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Lactobacillus plantarum 423, isolated from sorghum beer, produces a bacteriocin (plantaricin 423) which is inhibitory to several food spoilage bacteria and food-borne pathogens, including Bacillus cereus, Clostridium sporogenes, Enterococcus faecalis, Listeria spp. and Staphylococcus spp. Plantaricin 423 is resistant to treatment at 80 degrees C, but loses 50% of its activity after 60 min at 100 degrees C and 75% of its activity after autoclaving (121 degrees C, 15 min). Plantaricin 423 remains active after incubation at pH 1-10 and is inactivated when treated with pepsin, papain, alpha-chymotrypsin, trypsin and Proteinase K. Plantaricin 423 was partially purified and its size estimated at 3.5 kDa, as determined by tricine-SDS-PAGE. The mechanism of activity of plantaricin 423 is weakly bactericidal, as determined against Oenococcus oeni (previously Leuconostoc oenos). High DNA homology was obtained between the plasmid DNA of strain 423 and the pediocin PA-1 operon of Pediococcus acidilactici PAC 1.0, suggesting that plantaricin 423 is plasmid-encoded and related to the pediocin gene cluster.

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Wine strains belonging to the genus Leuconostoc were classified as Leuconostoc oenos by Garvie in 1967, and this name was confirmed on the Approved Lists of Bacterial Names in 1980. L. oenos is distinguished from other Leuconostoc spp. by its growth in acidic media, by its requirement for a growth factor in tomato juice, and by a number of carbohydrate fermentation characteristics, In addition, the results of a total soluble cell protein analysis, an electrophoretic analysis of NAD-dependent D-( -)-lactate dehydrogenase, 6-phosphogluconate dehydrogenase, and alcohol dehydrogenase, and an analysis of cross-reactivity with anti-glucose-6-phosphate dehydrogenase and anti-NAD-dependent (2,5,11,17,19,20). L. amelibiosum is now considered a subjective synonym of L. citreum (21), whereas organisms formerly designated Leuconostoc cremoris and Leuconostoc dextranicum are now classified as subspecies of L. mesenteroides (10). Leuconostoc paramesenteroides has recently been assigned to the new genus Weissella, as Weissella paramesenteroides (1).L. oenos is the only acidophilic member of the genus Leuconostoc and occurs naturally in wine and related habitats (6,11,12). Strains of L. oenos are distinguished from the other Leuconostoc spp. by their growth at an initial pH of 4.8 and in media containing 10% (vol/vol) ethanol, by their requirement for a tomato juice growth factor (most strains), and by their lack of NAD-dependent glucose-6-phosphate dehydrogenase (11). The electrophoretic mobilities of NAD-dependent D-( -)-lactate dehydrogenase, 6-phosphogluconat e de hy dr ogenase, and alcohol dehydrogenase also clearly distinguish L. oenos from the other Leuconostoc spp. (3,7,11,12). Furthermore, antisera prepared from L. oenos exhibit no cross-reactivity with L. lactis anti-glucose-6-phosphate dehydrogenase and anti-NAD-dependent D-( -)-lactate dehydrogenase (14) and L. mesenteroides subsp. mesenteroides anti-glucose-6-phosphate dehydrogenase (13). L. oenos is also distinguished from other Leuconostoc spp. by its total soluble cell protein pattern (4).Further evidence that L. oenos is a distinct taxon comes from genotypic investigations. Chromosomal DNA-DNA pairing has been used extensively to determine the genetic interrelationships of members of the genus Leuconostoc (4,5,8,15,19). Although L. oenos has been shown to be a distinct species by this approach, more significant are the very low levels of DNA * Corresponding author. ~ ~~homology detected between this species and other members of the genus ( (Fig. 1). Yang and Woese (22) and have shown that L. oenos is unusual in that it exhibits a relatively long rRNA branch. It has been suggested by Yang and Woese (22) that this characteristic, together with the phenotypic peculiarities of L. oenos and its negligible levels of DNA homology with other Leuconostoc spp., indicates that L. oenos is a fast-evolving organism. However, irrespective of whether L. oenos is a fast-evolving organism, it is clear from the results of comparative 16s and 23s rRNA sequencing analyses tha...

