Autochthonous Lactobacillus paracasei subsp. paracasei strains isolated from Caciocavallo cheese: identification and in-vitro investigation on potential probiotic and functional properties

Background: In recent years consumers, due to the growing interest for functional foods, have put particularly a ention on prod- ucts enriched with probiotic lactic acid bacteria for their ability to give human bene t by their assumption. Microorganisms to be considered as probiotic should be able to survive to gastrointestinal juices and colonize the intestinal tract to provide bene ts to human health. The aim of the study consisted on the in vitro investigation of novel LAB strains, isolated during cheesemaking and ripening of Caciocavallo cheese, and on their probiotic potential for food application. Methods: In order to select potential probiotic bacteria, LAB isolates were preliminarily screened for their survival to simulated gastro-intestinal transitand assayed for others activities of probiotic and functional interest. Thanks to promising a itude as poten- tial probiotics, four strains were tested to evaluate their adhesion ability on Caco-2 cell lines used as intestinal cell model. Microbiological data were analysed by one-way analysis of variance (ANOVA). Comparisons of means were carried out using post-hoc Tukey’s test. For vitro adhesion experiments, statistical signi cance was evaluated by Kruskal-Wallis test for equal medi- ans. Results: Twenty- ve LAB, presumptively identi ed as Lactobacillus spp., were isolated from cheese during 60 days of ripening and screened for their survival to simulated gastrointestinal transit. Sixteen isolates that showed a survival rate ≥85% were identi edas 10 di erent pro les of Lb. paracasei subsp. paracasei. The 10 strains tolerated high concentration of bile salts by Minimal Inhibitory Concentration and growth rate assays and showed susceptibility or moderate susceptibility against antibiotics of human and vet- erinary importance, except for the resistanceto the class of aminoglycoside antibiotics. Eight out 10 strains showed in vitro choles- terol-lowering ability, whereas all strains showed antioxidant activity of their cell-free supernatants. Moreover, the four strains with highest survival to simulated gastrointestinal transit showed the ability to adhere to Caco-2 cells. Conclusion: The results suggest that some strains may be e ective probiotics to be use as tool to design probiotic dairy products after con rmation probiotic activities in further in vivo studies. Findings of the present study suggest that four strains showed good or strong adherent ability on Caco-2 cell monolayer, that is one of prerequisite that probiotic bacteria must have to perform their functional properties

Physical properties and antimicrobial activity of bioactive film based on whey protein and Lactobacillus curvatus 54M16 producer of bacteriocins

The objective of the work was to study the viability and antimicrobial activity of bacteriocin-producing lactic acid bacteria (LAB) incorporated into whey protein/inulin/gelatine (WP) edible films in presence or absence of nutrient (modified MRS broth). Moreover, the role of the cell on the film structure and properties has been investigated. The results of the work showed that WP-based films were able to ensure a high viability of the bacteriocin-producing strain L. curvatus 54M16 during 28 days of storage at 4 �C. The addition of nutrient in the film matrix slightly affected the viability of the cells, but it was critical for the antimicrobial activity of the films. Films in presence of nutrient showed a good antimicrobial activity against L. innocua C6 as in vitro system as on cooked ham. The presence of LAB has a significant effect on the structure of the film: it reduced the viscosity of the film forming solution and improved the elasticity and the percentage of elongation. Whereas, no effect was observed for water vapour transmission rate and solubility. Thus, WP-based films in presence of modified MRS broth can be used as effective delivery and carrier systems for lactic acid bacteria to develop bioactive edible film or coating with antimicrobial properties

Linking bacterial and eukaryotic microbiota to litter chemistry: Combining next generation sequencing with 13 C CPMAS NMR spectroscopy

