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Thirty-one lactic acid bacterial strains from different species were evaluated for exopolysaccharide (EPS) production in milk. Thermophilic strains produced more EPS than mesophilic ones, but EPS yields were generally low. Ropiness or capsular polysaccharide formation was strain dependent. Six strains produced high-molecular-mass EPS. Polymers were classified into nine groups on the basis of their monomer composition. EPS from Enterococcus strains were isolated and characterized.Certain lactic acid bacteria (LAB) produce exopolysaccharides (EPS), either capsular polysaccharides (CPS) that are tightly associated with the cell surface or slime EPS that are secreted into the extracellular environment. EPS from LAB can be divided into homopolysaccharides, which are polymers composed of one type of monosaccharide, and heteropolysaccharides (HePS), which are polymers of repeating units that are composed of two or more types of monosaccharides (5,6,7,11). A large biodiversity of HePS from LAB exists regarding their composition and structure, molecular mass (MM), yield, and functionalities (5,7,35). Further, polymer formation is strongly influenced by culture conditions (1,7,22,32). Recently, the molecular genetics of HePS biosynthesis have been studied for different LAB species (6, 25). Several glycosyltransferases involved in the assemblage of the HePS repeating units have been discovered (17,18,35). EPS can act as viscosifying, stabilizing, gel-forming, and/or water-binding agents in various foods (6, 10). Additionally, they have been claimed to display properties beneficial to health (6, 29). Little attention has been paid to CPS formation by food grade LAB. Exploration of the biodiversity of wild LAB strains is the most suitable approach to search for a desired EPS phenotype (28,33,34). The aims of this study were to seek new EPS-producing LAB strains, to characterize their biopolymers, and to explore their diversity to find novel or interesting HePS or HePS-producing strains.EPS screening, isolation, and characterization. Two hundred one thermophilic (11 strains of Lactobacillus acidophilus, 79 of Lactobacillus delbrueckii subsp. bulgaricus, 1 of L. delbrueckii subsp. lactis, 1 of Streptococcus macedonicus, and 42 of Streptococcus thermophilus) and mesophilic (23 strains of Enterococcus faecalis, 1 of Enterococcus faecium, 5 of Lactobacillus casei, 29 of Lactobacillus paracasei, and 9 of Lactobacillus rhamnosus) LAB strains (CERELA Culture Collection, Tucumán, Argentina) were used throughout this study. All bacteria were stored as previously described (22). Before experimental use, cultures were propagated twice in MRS (Britania, Buenos Aires, Argentina) for lactobacilli or in LAPTg (27) for streptococci and enterococci.Screening for EPS-producing LAB was performed with reconstituted skim milk (10%, wt/vol) at 37°C for 16 h using cultures propagated in milk as the inoculum (1%, vol/vol). Noninoculated medium was used as a control. Cell counts, expressed as numbers of CFU per milliliter, were determined by pour pla...

Aims: Isolation of bacteriocinogenic lactic acid bacteria (LAB) from the Malaysian mouldfermented product tempeh and characterization of the produced bacteriocin(s). Methods and Results: LAB were present in high numbers in ®nal products as well as during processing. Isolates, Enterococcus faecium B1 and E. faecium B2 (E. faecium LMG 19827 and E. faecium LMG 19828, respectively) inhibited Gram-positive indicators, including Listeria monocytogenes. Partially puri®ed bacteriocins showed a proteinaceous nature. Activity was stable after heat-treatment except at alkaline pH values. Both strains displayed a bacteriostatic mode of action. Bacteriocin production was associated with late exponential/early stationary growth. Molecular mass, calculated by SDS-PAGE, was 3á4 kDa for B1 bacteriocin, and 3á4 kDa and 5á8 kDa for B2 bacteriocins. PCR screening of enterocin-coding genes revealed three ampli®ed fragments in total genomic DNA that may correspond with PCR signals for enterocin P, enterocin L50A and enterocin L50B. Both B1 and B2 contained a 42-kb plasmid. No differences in bacteriocinogenic capacity were found between wild type strains and plasmidcured strains. Conclusions: It was possible to isolate bacteriocinogenic E. faecium active against various Gram-positive bacteria from ®nal products of tempeh. Signi®cance and Impact of the Study: A ®rst step in applying biopreservation to fermented South-east Asian foods is to obtain bacteriocinogenic LAB from this source. Such isolates may also be used for biopreservation of mould-fermented foods in general, including various types of mould-ripened cheese.

Seventy-eight Enterococcus faecium strains from various sources were characterized by random amplified polymorphic DNA (RAPD)-PCR, amplified fragment length polymorphism (AFLP), and pulsed-field gel electrophoresis (PFGE) analysis of SmaI restriction patterns. Two main genomic groups (I and II) were obtained in both RAPD-PCR and AFLP analyses. DNA-DNA hybridization values between representative strains of both groups demonstrated a mean DNA-DNA reassociation level of 71%. PFGE analysis revealed high genetic strain diversity within the two genomic groups. Only group I contained strains originating from human clinical samples or strains that were vancomycin-resistant or beta-hemolytic. No differentiating phenotypic features between groups I and II were found using the rapid ID 32 STREP system. The two groups could be further subdivided into, respectively, four and three subclusters in both RAPD-PCR and AFLP analyses, and a high correlation was seen between the subclusters generated by these two methods. Subclusters of group I were to some extent correlated with origin, pathogenicity, and bacteriocinogeny of the strains. Host specificity of E. faecium strains was not confirmed.