E ND AA L . 1999. Lactobacillus pentosus TV35b, isolated from the posterior fornix secretions of the vagina of a prenatal patient, produced a bacteriocin-like peptide (pentocin TV35b), which is inhibitory to Clostridium sporogenes, Cl. tyrobutyricum, Lact. curvatus, Lact. fermentum, Lact. sake, Listeria innocua, Propionibacterium acidipropionici, Propionibacterium sp. and Candida albicans. The mechanism of activity of pentocin TV35b is bactericidal, as shown by a decrease in the viable cell numbers of Lact. sake from approximately 4 × 10 8 to less than 10 cfu ml −1 over a period of 4 h. Pentocin TV35b added to the growth medium of C. albicans stimulated the formation of pseudohyphae during the first 36 h, followed by a slight repression in cell growth. Production of pentocin TV35b was at its maximum towards the end of the logarithmic growth phase of strain TV35b. The peptide was purified by ammonium sulphate precipitation, followed by SP-Sepharose cation exchange chromatography. The molecular size of pentocin TV35b was estimated to be between 2·35 and 3·4 kDa, according to tricine-SDS PAGE. However, results obtained by electrospray ionization mass spectroscopy indicated that the peptide is 3930·2 Da in size. Amino acid analysis performed by using the Pico-Tag® method and a Nova-Pak C 18 HPLC column indicated that pentocin TV35b consists of 33 amino acids with a total mass of 3929·63 Da. Pentocin TV35b is inactivated when treated with papain and Proteinase K, but remains active after incubation at pH 1-10 for 2 h at 25°C, and when heattreated for 30 min at 100°C.

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Aims:  To evaluate the probiotic properties of strains isolated from boza, a traditional beverage produced from cereals. Methods and Results:  The strains survived low pH conditions (pH 3·0), grew well at pH 9·0 and were not inhibited by the presence of 0·3% (w/v) oxbile. Cytotoxicity levels of the bacteriocins, expressed as CC50, ranged from 38 to 3776 μg ml−1. Bacteriocin bacST284BZ revealed high activity (EC50 = 735 μg ml−1) against herpes simplex virus type 1. Growth of Mycobacterium tuberculosis was 69% repressed after 5 days in the presence of bacST194BZ. Various levels of auto‐cell aggregation and co‐aggregation with Listeria innocua LMG 13568 were observed. Adhesion of the probiotic strains to HT‐29 cells ranged from 18 to 22%. Conclusions:  Boza is a rich source of probiotic lactic acid bacteria. All strains survived conditions simulating the gastrointestinal tract and produced bacteriocins active against a number of pathogens. Adherence to HT‐29 and Caco‐2 cells was within the range reported for Lactobacillus rhamnosus GG, a well‐known probiotic. In addition, the high hydrophobicity readings recorded define the strains as good probiotics. Significance and Impact of the Study:  Boza contains a number of different probiotic lactic acid bacteria and could be marketed as a functional food product.

Lactic acid bacteria (LAB) have received considerable attention as probiotics over the past few years. This concept has grown from traditional dairy products to a profitable market of probiotic health supplements and functional foods. Extensive research is done on novel potential probiotic strains, with specific emphasis on their health benefits and mode of action. Criteria for the selection of probiotic strains have only recently been formulated by the Food and Agriculture Organization of the United Nations and the World Health Organization (FAO/WHO). Several in vitro techniques have been developed to evaluate the probiotic properties of strains. In many cases, this is followed by in vivo tests. Safety studies are also obligatory, as a few cases of bacteremia caused by LAB have been reported. This review focuses on the health benefits and safety of LAB probiotics, the criteria used to select a probiotic, mode of action and the impact these organisms have on natural microbiota in the gastro-intestinal tract.