Molecular and enological characterization of autochthonous <i>Saccharomyces cerevisiae</i> strains isolated from grape-musts and wines Cannonau

Fermentation by autochthonous yeasts may produce wines with enological properties that are unique of a specific area or variety of grape must. In order to identify yeast starter strains for the production of the Sardinian wine Cannonau DOC, 66 Saccharomyces cerevisiae strains, isolated from musts and wines Cannonau of six vitivinicole areas in Sardinia, were subjected to enological characterization and molecular identification. The RFLP-PCR fingerprinting of the ITS region of rRNA (ITS1-5,8S- ITS2) as well as ethanol, foam, and H2S production were analysed

Saccharomyces and Non-Saccharomyces Starter Yeasts

This chapter describes the importance of yeast in beer fermentation. Initially, the differences between Saccharomyces cerevisiae and Saccharomyces pastorianus in the production of “ale” and “lager” beers are analyzed. Then, the relationships between beer nutrients and yeast growth are discussed, with special emphasis on the production of the flavor compounds. The impact of the wort composition on flocculation is also discussed. Furthermore, conventional approaches to starter yeast selection and the development of genetically modified microorganisms are analyzed. Recent discoveries relating to the use of S. cerevisiae strains isolated from different food matrices (i.e., bread and wine) and the potential for the use of non-Saccharomyces starter strains in beer production are discussed. A detailed review of the selection of starter strains for the production of specialty beers then follows, such as for gluten-free beers and biologically aged beers. Yeast recovery from top-cropping and bottom-cropping systems and the methodologies and issues in yeast propagation in the laboratory and brewery (i.e., re-pitching) are also analyzed. Finally, the available commercial preparations of starter yeast and the methods to evaluate yeast viability prior to inoculation of the must are analyzed

A <i>Saccharomyces cerevisiae</i> wine strain inhibits growth and decreases ochratoxin a biosynthesis by <i>Aspergillus carbonarius</i> and <i>Aspergillus ochraceus</i>

The aim of this study was to select wine yeast strains as biocontrol agents against fungal contaminants responsible for the accumulation of ochratoxin A (OTA) in grape and wine and to dissect the mechanism of OTA detoxification by a Saccharomyces cerevisiae strain (DISAABA1182), which had previously been reported to reduce OTA in a synthetic must. All of the yeast strains tested displayed an ability to inhibit the growth of Aspergillus carbonarius both in vivo and in vitro and addition of culture filtrates from the tested isolates led to complete inhibition of OTA production. S. cerevisiae DISAABA1182 was selected and further tested for its capacity to inhibit OTA production and pks (polyketide synthase) transcription in A. carbonarius and Aspergillus ochraceus in vitro. In order to dissect the mechanism of OTA detoxification, each of these two fungi was co-cultured with living yeast cells exposed to yeast crude or to autoclaved supernatant: S. cerevisiae DISAABA1182 was found to inhibit mycelial growth and OTA production in both Aspergilli when co-cultured in the OTA-inducing YES medium. Moreover, a decrease in pks transcription was observed in the presence of living cells of S. cerevisiae DISAABA1182 or its supernatant, while no effects were observed on transcription of either of the constitutively expressed calmodulin and β-tubulin genes. This suggests that transcriptional regulation of OTA biosynthetic genes takes place during the interaction between DISAABA1182 and OTA-producing Aspergilli

Selection of Saccharomyces cerevisiae Starter Strain for Merwah Wine

In order to select Saccharomyces cerevisiae starter strains for ''Merwah'' wine production, three strains (M.6.16, M.10.16, and M.4.17) previously isolated from ''Merwah'' must and characterized at the lab scale were tested in pilot-scale fermentation in a Lebanese winery during the 2019 vintage. The three inoculated musts were compared to that obtained with a spontaneous fermentation. During the fermentations, must samples were taken to evaluate the dominance of the inoculated strains, and at the end of fermentation, the obtained wines were subjected to chemical and sensorial characterization. Molecular monitoring by interdelta analysis revealed that only M.4.17 was able to complete the fermentation and dominate over the wild yeasts. Based on the analysis of principal technological parameters (i.e., residual sugar, fermentative vigor, sulfur production, and acetic acid) and sensorial analysis of the wines obtained, M.4.17 was selected as an adequate starter for the production of typical ''Merwah'' wine

