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Whey valorisation by microbial fermentation
Full text linkStreptococcus thermophilus is a thermophilic lactic acid bacterium (LAB) of major importance in the dairy industry. This species is widely used as starter culture to produce fermented dairy products. It has been awarded the status of GRAS (Generally Recognized as Safe) in the USA and a Qualified Presumption of Safety (QPS) status in the European Union, due to its long history of safe use in food production. Increasing the number of starter available to producers by discovering new strains with desirable characters is important not only for identifying new properties that may better suited the needs of the industrial raising demand but also to preserve natural biodiversity, which is diminishing with the spread and overuse of commercial starters.
The progresses in high-throughput ‘omics’ technologies (‘Foodomics’) allows the development of more rational approaches aimed to improve fermentation processes both for the traditional foods productions and for new functional food products . Nevertheless, to date only few steps were made toward the in-depht analysis of the pan-genome and transcriptional regulation in species of food interest.
In this study the whole genome sequencing of eight S. thermophilus strains isolated from typical cheese-making processes in four Italian regions was performed using the Illumina platform. Genomic data were compared with the already available information in order to study the level of genetic biodiversity present within the species. In addition, some technological properties were analysed both genetically and phenotypically to integrate the knowledges at these two levels.
The applicative part of the study regarded the study of the strains during growth on milk whey, both from physiological and genetic (gene expression) standpoints. Particular effort was dedicated to production of vitamin, in particular folates. The obtained results, reported in this thesis, are interesting both from a scientific and applicative point of view.Streptococcus thermophilus appartiene ai batteri lattici (LAB) termofili ed è un microrganismo di primaria importanza nel settore caseario. Questa specie è largamente usata come starter nella produzione di prodotti caseari fermentati. Grazie alla sua lunga storia nella produzione di alimenti, gli è stato conferito lo stato di GRAS (Generally Recognized as Safe) negli Stati Uniti d’America e di QPS (Qualified Presumption of Safety) nell’Unione Europea. Aumentare il numero di ceppi starter disponibili per i produttori caseari, scoprendo ceppi autoctoni che posseggano caratteri tecnologicamente rilevanti, è importante non solo per identificare nuove proprietà che possano rispondere maggiormente alla crescente domanda, ma anche per preservare la naturale biodiversità che sta diminuendo con il diffondere e il sempre maggiore degli starter commerciali.
I progressi attuali nelle tecnologie high throughput (‘Foodomics’) permettono lo sviluppo di approcci razionali per l’ottimizzazione del processo fermentativo sia nella tradizionale funzionalità alimentare sia nella nuova potenzialità dei prodotti nutraceutici. Tuttavia, non molti passi sono stati fatti verso l’analisi dettagliata della pan-genomica e della regolazione trascrizionale nelle specie di interesse alimentare.
In questo studio, è stato portato a termine il sequenziamento completo del genoma di otto ceppi di S. themophilus isolati da processi di caseificazione tradizionali in varie località italiane. I dati genomici sono stati comparati con l’informazione disponibile nei database pubblici nel tentativo di studiare il livello di biodiversità genetica presente all’interno della specie. Inoltre, alcune proprietà tecnologicamente rilevanti sono state analizzate sia geneticamente sia fenotipicamente in modo da integrare le conoscenze a questi due livelli
La parte applicativa dello studio ha riguardato lo studio dei ceppi durante la crescita in siero di latte, sia dal punto di vista fenotipico che dell’espressione genica, con particolare attenzione alla produzione di vitamine e specificamente di folati. I risultati ottenuti hanno prodotto informazioni interessanti sia dal punto di vista scientifico che, in prospettiva, da quello applicativo
La genomica dei batteri lattici: quali benefici per il settore caseario? Un caso studio: Streptococcus thermophilus
No full textGenome Sequences of Streptococcus thermophilus Strains MTH17CL396 and M17PTZA496 from Fontina, an Italian PDO Cheese.
