Aggregation and hydrophobicity properties of 6 dairy propionibacteria strains isolated from homemade Turkish cheeses.

UNLABELLED: In the present study, 6 dairy Propionibacterium strains were assessed with regard to their hydrophobic characteristics and their autoaggregation and coaggregation abilities since these traits have been shown to be indicative of adherence in other microorganisms. Aggregation assays and bacterial adhesion to hydrocarbons demonstrated significant differences in cell surface properties among the tested propionibacteria strains. Almost all strains appeared relatively hydrophilic, which showed low affinity for p-xylene. Four of the tested strains showed the strong adhesion to ethyl acetate, a basic solvent, in comparison with microbial adhesion to chloroform, an acidic solvent, which demonstrated the particularity of propionibacteria to have an important electron donor and acidic character. Also, these strains simultaneously showed affinity to 3 hydrocarbons, suggesting a high complexity of the cell surface. All propionibacteria strains tested showed autoaggregation and coaggregation ability with the Escherichia coli ATTC 11229, but the results were strain-specific and dependent on incubation conditions. Anaerobic incubation conditions were determined as the best condition for aggregation abilities of propionibacteria strains. A relationship was obtained between aggregation abilities (auto- and coaggregation) and a correlation between adhesion to hydrocarbon (chloroform) and autoaggregation was possible. Our results indicate that the ability to autoaggregation together with cell surface hydrophobicity and coaggregation abilities with E. coli strain can be used for preliminary screening in order to identify potentially probiotic bacteria suitable for human or animal use. PRACTICAL APPLICATION: Autoaggregation, cell surface hydrophobicity, and coaggregation abilities with E. coli of the selected dairy propionibacteria strains could be used as probiotic in foods after in vivo studies.

Analysis of the genetic determinant for production of the pediocin P of Pediococcus pentosaceus Pep1.

Pediococcus pentosaceus Pep1 is a vacuum-packaged Turkish sausage isolate which produces a potentially novel bacteriocin of the pediocin (anti-Listeria) family of peptides designated as pediocin P. Curing experiments and plasmid profile analysis indicated that both bacteriocin immunity and production determinants were linked and encoded by 9.0 MDa plasmid, pHD1.0. Attempts to transform purified plasmid pHD1.0 into recipient Escherichia coli JM109 cells by electroporation were successful but none of the E. coli JM109 cells were able to express and/or release pediocin P. However, P. pentosaceus PC, a plasmid-cured variant of P. pentosaceus Pep1 was successfully transformed with pHD1.0 by electroporation and Bac-Bacs P. pentosaceus PC cells restarted to express and/or release pediocin P again as indicated by the presence of zone of growth inhibition of L. plantarum NCDO 955 around colonies.

Cloning and expression of a plasmid-linked pediocin determinant trait of Pediococcus acidilactici F.

Plasmid DNA from Pediococcus acidilactici F was prepared by lysozyme-mutanolysin method and purified by cesium chloride-ethidium bromide (CsCl-EtBr) density gradient ultracentrifugation. Agarose gel electrophoresis of plasmid DNA and plasmid-curing experiments suggested that bacteriocin activity was harboured on a small plasmid of approximately 9.1 kb (kilobasepair) in Pediococcus acidilactici F. Plasmid encoding bacteriocin production in P. acidilactici F was examined for restriction enzyme cleavage patterns and its map has been constructed. An Escherichia coli strain transformed with the recombinant plasmid, pQE322, produced and, most probably, secreted pediocin F.

Poly-beta-hydroxybutyrate production by lactic acid bacteria.

Poly-beta-hydroxybutyrate was determined in lactic acid bacteria belonging to the genera Lactobacillus, Lactococcus, Pediococcus and Streptococcus. Lactobacilli were grown in MRS broth, the others were grown in Elliker broth medium. Cell biomass was obtained by centrifugation. The cell walls were lysed with sodium hypochlorite. Poly-beta-hydroxybutyrate was extracted using chloroform in a Soxhlet system. Then it was converted to crotonic acid using sulfuric acid and the amount of crotonic acid was measured spectrophotometrically. The yield of poly-beta-hydroxybutyrate (% of cell dry weight) of Lactobacillus species was 6.6-35.8%. The values for Lactococcus, Pediococcus and Streptococcus species were 9.0-20.9, 1.1-8.0 and 6.8-17.2, respectively. It was observed that one of the Lactobacillus species did not produce poly-beta-hydroxybutyrate. Generally, Lactobacillus species produced more poly-beta-hydroxybutyrate than the other tested bacteria and no significant correlation was observed between poly-beta-hydroxybutyrate production and cell density of the cultures.