Document Detail


Survival rate of wine-related yeasts during alcoholic fermentation assessed by direct live/dead staining combined with fluorescence in situ hybridization.
MedLine Citation:
PMID:  22819715     Owner:  NLM     Status:  Publisher    
Abstract/OtherAbstract:
Real-time detection of microorganisms involved in complex microbial process, such as wine fermentations, and evaluation of their physiological state is crucial to predict whether or not those microbial species will be able to impact the final product. In the present work we used a direct live/dead staining (LDS) procedure combined with fluorescence in situ hybridization (FISH) to simultaneously assess the identity and viability of Saccharomyces cerevisiae (Sc) and Hanseniaspora guilliermondii (Hg) during fermentations performed with single and mixed cultures. The population evolution of both yeasts was determined by plating and by LDS combined with species-specific FISH-probes labeled with Fluorescein. Since the FISH method involves the permeabilization of the cell membrane prior to hybridization and that it may influence the free diffusion of PI in and out of the cells, we optimized the concentration of this dye (0.5μg of PI per 10(6) cells) for minimal diffusion (less than 2%). Fluorescent cells were enumerated by hemocytometry and flow cytometry. Results showed that the survival rate of Sc during mixed cultures was high throughout the entire process (60% of viable cells at the 9th day), while Hg began to die off at the 2nd day, exhibited 98% of dead cells at the 3rd day (45g/l of ethanol) and became completely unculturable at the 4th day. However, under single culture fermentation the survival rate and culturability of Hg decreased at a much slower pace, exhibiting at the 7th day (67g/l of ethanol) 8.7×10(4)CFU/ml and 85% of dead cells. Thus, our work demonstrated that the LDS-FISH method is able to simultaneously assess the viability and identity of these wine-related yeast species during alcoholic fermentation in a fast and reliable way. In order to validate PI-staining as a viability marker during alcoholic fermentation, we evaluated the effect of ethanol on the membrane permeability of Sc and Hg cells, as well as their capacity to recover membrane integrity after being exposed to different levels of ethanol (1%, 6%, 10%, 12% v/v). Results showed that while Sc cells were able to recover membrane integrity after ethanol exposure, Hg cells were not. However, under alcoholic fermentation Sc cells didn't recover membrane integrity after the mid-term (4-5days) of alcoholic fermentation.
Authors:
Patrícia Branco; Margarida Monteiro; Patrícia Moura; Helena Albergaria
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Publication Detail:
Type:  JOURNAL ARTICLE     Date:  2012-7-7
Journal Detail:
Title:  International journal of food microbiology     Volume:  -     ISSN:  1879-3460     ISO Abbreviation:  -     Publication Date:  2012 Jul 
Date Detail:
Created Date:  2012-7-23     Completed Date:  -     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  8412849     Medline TA:  Int J Food Microbiol     Country:  -    
Other Details:
Languages:  ENG     Pagination:  -     Citation Subset:  -    
Copyright Information:
Copyright © 2012 Elsevier B.V. All rights reserved.
Affiliation:
Unidade Bioenergia, LNEG, Estrada do Paço do Lumiar, 22, 1649-038 Lisboa, Portugal.
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