Full text linkHere 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'Aosta 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
Whole-Genome Sequence of Streptococcus macedonicus Strain 33MO, Isolated from the Curd of Morlacco Cheese in the Veneto Region (Italy).
Full text linkA genetic characterization of Streptococcus macedonicus is important to better understand the characteristics of this lactic acid bacterium, frequently detected in fermented food bacteria communities. This report presents the draft genome sequence description of strain 33MO, the first publicly available genome sequence of an Italian S. macedonicus isolate
Genome comparison and physiological characterization of eight Streptococcus thermophilus strains isolated from Italian dairy products
Full text linkEight 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
Whole genome sequences of Streptococcus thermophilus strains TH1435 and TH1436 isolated from raw goat milk
No full textWe report the genome sequences of two Streptococcus thermophilus strains, TH1435 and TH1436, isolated from raw goat milk devoted to the production of artisanal cheese in the Friuli-Venezia Giulia region in Italy. The genome sequences of these two quickly acidifying strains are the first available genome sequences of S. thermophilus strains isolated in Italy
Valorization of scotta, the by-product of ricotta production, by microbial fermentation for production of a probiotic drink
No full textRicotta is a typical Italian dairy product obtained after thermal treatment of whey, which determines the coagulation of the whey proteins. The scotta (ricotta cheese whey) is the liquid waste remaining at the end of the process and in Italy this by-product accounts for about 345.000 t each year.
Some studies have been conducted so far on its use for bioenergy production. Differently, we explored the potentiality of scotta for food use, in particular for the production of a fermented drink, which could represent a valuable opportunity for the use of the scotta inside the cheese factory.
We first collected and characterized several scotta (acid scotta and sweet scotta) from five cheese factories in the Veneto region, which represents the third cheese producing region of Italy. Analyses were conducted to gain information on chemical (lactose, proteins) and microbiological (total counts, main bacterial groups) characteristics.
We then evaluated the effect of a thermal treatment as a means to reduce the microbial load without negatively impacting on chemical characteristics.
We chose some lactic acid bacteria, either starter, namely Streptococcus thermophilus and Lactobacillus delbrueckii subsp. bulgaricus, and non-starter strains, i.e. Lactobacillus casei, Lactobacillus rhamnosus, Lactobacillus johnsonii and Lactobacillus acidophilus, all isolated from commercial dairy products, and evaluated their capability to efficiently develop in Scotta. In addition we also performed some co-inoculations of couples of strains.
Results evidence a good to very-good capability of the strains to growth on scotta (up to 109 cfu/ml) and to lower the pH (between 5.4 and 3.8).
These results highlight the potential of scotta to be used as substrate for LAB fermentations, which is the first step towards the production of a possible probiotic drink by microbial fermentation of scotta
Potential use of scotta, the by-product of the ricotta cheese manufacturing process, for the production of fermented drinks
No full textIn the present work, the use of scotta as substrate for bacterial fermentation was studied with the objective of obtaining a drink from transformation of this by-product. Scotta retains most of the lactose of the milk and it is normally colonized by a natural microbiota. A treatment was devised to reduce the autochthonous microbial populations in order to reduce competition towards the inoculated bacterial strains. Nine lactic acid bacteria (LAB) were assessed for their capability to develop in scotta. They evidenced different behaviors regarding growth rate, acidification capability and nitrogen consumption. A co-inoculum of three LAB, namely a Streptococcus thermophilus, a Lactobacillus delbrueckii subsp. bulgaricus and a Lb. acidophilus strains, chosen among those giving the best performances in single-strain fermentation trials, gave abundant (close to 109 cfu/ml) and balanced growth and lowered pH to 4·2, a value similar to that of yogurt. These results show that scotta may have potential as a substrate for bacterial growth for the production of a fermented drink. Further studies are needed to optimize the organoleptic aspects of the final product
Genome Sequences of Four Italian Streptococcus thermophilus Strains of Dairy Origin.
Full text linkThis 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
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