Abstract
In the vineyard, many genera of yeast can be present on the grapes, but they are eventually outcompeted by Saccharomyces yeast as fermentation progresses. A selective pressure that has the potential to affect the composition of the non-Saccharomyces community is UV light, particularly in places with very high levels of UV-B (280–315nm) radiation like New Zealand. Understanding this ecology could conceivably be very important because of growing evidence that non-Saccharomyces yeast present on grapes in vineyards can play a role in the fermentation process and terroir. Thus, understanding how UV light can affect community composition of these yeast represents a step towards understanding how specific taste signatures derived from certain microbial communities are produced. To gain a full understanding of these processes, overall UV sensitivity to wavelengths encountered in the vineyard would need to be characterized for each member of the non-Saccharomyces vineyard yeast community. Problematically, traditional UV sensitivity assays have made use of instruments that only emit at 254nm (UV-C), a wavelength that is filtered out by the ozone layer in natural environments. Here we present a method that allows for experimental determination of UV-B sensitivity in yeast (and presumably sensitivity to several other wavelengths) that utilizes a Rayonet RPR-100 photochemical reactor. This method outperforms traditional methods of irradiation with respect to ecological relevance and with respect to tight control of wavelength and flux. With our protocol, a better understanding of the ecological processes that drive community structure in vineyards and therefore also microbial terroir can be achieved.
- photochemical reactor
- Saccharomyces cerevisiae
- sunlight exposure
- ultraviolet light
- vineyard yeast
- yeast ecology
- ©2017 by the American Society for Enology and Viticulture
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