Inhibitory activity of Lactobacillus curvatus CWBI-B28 against Listeria monocytogenes and ST2-verotoxin producing Escherichia coli O157

A bacteriocin-producing strain of Lactobacillus curvatus CWBI-B28 isolated from raw meat was shown to inhibit Listeria monocytogenes and pathogenic strains of Escherichia coli by the well diffusionassay. To confirm whether the bacteriocin was involved in E. coli O157 inhibition, growth of the pathogen was monitored in the neutralized cell-free supernatant (NCFS) pre-treated with pronase E orcatalase. Alternatively, E. coli O157 (VH21) was co-cultured with Lb. curvatus CWBI-B28 in MRS broth. The results of the well-diffusion assay suggested that the inhibition of E. coli O157 (VH21) was partially due to the bacteriocin; however, growth monitoring indicated that such inhibition is exclusively due to hydrogen peroxide. In pronase-added NCFS (i.e., absence of bacteriocin) the colony forming units (cfus) of E. coli O157 (VHA21) declined to below the detectable limit after 24 h of incubation at 37°C. However, in presence of catalase no inhibition of the pathogen was observed and the cfus increasedsteadily to reach 8 log units in 24 h. Moreover, in co-culture, a significantly accelerated inhibition of E. coli O157 (VH21) was observed in MRS broth as compared to the NCFS without added catalase and the cfus decreased to below the detectable limit in 8 h instead of 24 h, respectively

Effect of nisin on the keeping quality of feta cheese

In an attempt to extend cheese shelf-life, nisin was added to Feta cheese during cheese making to achieve a final concentration of 40 lU/ml ofmilk. At this concentration, acid production was slightlyretarded afterthe curd cutting but not completely inhibited. Cheese manufacture proceeded apparently normally yielding a product that met Greek regulatory standards. Chemical analysis showed that nisin addition had no significant effect (P<0.01) on salt, fat or ash contents. However, the total chee se dry matter was significantly reduced. The 8helf-life was shortened to less than 47 days due to intensive growth of Gram negative bacteria not inhibited by nisin. Such organisms were probably stimulated by the inhibition of competitive Gram positive bacteria incIuding, the starter culture, to sorne extent. The shelf-life of the control cheese exceeded 60 days.Résumé:Effet de la nisine sur la conservabilité du fromage FetaDans une tentative d'extension de la durée de conservation du fromage "Feta", la nisine lui a été ajoutée durant sa fabrication à une concentration finale de 40 UI/ml de lait. À cette concentration, la production d'acide a été légèrement affectée après coupure du caillé sans être complètement inhibée. La fabrication du fromage a continué apparemment normalement aboutissant à un produit conforme aux normes grecs. L'analyse chimique a révélé que l'addition de nisine n'avait pas d'effet significatif (P<O,Ol) sur les teneurs en sel, matière grasse et cendres. Cependant, le taux de matière sèche a été significativement réduit. La durée de conservation a été réduite à moins de 47 jours à cause d'une croissance intensive des bactéries à Gram négatif qui ne sont pas inhibées par la nisine. La croissance de ces bactéries a été probablement favorisée par l'inhibition, à un certain degré, des bactéries à Gram positif compétitives comprenant celles du ferment. La durée de conservation du témoin (fromage sans ajout de nisine) a, en revanche, dépassé les 60 jours

Functional similarities between pigeon \u27milk\u27 and mammalian milk : induction of immune gene expression and modification of the microbiota

Pigeon ‘milk’ and mammalian milk have functional similarities in terms of nutritional benefit and delivery of immunoglobulins to the young. Mammalian milk has been clearly shown to aid in the development of the immune system and microbiota of the young, but similar effects have not yet been attributed to pigeon ‘milk’. Therefore, using a chicken model, we investigated the effect of pigeon ‘milk’ on immune gene expression in the Gut Associated Lymphoid Tissue (GALT) and on the composition of the caecal microbiota. Chickens fed pigeon ‘milk’ had a faster rate of growth and a better feed conversion ratio than control chickens. There was significantly enhanced expression of immune-related gene pathways and interferon-stimulated genes in the GALT of pigeon ‘milk’-fed chickens. These pathways include the innate immune response, regulation of cytokine production and regulation of B cell activation and proliferation. The caecal microbiota of pigeon ‘milk’-fed chickens was significantly more diverse than control chickens, and appears to be affected by prebiotics in pigeon ‘milk’, as well as being directly seeded by bacteria present in pigeon ‘milk’. Our results demonstrate that pigeon ‘milk’ has further modes of action which make it functionally similar to mammalian milk. We hypothesise that pigeon ‘lactation’ and mammalian lactation evolved independently but resulted in similarly functional products

Inhibitory activity of lactobacillus curvatus CWBI-B28 against Listeria monocytogenes and ST2-verotoxin producing Escherichia coli O157

peer reviewedA bacteriocin- producing strain of Lactobacillus curvatus CWBI- B28 isolated from raw meat was shown to inhibit Listeria monocytogenes and pathogenic strains of Escherichia coli by the well diffusion assay. To confirm whether the bacteriocin was involved in E. coli O157 inhibition, growth of the pathogen was monitored in the neutralized cell- free supernatant ( NCFS) pre- treated with pronase E or catalase. Alternatively, E. coli O157 ( VH21) was co- cultured with Lb. curvatus CWBI- B28 in MRS broth. The results of the well- diffusion assay suggested that the inhibition of E. coli O157 ( VH21) was partially due to the bacteriocin; however, growth monitoring indicated that such inhibition is exclusively due to hydrogen peroxide. In pronase- added NCFS ( i. e., absence of bacteriocin) the colony forming units ( cfus) of E. coli O157 ( VHA21) declined to below the detectable limit after 24 h of incubation at 37 C. However, in presence of catalase no inhibition of the pathogen was observed and the cfus increased steadily to reach 8 log units in 24 h. Moreover, in co- culture, a significantly accelerated inhibition of E. coli O157 ( VH21) was observed in MRS broth as compared to the NCFS without added catalase and the cfus decreased to below the detectable limit in 8 h instead of 24 h, respectively

Antimicrobial activity of lysozyme with special relevance to milk

Lysozyme is a hydrolytic enzyme which has been purified from cells, secretions and tissues of virtually all living organisms and viruses. While this protein has been recognized to possess many physiologicaland functional properties, its high microbicidal activity remains, by far, the main virtue that explains the high attention of scientists and industrial stakeholders for its practical applications in medicine andfood industry. Although the egg-white is the primary source for lysozyme production at industrial scale, other sources such as milk of mammals should not be overlooked, as they may contain lysozymemolecules with specific properties not present in the conventional egg-white lysozyme. This review discusses the antimicrobial activity of lysozyme with special emphasis on milk’s lysozyme, and attempts to shed some light on the recent advances elucidating the mechanism of its antimicrobial activity against sensitive microorganisms as well as the means used by some bacteria to resist such an activity

Preparation and utilisation of fish silage as feed supplement for ruminants

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