Microbial succession over decomposing litter is controlled by biotic interactions, dispersal limitation, grazing pressure, and substrate chemical changes. Recent evidence suggests that the changes in litter chemistry and microbiome during decomposition are interdependent. However, most previous studies separately addressed the microbial successional dynamics or the molecular changes of decomposing litter. Here, we combined litter chemical characterization by 13 C NMR spectroscopy with next generation sequencing to compare leaf litter chemistry and microbiome dynamics using 30 litter types, either fresh or decomposed for 30 and 180 days. We observed a decrease of cellulose and C/N ratio during decomposition, while lignin content and lignin/N ratio showed the opposite pattern. 13 C NMR revealed significant chemical changes as microbial decomposition was proceeding, with a decrease in O-alkyl C and an increase in alkyl C and methoxyl C relative abundances. Overall, bacterial and eukaryotic taxonomical richness increased with litter age. Among Bacteria, Proteobacteria dominated all undecomposed litters but this group was progressively replaced by members of Actinobacteria, Bacteroidetes, and Firmicutes. Nitrogen-fixing genera such as Beijerinckia and Rhizobium occurred both in undecomposed as well as in aged litters. Among Eukarya, fungi belonging to the Ascomycota phylum were dominant in undecomposed litter with the typical phyllospheric genus Aureobasidium. In aged litters, phyllospheric species were replaced by zygomycetes and other ascomycetous and basidiomycetous fungi. Our analysis of decomposing litter highlighted an unprecedented, widespread occurrence of protists belonging to the Amebozoa and Cercozoa. Correlation network analysis showed that microbial communities are non-randomly structured, showing strikingly distinct composition in relation to litter chemistry. Our data demonstrate that the importance of litter chemistry in shaping microbial community structure increased during the decomposition process, being of little importance for freshly fallen leaves

Microencapsulation of Lactobacillus reuteri DSM 17938 Cells Coated in Alginate Beads with Chitosan by Spray Drying to Use as a Probiotic Cell in a Chocolate Soufflé

The main objective of this work was to obtain microencapsulated probiotic cells in order to improve their resistance to heat stress and gastrointestinal conditions. A further aim was to obtain a potentially probiotic chocolate soufflé. Lactobacillus reuteri DSM 17938 cells were microencapsulated by spray drying in alginate matrix and further coated with chitosan. Bacterial survival after exposure to different heat treatments and simulated gastrointestinal conditions were measured to test the microcapsules. They were also dyed by using a LIVE/DEAD® BacLight™ Bacterial Viability Kit and characterized by epifluorescence microscope observation. Furthermore, a potentially chocolate soufflé was prepared using microencapsulated cells. The results indicated that alginate microcapsules did not improve acid tolerance or heat resistance in “in vitro” experiments, while they were able to protect 7% of the Lactobacillus reuteri population during the baking of a chocolate soufflé, compared to a survival rate of 1% of free cells. By contrast, the cells microencapsulated with alginate coated with chitosan showed, compared to free cells, improved acid tolerance, allowing the cell population to remain constant after 3 h in simulated gastric conditions. Moreover, the heat resistance of cells in co-cross-linked microcapsules significantly improved compared to free cells, both in “in vitro” and “in food” experiments. Microencapsulation led to a survival rate of 10% after baking a chocolate soufflé. However, the final level of bacterial cells in the product was too low to consider the chocolate soufflé as a probiotic product

Monitoring the mycobiota during Greco di Tufo and Aglianico wine fermentation by 18S rRNA gene sequencing

Spontaneous alcoholic fermentation of grape must is a complex process, carried out by indigenous yeast populations arising from the vineyard or the winery environment and therefore representing an autochthonous microbial terroir of the production area. Microbial diversity at species and biotype level is extremely important in order to develop the composite and typical flavour profile of DOCG (Appellation of Controlled and Guaranteed Origin) wines. In this study, we monitored fungal populations involved in spontaneous fermentations of Aglianico and Greco di Tufo grape must by high-throughput sequencing (HTS) of 18S rRNA gene amplicons. We firstly proposed an alternative/addition to ITS as target gene in HTS studies and highlighted consistency between the culture-dependent and -independent approaches. A complex mycobiota was found at the beginning of the fermentation, mainly characterized by non-Saccharomyces yeasts and several moulds, with differences between the two types of grapes. Moreover, Interdelta patterns revealed a succession of several Saccharomyces cerevisiae biotypes and a high genetic diversity within this species