Genome comparison and physiological characterization of eight Streptococcus thermophilus strains isolated from Italian dairy products

Eight Streptococcus thermophilus strains of dairy origin isolated in Italy were chosen to investigate autochthonous bacterial diversity in this important technological species. In the present study a comparative analysis of all the 17 S. thermophilus genomes publicly available was performed to identify the core and the variable genes, which vary among strains from 196 to 265. Additionally, correlation between the isolation site and the genetic distance was investigated at genomic level. Results highlight that the phylogenetic reconstruction differs from the geographical strain distribution. Moreover, strain M17PTZA496 has a genome of 2.15 Mbp, notably larger than that of the others, determined by lateral gene transfer (including phage-mediated incorporation) and duplication events. Important technological characters, such as growth kinetics, bacteriocin production, acidification kinetics and surface adhesion capability were studied in all the Italian strains. Results indicate a wide range of variability in adhesion properties that significantly clustered strains into four groups. Genomic differences among strains in relation to these characters were identified but a clear correlation between genotype and phenotype was not always found since most of the genomic modifications arise from single nucleotide polymorphisms. This research represents a step forward in the identification of strains-specific functions in Streptococcus thermophilus and it has also the potential to provide valuable information to predict strain specific behaviors in industrial processes

The role of nitrogen uptake on the competition ability of three vineyard Saccharomyces cerevisiae strains

Three vineyard strains of Saccharomyces cerevisiae, P301.4, P304.4 and P254.12, were assayed in comparison with a commercial industrial strain, QA23. The aim was to understand if nitrogen availability could influence strain competition ability during must fermentation. Pairwise-strain fermentations and co-fermentations with the simultaneous presence of the four strains were performed in synthetic musts at two nitrogen levels: control nitrogen condition (CNC) that assured the suitable assimilable nitrogen amount required by the yeast strains to complete the fermentation and low nitrogen condition (LNC) where nitrogen is present at very low level. Results suggested a strong involvement of nitrogen availability, as the frequency in must of the vineyard strains, respect to QA23, in LNC was always higher than that found in CNC. Moreover, in CNC only strain P304.4 reached the same strain frequency as QA23. P304.4 competition ability increased during the fermentation, indicating better performance when nitrogen availability was dropping down. P301.4 was the only strain sensitive to QA23 killer toxin. In CNC, when it was co-inoculated with the industrial strain QA23, P301.4 was never detected. In LNC, P301.4 after 12 h accounted for 10% of the total population. This percentage increased after 48 h (20%). Single-strain fermentations were also run in both conditions and the nitrogen metabolism further analyzed. Fermentation kinetics, ammonium and amino-acid consumptions and the expression of genes under nitrogen catabolite repression evidenced that vineyard yeasts, and particularly strain P304.4, had higher nitrogen assimilation rate than the commercial control. In conclusion, the high nitrogen assimilation rate seems to be an additional strategy that allowed vineyard yeasts successful competition during the growth in grape musts

Co-fermentation of onion and whey: a promising synbiotic combination

Juice from three different onion varieties was mixed with sweet whey and used as growth 18 substrate for four lactic acid bacteria strains, isolated from agri-food by-products, to 19 evaluate the possibility to exploit such substrates, known to be reach in bioactive 20 molecules, as fermented drinks for human consumption. Results show good growth 21 performance for Lactobacillus fabifermentans, L. plantarum and Streptococcus 22 macedonicus. On the contrary S. thermophilus did not grow in the mixture while S. 23 macedonicus did not develop in pure onion juice. After 48 h the overall sugar content 24 decreased significantly. In particular, glucose was not utilized while inulin was completely 25 preserved. Moreover, MS/MS analysis revealed the presence of the rare trisaccharide 26 lactosucrose. 27 In the light of these considerations, the formulation obtained may be considered a potential 28 synbiotic product with pleasant taste and beneficial effects for consumers and also an eco-29 friendly solution to convert an agro-food by-product into value added products

Biocontrol Ability and Action Mechanism of Starmerella bacillaris (Synonym Candida zemplinina) Isolated from Wine Musts against Gray Mold Disease Agent Botrytis cinerea on Grape and Their Effects on Alcoholic Fermentation

