1,721,070 research outputs found
Mitochondrial inheritance in budding yeasts: towards an integrated understanding.
No full textRecent advances in yeast mitogenomics have significantly contributed to our understanding of the diversity of organization, structure and topology in the mitochondrial genome of budding yeasts. In parallel, new insights on mitochondrial DNA (mtDNA) inheritance in the model organism Saccharomyces cerevisiae highlighted an integrated scenario where recombination, replication and segregation of mtDNA are intricately linked to mitochondrial nucleoid (mt-nucleoid) structure and organelle sorting. In addition to this, recent discoveries of bifunctional roles of some mitochondrial proteins have interesting implications on mito-nuclear genome interactions and the relationship between mtDNA inheritance, yeast fitness and speciation. This review summarizes the current knowledge on yeast mitogenomics, mtDNA inheritance with regard to mt-nucleoid structure and organelle dynamics, and mito-nuclear genome interactions
I lieviti ibridi nell'era dell'ingegneria genetica
No full textBreeding fra specie o fra ceppi diversi di Saccharomycescerevisiae rappresenta una delle prime strategie di miglioramento genico applicate ai lieviti.La combinazione di tecniche classiche e di tecnologie whole genome, come i DNA microarray, possonoessere integrate con successo per contribuire all’analisidelle basi genetiche e funzionali dei caratteri fenotipici complessi e per incrementare il controllo neiprocessi di costituzione di lieviti di interesse enologic
Yeasts associated to Traditional Balsamic Vinegar: Ecological and technological features
No full textTraditional Balsamic Vinegar (TBV) is an Italian homemade vinegar made with cooked grape must through a three-step process: conversion of sugars to ethanol by naturally occurring yeasts; oxidation of ethanol to acetic acid by acetic acid bacteria (AAB); and, finally, at least 12-years ageing. The cooked must is a selective and stressful medium for yeasts growth, due to its high sugar content and low pH values. Recent studies have shown that a large number of yeast species are involved in the fermentation, among them there are Zygosaccharomyces bailii, Zygosaccharomyces rouxii, Zygosaccharomyces pseudorouxii, Zygosaccharomyces mellis, Zygosaccharomyces bisporus, Zygosaccharomyces lentus, Hanseniaspora valbyensis, Hanseniaspora osmophila, Candida lactis-condensi, Candida stellata, Saccharomycodes ludwigii and Saccharomyces cerevisiae. Nevertheless, the TBV-associated yeast population could be even more complex and many other slow-growing or poorly cultivable species might contribute to cooked must fermentation. In this review the main TBV yeast species are described, pointing out their role in TBV production and their influence on final product quality. Finally, both future developments in TBV yeast community studies (culture-independent and metagenomic techniques) and technological advances in TBV making (use of starter culture) are discussed
Lieviti starter per aceto balsamico tradizionale.
No full textLa fermentazione alcolica del mosto cottorappresenta la prima fase microbiologica nellaproduzione di ABT (Aceto Balsamico Tradizionale).La popolazione di lieviti che conducono questoprocesso fermentativo influenza direttamente eindirettamente le proprietà organolettiche delprodotto finale, nonché le sue caratteristichemacroscopiche. La fermentazione spontanea delmosto cotto è un processo incontrollato e nonprogrammabile, che spesso si interrompe senzache venga prodotta una quantità sufficiente dietanolo per consentire la successiva ossidazioneacetica. La disponibilità di colture di lievito starterper ABT risolverebbe queste problematichema la loro messa a punto è imprescindibile dalsoddisfacimento di tre presupposti: lo studioapprofondito della microflora dell’ABT; lacostituzione di un patrimonio genetico medianteselezione clonale; la definizione dei caratterispecifici che una coltura starter per ABT devepossedere. Nel presente lavoro definiamo iprincipali caratteri di fitness e di qualità che,sulla base delle conoscenze attuali, un lievitoselezionato per ABT deve possedere e descriviamoper le principali specie di lievito riscontratenell’ABT, il loro comportamento relativo ad alcunidi questi caratteri. Infine prendiamo in esame lepossibilità offerte dalle tecniche di miglioramentogenetico per la combinazione di caratteridesiderati
Determinazione dei batteri lattici nel vino mediante tecniche coltura-indipendenti.
