Cocoa Powder as Delivery Medium for Probiotic Lactobacillus Strains

Three Lactobacillus strains previously isolated from artisanal Italian cheeses and identified by species-spe- cific PCR as L. helveticus, L. paracasei and L. rhamnosus, were evaluated for the presence of functional traits, such as acidifying activity, cell surface hydrophobicity, antibiotic resistance, survival in low pH and in presence of bile salts, in comparison with two commercially available probiotic strains (Lactobacillus aci- dophilus La-5 and L. rhamnosus GG). Subsequently, with the aim to develop a new non-dairy functional product, cocoa powder was used as a medium for incorporating freeze-dried cultures of each tested strain and survival at different time/temperature conditions was investigated. The results obtained demonstrated that artisanal dairy products are interesting sources of new probiotic strains; in particular, the dairy origin strain L. rhamnosus showed a good probiotic performance and the highest level of survival during storage. Finally, we showed that cocoa powder represents a good delivery medium for lactobacilli: it could be considered a novel functional food exhibiting high antioxidant power and presenting probiotic potentia

Genome sequences of two Lactococcus garvieae strains isolated from meat

Lactococcus garvieae is an important fish pathogen and an emerging opportunistic human pathogen, as well as a component of natural microbiota in dairy and meat products. We present the first report of genome sequences of L. garvieae I113 and Tac2 strains isolated from a meat source

16S-23S rRNA intergenic spacer region sequence variation in Streptococcus thermophilus and related dairy streptococci and development of a multiplex ITS-SSCP analysis for their identification

The 16S-23S rRNA internal transcribed spacer (ITS) region of several Streptococcus thermophilus strains and some related dairy streptococci, S. macedonicus, S. salivarius and S. bovis, was analysed by sequence analysis. All the Streptococcus species were easily discriminated on the basis of sequence variations principally located upstream and downstream of the region encompassing the double-stranded processing sites and the tRNA(Ala) gene. Comparison between tRNA(Ala) gene sequences highlighted a high level of sequence conservation among the Streptococcus species investigated despite their belonging to separated phylogenetic clusters, i.e. the S. salivarius and S. bovis rRNA groups. A low but significant degree of variability was detected among the S. thermophilus strains, allowing the identification of four different ITS sequences. Similarity analysis of the ITS sequences showed that the Streptococcus species were clustered in two main branches, one containing S. macedonicus and S. bovis strains, and one containing S. thermlophilus and S. salivarius strains. With the aim of developing a rapid tool for the identification of the dairy streptococci species a multiplex ITS-SSCP analysis of two discrete regions within the ITS locus was carried out

Different strategies to enhance mould-free bread shelf life

The prevention of fungal spoilage of bread without addition of chemical preservatives remains an unsolved issue. This work aimed to identify alternative strategies to chemical preservatives in order to prevent or delay fungal spoilage of bread. The minimum inhibitory concentration (MIC) of bacterial metabolites and chemical preservatives was evaluated in vitro and in situ in baking experiments with addition of preservatives or metabolites. Calcium propionate, sorbic acid, phenyl lactate, ricinoleic acid, and acetic acid were tested both individually and in combination at their MIC values against A. niger and P. roqueforti (12, 0.4, 50, 3.4, 25 mM, respectively). The combination of acetic acid with propionate and sorbate decreased the MIC values against the tested moulds. For these reasons, we introduced sourdough fermentation with defined strains of lactobacilli in order to generate natural acetate in bread. A combination of Lactobacillus hammesii and propionate reduced propionate concentration required for shelf life extension of wheat bread 7 fold. Flaxseed sourdough bread fermented with L. hammesii, showed a shelf life 2 days longer than the control bread. The organic acid quantification indicated a higher production of acetic acid (33.81 \ub1 4.43 mM) when compared to other sourdough breads. When 4% of sucrose was added to sourdough fermentation with L. brevis, the longest mould free shelf-life (4 days longer then the control) was obtained. In conclusion, the in vitro MIC of bacterial metabolites and preservatives matches the in situ antifungal effect. Of the different bacterial metabolites evaluated, acetic acid has the most prominent and consistent antifungal activity and the use of sourdough fermentation with selected strains able to produce acetic acid allows reduced use of chemical preservatives

I prodotti lattiero-caseari

The functional characteristics of Gram-strains isolated in milk products have been reported. The bacteria described belong to group II: technological contaminants

Characterization of Lactobacillus helveticus strains isolated from cheeses by distribution studies of insertion sequences

A collection of 38 Lactobacillus helveticus strains, isolated from a no. of different artisan Italian cheeses, and 4 ref. strains were studied with respect to the presence of insertion sequences and their distribution and abundance. The mobile genetic element ISLh1, that contains one open reading frame coding for a putative transposase of the IS982 family, was used for DNA fingerprinting, together with IS1201 and ISL2, previously isolated from L. helveticus. The no. of insertion sequences per strain and the size of DNA restriction fragments contg. them, was variable and allowed the discrimination at the strain-level. The genomic distribution of the three unrelated insertion sequences showed significant correlations and allowed the differentiation of the strains also with regard to the specific ecol. niche of origin of the isolates. Consequently, insertion sequences comparison may be useful in detg. the history of a group of strains known to be related because of identity and offers a further parameter for evaluating the population polymorphism in L. helveticus. [on SciFinder (R)

Thermostable alkaline protease produced by Bacillus thermoruber, a new species of Bacillus

\u2022 The proteolytic activity produced by a new species of Bacillus isolated in our laboratory was investigated. This enzyme was purified to homogeneity from cell-free culture liquids of B. thermoruber. The purification procedure included ion-exchange chromatography on DEAE-Sephadex A-50 and -casein agarose affinity chromatography. The protease consists of one polypeptide chain with a molecular weight of 39000\ub1800. the isoelectric point was 5.3; the optimum pH and temperature for proteolytic activity (on casein) was found to be pH 9 and 45\ub0C respectively. Enzyme activity was inhibited by PMSF and EDTA. The stability was considerably increased by addition of Ca2+, and the protease exhibited a relatively high thermal stability. The alkaline protease shows a preference for leucine in the carboxylic side of the peptide bond of the substrate. The K m value for benzyloxycarbonyl-Ala-Ala-Leu-p-nitroanilide was 2.5 mM