Gray mold is one of the most important diseases of grapevine in temperate climates. This plant pathogen affects plant growth and reduces wine quality. The use of yeasts as biocontrol agents to apply in the vineyard have been investigated in recent years as an alternative to agrochemicals. In this work, fermenting musts obtained from overripe grape berries, therefore more susceptible to infection by fungal pathogens such as Botrytis cinerea, were considered for the selection of yeasts carrying antifungal activity. Thirty-six isolates were identified as Starmerella bacillaris, a species recently proven to be of enological interest. Among them 14 different strains were studied and antifungal activity against B. cinerea was demonstrated, for the first time, to be present in S. bacillaris species. The production of volatile organic compounds (VOCs), tested in vitro, was found to be the main responsible of S. bacillaris antifungal effects. All the strains were able to reduce B. cinerea decay on wounded grape berries artificially inoculated with gray mold. The colonization level of wound was very high reaching, after 5 days, a concentration of 10(6) cells per ml of grape juice obtained after berry crushing. At this cell concentration S. bacillaris strains were used to ferment synthetic and natural musts. The sequential yeast inoculation, performed by adding S. cerevisiae 48 h after S. bacillaris, was needed to complete sugar consumption and determined a significant increase in glicerol content and a reduction of ethanol and acetic acid concentrations. The high wound colonization ability, found in this work, together with the propensity to colonize grape berry and the interesting enological traits possessed by the selected S. bacillaris strains allow the use of this yeast as biocontrol agent on vine and grape berries with possible positive effects on must fermentation, although the presence of S. cerevisiae is needed to complete the fermentation process. This work introduces new possibilities in wine yeast selection programs in order to identify innovative wine yeasts that are simultaneously antifungal agents in vineyards and alternative wine starters for grape must fermentation and open new perspective to a more integrated strategy for increasing wine quality

The addition of wine yeast Starmerella bacillaris to grape skin surface influences must fermentation and glycerol production

Starmerella bacillaris is a non-Saccharomyces yeast recently proposed for grape fermentation in association with Saccharomyces cerevisiae. Due to its high glycerol and moderate volatile acidity production this yeast can contribute to improving wine quality. Some strains have been demonstrated to exhibit antifungal activity against grey mould on grape, which is caused by Botrytis cinerea. The simultaneous presence of these traits in S. bacillaris is of great interest. Indeed, this yeast can be potentially used as a biocontrol agent in vineyards. Research on the ability of S. bacillaris to survive or, even to grow on the surface of grapes is a starting point in the evaluatation of its potential use in vineyards. The preliminary results of our study showed that when applied to the grape surface under laboratory condictions, inoculum sized S. bacillaris with antifungal activity developed and lasted for at least 6 days in high concentrations. In addition, it positively influenced the fermentation process by producing high concentrations of glycerol (average value 4.89 ± 0.47 g/L). Interestingly, a positive effect on wine quality was also observed when the inoculum size was 10 times higher or lower than the reference concentration. When sprayed on the vines in the vineyard and present on the grape skin surface after harvest, S. bacillaris cells can start alcoholic fermentation

Characteristics of Compost Obtained from Winemaking Byproducts

A model procedure for the sustainable management of plant biomass related to wine production, namely vine branches from agricultural practices in the vineyard and marcs remaining after grapes crushing, was devised. An artificial humification process was set up that could respond to the needs of environmental sustainability and could be a safe way to be reintroduce in the vineyard part of the organic matter previously exported, thus contributing to recover or maintain vineyard soil fertility. Two different strategies for composting were tested, namely a static pile, made by branches and marcs, and a pile that was fed twice a year alternatively with vine branches and grape marcs. The experimentation lasted 710 days, during which environmental parameters, i.e. temperature and rainfalls were monitored. Growth dynamics of the principal functional groups of microorganism were followed. A characterization of the composted material was obtained by measuring several parameters among which, pH, carbon, nitrogen, sulfur and heavy metals content. The characteristics of the produced compost fulfill the requirements prescribed by the Italian legislation regarding the use of compost as soil amendment. Germination tests demonstrated the absence of phytotoxicity and conversely evidenced a stimulating activity towards root development

Genome Sequences of Four Italian Streptococcus thermophilus Strains of Dairy Origin.

This report describes the genome sequences of four Streptococcus thermophilus strains, namely, TH982, TH985, TH1477, and 1F8CT, isolated from different dairy environments from the Campania and the Veneto regions in Italy. These data are aimed at increasing the genomic information available on this species, which is of paramount importance for the dairy industry

Antiradical and antimicrobial properties of fermented red chicory (Cichorium intybus L.) by-products

Discarded leaves of red chicory (Radicchio \u201cRosso di Chioggia\u201d IGP) were fermented with one Saccharomyces yeast and four lactic acid bacteria chosen on the basis of their ability to grow on plant material without any need of supplements. Antiradical and antimicrobial activities of the resulting products were assessed. Among the strains tested, Lactobacillus plantarum and L. hilgardii gave the best performances and also provided fermented substrates with antiradical and antimicrobial activities. In particular the latter compounds were found only in fermented samples, confirming that the choice of appropriate microorganisms for fermentation could be useful when the aim is to target specific functional foods starting from by-products or waste material

Genome Sequences of Streptococcus thermophilus Strains MTH17CL396 and M17PTZA496 from Fontina, an Italian PDO Cheese.

Here is presented the whole-genome sequences of Streptococcus thermophilus strains MTH17CL396 and M17PTZA496, isolated from fontina protected designation of origin (PDO) cheese in the Valle d\u2019Aosta Region (Italy). S. thermophilus is a lactic acid bacterium widely present in dairy products, and these are the first publicly available genome sequences of S. thermophilus strains isolated from cheese