No full textNel presente studio abbiamo utilizzato una tecnica coltura-indipendente, laPCR-DGGE, per il monitoraggio della popolazione microbica in campioni divino inoculati con differenti starter lattici di Oenococcus oeni. La PCR-DGGEapplicata direttamente alla matrice vino ha messo in evidenza come lo starterOenococcus oeni fosse la specie dominante in tutti i campioni esaminati
Vinegars of the World
No full textThe story of microbial biotransformation is closely associated with vinegar production, which dates back to around 2000 years BC. However, among fermented foods, vinegar has been always considered a “poor” component: it is not a “food”, it doesn’t have high nutritional values, and it is produced by transformation of other more nutritive rich fermented foods. Vinegar is a condiment, but also a preservative and, in some countries, a healthy drink. It can be made by a two step fermentation of yeasts followed by acetic acid bacteria from almost any fermentable carbohydrate source: apples, pears, grapes, honey, syrups, cereals, hydrolysed starches, beer, and wine are all ideal substrates for the production of vinegar. Since vinegars is, with few exceptions, an inexpensive commodity, its production requires a low-cost raw material, such as sub-standard fruits, seasonal agricultural surpluses, various food processing by-products and fruit waste. However there are vinegars, so called spirit vinegars, obtained directly by acetic oxidation of alcohol obtained from distillation of fermented mashes or, in some countries, petrolchemical ethanol. Some western by-products of wood carbonization obtained by distillation of pyroligneous liquor collected during wood pyrolisis, are called “vinegar” and they are used as agricultural material, animal health product, cosmetic ingredients and folk drug in Japan and Est-Asia (Mu et al., 2003; Mu et al., 2006). These distilled solutions have not be considered as vinegar because no fermentative process occurs in their production. Other specialty vinegars are grouped as herbal or fruit vinegars. In this cases the name “X vinegar” doesn’t indicate the raw materials used in vinegar fermentation but the flavours added to obtain specific taste and characteristic sensorial features. Herbal vinegars consist of wine vinegars or white distilled vinegars, which may be seasoned with garlic, basil, tarragon, cinnamon, clove, or nutmeg. Fruit-flavoured vinegars are wine and white vinegars sweetened with fruit or fruit juice to produce a characteristic sweet-sour taste. Traditional vinegars are very expensive vinegar produced from regional foods according to well-established customs: balsamic vinegar of Modena from Italy; Sherry vinegar from Spain; Champagne vinegar from France etc. According to international definition of vinegar, in this book we considered only vinegar derived from a two stage fermentation process. However with many of the vinegars in Africa, Asia and Latin America, knowledge of the processes involved is poor and a comprehensive view of all different kinds of vinegars is impossible. Therefore it is likely that the worldspread vinegars give a very greater picture. Economy, technology and law about vinegar were described in this chapter
Strategy for yeast improvement
No full textSelection and genetic improvement of yeast starter cultures are based on the ability to achieve a specific task or to perform a precise function. The process can be summarized into few steps: i) the knowledge of yeast microbiota in a specific ecological niche to yield species suitable to grow on specific substrates; ii) clonal selection for obtaining a wide genetic background; iii) definition of desired traits for yeast selection. However the selection of wild strains having complete combination of all traits is not so easy to obtain. There are many strategies for improving yeasts and increasing the recombination of all desired traits within an unique genome. The choice of most suitable strategy is mainly based on three factors: the genetic nature of traits (monogenic or polygenic), the knowledge of the genes involved, the aim of the genetic manipulation.Recent developments in genetic dissection of yeast quantitative traits highlighted how the several interesting traits can be complex and influenced by several genes. In a context of low phenotype-genotype correlation, both the rational approach involving DNA recombinant technologies and the traditional random techniques based on mutagenesis meet serious obstacles. Otherwise, different blind strategies, involving the cell entire genome, can be applied in order to obtain quickly strains with interesting recombinant traits. Laboratory sexual hybridization and genome shuffling are accelerated evolutionary approaches that allow to obtain desired complex phenotypes more rapidly than any normal rational methods
Impact of non-starter lactobacilli on release of peptides with angiotensin-converting enzyme inhibitory and antioxidant activities during bovine milk fermentation