Interventi tecnologici per la valorizzazione delle olive da tavola della varietà "Manna"

Sardinia table olives are chiefly obtained with the natural style, by processing green fruits. Due to lack of scientific data products are of low quality. The present study was aimed to verify the effectiveness of some technological steps, such as brine acidification and sugar or microbial starter adjunct on main chemical-physical parameters of "Manna". Results clearly show beneficial effects of starter inoculation and acidification and on the sensorial and safety standpoint. La produzione di olive da mensa in Sardegna è condotta quasi esclusivamente con il metodo al naturale su olive verdi. Tale tecnologia, vista anche la mancanza di documentazione scientifica al riguardo, porta spesso all'ottenimento di un prodotto scadente. Con il presente lavoro si è verificata l'efficacia di alcuni interventi tecnologici, quali l'acidificazione della salamoia e l'aggiunta di substrato fermentescibile o di starter microbici, sui principali parametri chimico-fisici delle olive della varietà "Manna". I risultati ottenuti evidenziano gli effetti positivi, dal punto di vista sensoriale e igienico-sanitario, dello starter e dell'acidificazione

Microbial communities and malt quality of durum wheat used in brewing

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Exploitation of the semi-homothallic life cycle of Saccharomyces cerevisiae for the development of breeding strategies.

A strain of Saccharomyces cerevisiae having desirable winemaking properties and high spore viability was bred from a semi-homothallic parent strain with similar winemaking properties but that produced sixfold fewer viable spores. Because the parent was homozygous for HO and for the MATa allele at both silent HMR and HML loci, it produced two MATa and two nonmating progeny per ascus. To obtain a segregant able to mate with the stable MATa progeny, a strain of the nonmating progeny, previously subjected to HO distruption with a KanMX4 cassette, was used. The resultant MATalphaho::KanMX4 transformant was mated to a MATa HO segregant and the diploid produced was sporulated to allow the isolation of a semi-homothallic diploid segregant designated 2D that lacked the KanMX4-disrupted HO allele as confirmed by sequence analysis. Genetic analysis indicated greater homozygosity in 2D than in the parent as assessed by PCR at five loci. The sugar consumption profiles of both 2D and the parent in grape juice fermentations were the same. Acetaldehyde levels and postfermentation biofilm formation were higher in 2D than in the parent. Because 2D has acceptable winemaking characteristics but produces significantly more viable spores than the parent strain, it will be useful in future breeding efforts

PCR-based methods to discriminate Bacillus thuringiensis strains

Bacillus thuringiensis is a Gram positive bacterium that is used for the production of biopesticides. The toxic action of different strains and serovars ofB. thuringiensis can be extremely selective towards specific pests, or, in contrast, it can affect a wide variety of non-target organisms such as insects, vertebrates or humans. A reliable characterization of the cultivated strains is of primary importance for the biopesticide industry, in order to assess the contamination of the final product with strains with different pesticide actions or that might be dangerous for human health. The aim of this study was to develop useful methods for the typing of differentB. thuringiensis strains using two PCR-based methods, RAPD and Rep-PCR with BOXA1R and ERIC2 primers. The molecular fingerprints obtained using ERIC2-PCR showed a reliable ability to discriminateBacillus thuringiensis strains

Preservation, Characterization and Exploitation of Microbial Biodiversity: The Perspective of the Italian Network of Culture Collections

Microorganisms represent most of the biodiversity of living organisms in every ecological habitat. They have profound effects on the functioning of any ecosystem, and therefore on the health of our planet and of human beings. Moreover, microorganisms are the main protagonists in food, medical and biotech industries, and have several environmental applications. Accordingly, the characterization and preservation of microbial biodiversity are essential not only for the maintenance of natural ecosystems but also for research purposes and biotechnological exploitation. In this context, culture collections (CCs) and microbial biological resource centres (mBRCs) are crucial for the safeguarding and circulation of biological resources, as well as for the progress of life sciences. This review deals with the expertise and services of CCs, in particular concerning preservation and characterization of microbial resources, by pointing to the advanced approaches applied to investigate a huge reservoir of microorganisms. Data sharing and web services as well as the tight interconnection between CCs and the biotechnological industry are highlighted. In addition, guidelines and regulations related to quality management systems (QMSs), biosafety and biosecurity issues are discussed according to the perspectives of CCs and mBRCs