Eugenio Parente's Articles: (7)
AbstractStrains of Lactobacillus delbrueckii ssp. bulgaricus, Lactobacillus helveticus, Lactobacillus acidophilus, and Streptococcus thermophilus varied in their ability to grow in whey permeate-based media. Whey permeate alone was a poor medium with a relatively low buffering capacity, which supported the growth of L. delbrueckii ssp. bulgaricus and S. thermophilus only. External pH control and the addition of .1% nonfat dry milk solids and .5 to 1% yeast extract improved the growth and activity of L. delbrueckii ssp. bulgaricus, L. helveticus, and S. thermophilus and made whey permeate-based media comparable with 11% nonfat dry milk as a medium for thermophilic lactic acid starters. Internal pH control, using a phosphate buffer, did not significantly improve the growth of the strains used when compared with the unbuffered medium and was inhibitory to L. helveticus 880.
Highlights•32 Lactobacillus plantarum strains were screened for probiotic properties in vitro.•A semi-quantitative scale was used to calculate a “probiotic score”.•Multidimensional scaling was used to represent the pattern of probiotic properties.•Strains source correlated with the probiotic scores.
Highlights•The initial quality of commercial high moisture Mozzarella was extremely variable.•Pseudomonas and psychrotrophs dominated at the end of refrigerated storage.•The acidification mode significantly affected the microbiological quality.•Electronic nose profiles correlated with storage time and microbial counts.•The electronic nose was partially successful in discriminating samples.
AbstractA novel statistical procedure for the analysis of microbial communities based on phenotypic properties of randomly collected isolates is presented and discussed. The procedure allows the representation of the microbial communities as a set of ellipses in a bidimensional graph. This representation is obtained by the following steps: (a) measurement of a set of binary phenotypic properties for n isolates belonging to k samples, each representing a different community; (b) repeated sampling by bootstrapping of the m samples, thus obtaining, for each community, i subsamples of j isolates; (c) calculation of the frequency of positive results for each test for each subsample; (d) calculation of the matrix of Euclidean distances between the k×i frequency vectors; (e) use of multidimensional scaling (MDS) to obtain a representation in two dimensions of the distance relationships between the frequency vectors; (f) plotting of the 95% confidence ellipses for the i frequency vectors of each of the k communities. By using both simple, synthetic microbial communities, and samples of lactic acid bacteria isolated from natural microbial communities (sourdoughs, compressed yeast, fermented sausages), it was demonstrated that the position and shape of the ellipses are clearly related to the composition of the community, while the relationship between the size of the ellipses and the phenotypical diversity of the community is less straightforward: while communities with very different diversity (measured with the Functional Evenness index and the mean taxonomic distance) had ellipses that were very different in size, there was no strict proportionality between the size of the ellipse and the diversity of the community. Nevertheless, the representation of microbial communities obtained by bootstrapping and multidimensional scaling appears to be superior to the more usual representation based on tabulation of the frequencies of isolates belonging to different clusters.
Highlights•FoodMicrobionet 3.0 is the largest curated assembly of data of food microbiomes.•The database makes accessible data from 44 studies.•An interactive app can be used to explore, extract and export data.
AbstractThe objective of this work was to investigate the structure and diversity of lactic acid bacteria (LAB) communities in sourdough used for the production of traditional breads (Carasau, Moddizzosu, Spianata, Zichi) in Sardinia. 16S rDNA sequencing and Randomly Amplified Polymorphic DNA (RAPD-PCR) was applied for the identification and typing of the LAB isolated from 25 samples of sourdoughs. Multivariate statistical techniques were applied to RAPD-PCR pattern to study the biological diversity of sourdough samples. Twelve different species of LAB were identified, and most isolates were classified as facultative heterofermentative lactobacilli. Lactobacillus pentosus dominated the lactic microflora of many samples while Lactobacillus sanfranciscensis was isolated only from a limited number of samples. Although heterofermentative species represented between between 30% and 60% of the isolates in Carasau, Spianata and Zichi sourdoughs, only 2% of the isolates from Moddizzosu sourdoughs were identified as heterofermentative LAB. RAPD-PCR with a single primer followed by cluster analysis did not allow the identification of the isolates at the species level. However, a multidimensional scaling/bootstrapping approach on the RAPD-PCR patterns uncovered the diversity of the LAB communities of LAB showing differences both within and between bread types.
AbstractLactobacillus plantarum is a facultative heterofermentative lactic acid bacterium widely used in the production of most fermented food due to its ability to thrive in several environmental niches, including the human gut. In order to cope with different growth conditions, it has developed complex molecular response mechanisms, characterized by the induction of a large set of proteins mainly regulated by HrcA and CtsR repressors as well as by global regulators such as carbon catabolite control protein A (CcpA).In this study, the role of CcpA in the regulation of growth under anaerobiosis and aerobiosis, and the adaptation to aeration in L. plantarum WCFS1 were comprehensively investigated by differential proteomics. The inactivation of ccpA, in both growth conditions, significantly changed the expression level of 76 proteins, mainly associated with carbohydrate and energy metabolism, membrane transport, nucleotide metabolism, protein biosynthesis and folding. The role of CcpA as pleiotropic regulator was particularly evident at the shift from homolactic fermentation to mixed fermentation. Proteomic results also indicated that the mutant strain was more responsive to aerobic growth condition.