Journal: American Journal of Enology and Viticulture

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American Society for Enology and Viticulture

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ISSN

0002-9254

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2005 - 200912010 - 20164
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Publications 1 - 5 of 5
  • Impact of the [GAR+] Prion on Fermentation and Bacterial Community Composition with Saccharomyces cerevisiae UCD932
    Item type: Journal Article
    Walker, Gordon A.; Hjelmeland, Anna; Bokulich, Nicholas; et al. (2016)
    American Journal of Enology and Viticulture
    The efficiency and efficacy of alcoholic fermentation by yeast is crucial for the winemaking process. Sluggish or arrested fermentations can negatively affect winery operations and wine quality. Here, we present a novel mechanism by which problem fermentations can arise. Yeast can induce a prion known as [GAR+] that allows the cell to circumvent glucose repression of alternative carbon substrates. We have confirmed that Saccharomyces cerevisiae strain UCD932 can spontaneously generate the [GAR+] phenotype and that this phenotype exhibits the genetic traits of a prion. Differences were observed in the fermentative behavior of UCD932 wild-type [gar−] versus [GAR+] yeasts in laboratory-scale model juice fermentations. To further understand these differences, fermentations were performed in Chardonnay juice to study the interaction of the [GAR+] prion and presence of sulfur dioxide (SO2) on fermentation kinetics, bacterial community composition, and volatile compound production. Cells harboring the [GAR+] prion displayed reduced fermentation capacity, which was especially evident in the absence of SO2. Presence of SO2 and fermentation time had the most significant effects on the types of bacteria present in the fermentation. However, [GAR+] yeasts without added SO2 were especially sensitive to bacterial competition. This difference was also reflected in the bacterial and volatile profiles of the finished wine. We hypothesize that the bacterial induction of the [GAR+] prion by yeast during fermentation is another possible mechanism by which stuck or sluggish fermentations may become established. © 2016 American Society for Enology and Viticulture.
  • Sulfur Dioxide Treatment Alters Wine Microbial Diversity and Fermentation Progression in a Dose-Dependent Fashion
    Item type: Journal Article
    Bokulich, Nicholas; Swadener, Michael; Sakamoto, Koichi; et al. (2015)
    American Journal of Enology and Viticulture
    The use of sulfur dioxide (SO2) as an antimicrobial in winemaking is a well-established, common practice. Although much is known about the antimicrobial effects of SO2 at single concentrations, little is known about its effects on microbial growth dynamics across a range of concentrations or when used in conjunction with yeast inoculation. Using high-throughput marker-gene sequencing, we investigated the cumulative impacts of yeast inoculation and SO2 treatments across a broad concentration range (0 to 150 mg/L SO2) on the bacterial and fungal communities in wine fermentations. Our results indicated a dose-dependent effect of SO2, with lactic acid bacteria and Gluconobacter proliferating in fermentations with <25 mg/L SO2, but other bacteria and fungi were unaffected by the SO2 addition. Microbial profiles stabilized at concentrations ≥25 mg/L SO2, and fermentation performance decreased at higher concentrations (100 to 150 mg/L SO2). Yeast inoculation alone conferred a stabilizing effect, reducing the bacterial growth observed in unsulfited fermentations, but this effect was not additive with an increase in SO2 concentrations. © 2015 American Society for Enology and Viticulture.
  • Profiling the yeast communities of wine fermentations using terminal restriction fragment length polymorphism analysis
    Item type: Journal Article
    Bokulich, Nicholas; Hwang, Chin-Feng; Liu, Shuwen; et al. (2012)
    American Journal of Enology and Viticulture
    Terminal restriction fragment length polymorphism (TRFLP), used most often to describe bacterial communities, presents a high-throughput, low-cost solution for analyzing mixed yeast communities in wine and other fermentations. In this study, a TRFLP approach was developed for the identification and discrimination of yeasts and used to construct a TRFLP database comprising 121 strains of yeast (representing 24 genera and 72 species) associated with wine and food fermentations. This database exhibits sensitive discrimination among species and robust intraspecific conservation of TRFLP profiles, enabling reliable characterization of mixed yeast communities. The yeast ecology of sweet, botrytized wine fermentations from two separate vintages was analyzed using this database, demonstrating the utility of this method for fast-paced, qualitative detection and identification of differences in yeast community structures over time in a complex, diverse fermentation system. © 2012 American Society for Enology and Viticulture.
  • 3-Mercaptohexanol
    Item type: Journal Article
    Fretz, Claudia Barbara; Luisier, Jean-Luc; Tominaga, Takatoshi; et al. (2005)
    American Journal of Enology and Viticulture
  • Microbial Terroir of Wine: Deep Insight into Site-Specific Winery and Vineyard Microbial Communities
    Item type: Other Conference Item
    Bokulich, Nicholas; Mills, David A. (2012)
    American Journal of Enology and Viticulture
Publications 1 - 5 of 5