Mannoproteins: Analysis, identification and improved release
Bauer, F F
University of Stellenbosch. Faculty of AgriSciences. Institute for Wine Biotechnology
Wine yeast contribute significantly to the aroma, the flavour, the mouth feel and the visual appearance of wine. Several of these wine attributes have been shown to be positively affected by the presence of a group of compounds collectively referred to as mannoproteins. In particular, several studies have shown that the release of such proteins by yeast during fermentation has a significant influence on the organoleptic quality of wine, in particular the mouth feel, and can protect wines against haze formation and pinking, defects that may in particular affect white wines and lead to significant economic losses. However, most yeast strains appear to be unable to release significant levels of such proteins.
Along with polysaccharides, mannoproteins form an important part of the yeast cell wall and directly affect cell wall related behaviour or phenotypes. Mannoproteins have been shown to influence the hydrophobicity of the cell wall and to directly control cell to cell adhesion phenotypes such as flocculation (floc forming cell populations with increased sedimentation efficiency) and cell to substrate adhesion. Mannoproteins are typically released by wine yeast into fermenting must during alcoholic fermentation, as well as into wine upon contact with yeast lees. Thus, cell wall mannoproteins could positively affect wine clarification and filterability.
While some information regarding the nature of haze protecting mannoproteins has become available in recent years, very little is known about the underlying molecular processes and about how cell wall composition and cell wall regulatory processes influence the release of such proteins. Understanding such processes is a prerequisite for the future selection of new yeast strains that would secrete optimised levels of specific haze protection proteins.
In the first project, a number of indispensable tools for mannoprotein analysis and the analysis of their impact, in particular the prevention of haze formation in wine, will be established. This project will run for two years. A second project will make use of the large number of yeast strains generated at the IWBT in previous projects that carry deletions or overexpression constructs of genes that directly affect mannoprotein production (cell-wall related transcription factors) or themselves encode cell wall mannoproteins. Once the roles and impact of these proteins with regard to the release of wine related mannoproteins has been established, the information will be used for the development of new mannoprotein releasing yeast strains. The projects will also involve collaboration with Ramon Gonzales from the Centre for Industrial Fermentation in Madrid, Spain.
Ndlovu, T, Divol, B Moore, J P and Bauer, F F. 2010. Yeast protein release and haze formation during aging in model wine. Poster presented at the Cape Biotechnology Forum. Somerset West, South Africa
Duckitt, E, Du Plessis, G, Strydom, M, Ndlovu, T, Govender, P, Bauer, F F, Divol, B and Moore, J P. 2010. Functional analysis of FLO gene expression in yeast (Saccharomyces cerevisiae) and developing a rapid screen for mannoprotein modified wine yeast strains. Paper presented at the 4th International Congress of the South African Society for Enology and Viticulture. 28-30 July, Cape Town, South Africa.
Moore, J P, Nguema-Ona, E E and Vivier, M A. 2010. Cell wall omics: Tracking the careers of grape and wine polymers using biotechnology and systems biology. Paper presented at the Cape Biotechnology Forum. 24-26 March, Somerset West, South Africa
Ndlovu, T, Divol, B T, Moore, J P and Bauer, F F. 2010. Bio-transformations and bioprocess: Yeast protein release and haze formation during aging in model wine. Paper presented at the Cape Biotechnology Forum. 24-26 March, Somerset West, South Africa
Moore, J P, Nguema-Ona, E E, Ndlovu, T, Divol, B, Nieuwoudt, H H, Bauer, F F and Vivier, M A. 2010. Methods to track grape and yeast derived cell wall polymers in wine – applications for wine biotechnology. Paper presented at the 12th International Cell Wall Meeting. 25-30 July, Porto, Portugal
Ndlovu, T, Divol, B, Moore, J P and Bauer, F F. 2011. Selected yeast strain can reduce protein haze formation in wine. Paper presented at the 18th Conference of the South African Society for Microbiology. 24-27 November, Warmbaths, South Africa.
Ndlovu, T, Divol, B, and Bauer, F F. 2011. Influence of yeast strain on wine haze: Exoproteomic differences between Saccharomyces cerevisiae and Saccharomyces paradoxus yeast strains. Presentation at the 2nd Wine Sciences Research Day. University of Stellenbosch, Department of Viticulture and Enology, Stellenbosch, South Africa
Ndlovu, T, Divol, B, and Bauer, F F. 2011. Hazy wine – using yeast to make it crystal clear. Presentation at the New Voices in Science. University of Stellenbosch, Stellenbosch, South Africa.
Bauer, F F, Bester, M C, Govender, P. 2010. Yeast flocculation and its biotechnological relevance, Applied Microbiology and Biotechnology, v. 88 (1) (p. 31-39)
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Govender, P, Kroppenstedt, S, Bauer, F F. 2011. Novel wine mediated FLO11 flocculation phenotype of commercial Saccharomyces cerevisiae wine yeast strains with modified FLO gene expression, FEMS Microbiology Letters, v. 317 (p. 117-126)
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