the same activity was displayed against Enterococcus faecium using 1.5% polydextrose. These results appear to be quite promising in view of possible production of this BLIS as an antibacterial agent in the food industry.

Antibacterial and antifungal activity of crude and freeze-dried bacteriocin-like inhibitory substance produced by Pediococcus pentosaceus.

Pediococcus pentosaceus LBM 18 has shown potential as producer of an antibacterial and antifungal bacteriocin-like inhibitory substance (BLIS). BLIS inhibited the growth of spoilage bacteria belonging to Lactobacillus, Enterococcus and Listeria genera with higher activity than Nisaplin used as control. It gave rise to inhibition halos with diameters from 9.70 to 20.00 mm, with Lactobacillus sakei being the most sensitive strain (13.50-20.00 mm). It also effectively suppressed the growth of fungi isolated from corn grain silage for up to 25 days and impaired morphology of colonies by likely affecting fungal membranes. These results point out that P. pentosaceus BLIS may be used as a new promising alternative to conventional antibacterial and antifungal substances, with potential applications in agriculture and food industry as a natural bio-controlling agent. Moreover, cytotoxicity and cell death induction tests demonstrated cytotoxicity and toxicity of BLIS to human colon adenocarcinoma Caco-2cells but not to peripheral blood mononuclear cells, with suggests possible applications of BLIS also in medical-pharmaceutical applications.

Effects of pH and sugar supplements on bacteriocin-like inhibitory substance production by Pediococcus pentosaceus.

To improve bacteriocin-like inhibitory substance (BLIS) production by Pediococcus pentosaceus ATCC 43200, the influence of pH as well as the addition of sugars-either prebiotic (inulin) or not (sucrose)-on its metabolism were investigated. This strain was grown at pH 5.0 or 6.0 either in glucose-based MRS medium (control) or after addition of 0.5, 1.0 or 1.5% (w/w) sucrose and inulin (GSI-MRS) in the same percentages. In the control medium at pH 5.0, cell mass concentration after 48 h of fermentation (Xmax = 2.26 g/L), maximum specific growth rate (µmax = 0.180 h-1) and generation time (Tg = 3.84 h) were statistically coincident with those obtained in supplemented media. At pH 6.0 some variations occurred in these parameters between the control medium (Xmax = 2.68 g/L; µmax = 0.32 h-1; Tg = 2.17 h) and the above supplemented media (Xmax = 1.90, 2.52 and 1.86 g/L; µmax = 0.26, 0.33 and 0.32 h-1; Tg = 2.62, 2.06 and 2.11 h, respectively). Lactate production was remarkable at both pH values (13 and 16 g/L) and improved in all supplemented media, being 34 and 54% higher than in their respective control media, regardless of the concentration of these ingredients. Cell-free supernatant of the fermented control medium at pH 5.0 displayed an antimicrobial activity against Enterococcus 101 5.3% higher than that at pH 6.0 and even 20% higher than those of all supplemented media, regardless of the concentration of supplements. BLIS production was favored either at pH 5.0 or in the absence of any additional supplements, which were able, instead, to stimulate growth and lactate production by P. pentosaceus.

Application of nisin as biopreservative of pork meat by dipping and spraying methods.

Comparison between dipping and spraying methods to inhibit bacterial growth on artificially contaminated pork meat showed greater effectiveness of the latter method during the whole low-temperature one-week storage of product. These results suggest that the spraying method could be successful in directly applying antimicrobials to food products.

Stimulating Effects of Sucrose and Inulin on Growth, Lactate, and Bacteriocin Productions by Pediococcus pentosaceus.

Sucrose and inulin, when combined with glucose, behaved as stimulating agents of bacteriocin production by Pediococcus pentosaceus ATCC 43200. When such microbial strain was grown in glucose-based Man, Rogosa, and Sharpe (MRS) medium, without any additional supplement, it showed higher maximum cell concentration (2.68 ± 1.10 g/L) and longer generation time (2.17 ± 0.02 h), but lower specific growth rate (0.32 ± 0.01 h-1) than in the same medium supplemented with 1.0% of both ingredients (2.53 ± 1.10 g/L, 1.60 ± 0.05 h and 0.43 ± 0.02 h-1, respectively). Glucose replacement by sucrose or inulin almost completely suppressed growth, hence confirming that it is the preferred carbon source for this strain. Qualitatively, similar results were observed for lactate production, which was 59.8% higher in glucose-based medium. Enterococcus and Listeria strains were sensitive to bacteriocin, whose antimicrobial effect after 8 h increased from 120.25 ± 0.35 to 144.00 ± 1.41 or 171.00 ± 1.41 AU/mL when sucrose or inulin was added to the glucose-based MRS medium. Sucrose and inulin were also able to speed up P. pentosaceus growth in the exponential phase.