No full textThis study aimed at evaluating non-starter lactobacilli (NSLAB) isolated from cheeses for their proteolytic activity and capability to produce fermented milk enriched in angiotensin-converting enzyme (ACE)-inhibitory and antioxidant peptides. Preliminarily, 34 NSLAB from Parmigiano Reggiano (PR) and 5 from Pecorino Siciliano cheeses were screened based on their capacity to hydrolyze milk proteins. Two NSLAB strains from PR, Lactobacillus casei PRA205 and Lactobacillus rhamnosus PRA331, showed the most proteolytic phenotype and were positively selected to inoculate sterile cow milk. The fermentation process was monitored by measuring viable cell population, kinetic of acidification, consumption of lactose, and
synthesis of lactic acid. Milk fermented with Lb. casei PRA205 exhibited higher radical scavenging (1184.83 ± 40.28 umol/L trolox equivalents) and stronger ACE-inhibitory (IC50 = 54.57 ug/mL) activities than milk fermented with Lb. rhamnosus PRA331 (939.22 ± 82.68 umol/L trolox equivalents;
IC50 = 212.38 ug/mL). Similarly, Lb. casei PRA205 showed the highest production of ACE-inhibitory peptides Val-Pro-Pro and Ile-Pro-Pro, which reached concentrations of 32.88 and 7.52 mg/L after 87 and 96 h of milk fermentation, respectively. This evidence supports Lb. casei PRA205, previously
demonstrated to possess characteristics compatible with probiotic properties, as a promising functional culture able to promote health benefits in dairy food
No-culture strategy for tracking AAB and yeasts in low-acidic and high polyphenolic niches
No full textCommunity of acetic acid bacteria (AAB) and yeasts inhabitslow acidic and high polyphenolic niches such as fermentedbeverages. In this work, we selected kombucha asmodel to optimize a no-culture strategy for tracking thedynamics of AAB and yeasts. The strategy consisted of: i)Genomic DNA extraction optimization, ii) PCR/DGGEsetup and iii) Validation of the assay. For gDNA extractionoptimization, we evaluated the suitability of the followinggDNA preparations for a standard PCR-DGGE assay: 1)CTAB/AAB; 2) CTAB/vinegar; 3) Freeze/bead/CTAB1; 4)Freeze/bead/CTAB2 methods. Different extraction methodsaffected not only the quantity and purity of DNA but alsothe complexity of PCR/DGGE profiling. Method 4 allowedus to obtain suitable DNA for PCR assays, as well as thehighest level of complexity in PCR/DGGE band patternsboth for AAB and yeasts. Moreover changes from exopolysaccharidicto liquid phases did not affect the suitability ofthis method. PCR/DGGE setup was performed consideringthe following variables: DNA template concentration, PCRconditions and specificity, effect of GC-clamp and nestedPCR. For AAB, primers pair WBAC1/WBAC2 enabled tostudy AAB dynamics as well other bacterial groups, whereas341f/518r permitted the detection of members of theGluconacetobacter genus. For yeasts, primers pair U1/U2was more efficient then NL1/LS2 in community profiling ofthe majority of kombucha samples. GC-clamp added toforward primers negatively affected gDNA suitability and anested re-PCR for yeasts and AAB was required. Finally,validation of the assay was carried out during kombuchafermentation following AAB and yeasts dynamics from theinoculum to 12 days of incubation. Within AAB species,Gluconacetobacter xylinus responsible for the exopolysaccharidicnetwork matrix, was mainly detected, whereasZygosaccharomyces spp, Dekkera spp, Pichia spp andSchizosaccharomyces pombe in the case of yeasts
LA SELEZIONE E IL MITO DEI LIEVITI AUTOCTONI
No full textLa scelta del ceppo di lievito influenza il successo della fermentazionealcolica dei vini e modula profondamente la qualità delprodotto finale. Analisi molecolari hanno portato ad una profondarevisione della tassonomia dei lieviti ed hanno facilitato gli studiecologici delle fermentazioni spontanee dei mosti, evidenziandol’esistenza della specie Saccharomyces cerevisiae in habitat naturalinon antropici. Le specie riscontrate sulle uve sono in numeroelevato e maggiore che non nei mosti e nei vini, dove esiste unaforte pressione selettiva del mezzo e delle condizioni tecnologicheimpiegate. In generale, più stringenti sono le condizioni di crescita,minore è il numero di specie in grado sviluppare. S. cerevisiae èla specie più alcool tollerante ed è per questa ragione che a finefermentazione è sempre la più rappresentata, nonostante sia pocofrequente sulle uve. Queste osservazioni hanno suggerito la tesidella domesticazione della specie S. cerevisiae e quella dei lievitiautoctoni, ma le evidenze a supporto non possono essere consideratesufficienti. In particolare, la tesi dei lieviti autoctoni è debole,specie nel passaggio che attribuisce ai lieviti autoctoni un contributosignificativo nella qualità dei vini corrispondenti. I buoniceppi di lievito sono il risultato di un programma di selezione emiglioramento genetico e, solo raramente, l’oggetto di un isolamentocasuale. In questo articolo discutiamo il significato deitermini “domesticazione” ed “autoctono” in biologia, suggerendoche il termine “autoctono” marca troppo il rapporto tra luogo,tempo e ceppo, lasciando intendere una dipendenza non dimostrata.Il termine “indigeni” è molto più appropriato per definire i lievitipresenti in un mosto, in una cantina o in un vigneto, e con esso siintendono i lieviti presenti in un determinato momento, senzapretese di continuità temporale
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