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GM yeasts: the next battleground  

Iím going to make a prediction. I reckon the next battleground in the wine world will be the controversial use of genetically modified (GM) yeasts in winemaking. Plenty of these genetically modified strains already exist in laboratories around the globe, but they havenít previously been commercialized because of the negative reactions of consumers to GM food products. The scientists are busy engineering beneficial traits into wine yeasts even though they know they wonít be useful for commercial winemaking for the forseeable future, for two reasons. First, they reckon the public oppisition to GM technology will one day recede, at which point theyíll be in a good position to move. Second, they can learn a lot of useful information from using these introduced genes, which will then inform conventional breeding and selection programs.

Now, however, a GM yeast strain, called ML01, has been commercialized and is authorized for use in the USA. This yeast, made by Springer Oenologie, has been the recipient of two extra genes (known as transgenes). The first is a malate transporter gene from another yeast, Schizosaccharomyces pombe, and the second is the malolactic enzyme gene from Oenococcus oeni, the main bacteria responsible for the natural malolactic fermentation that occurs in many wines after alcoholic fermentation. This yeast is therefore able to carry out malolactic fermentation (normally done by bacteria) at the same time as alcoholic fermentation.

There are several advantages to this. The first is that processing wine becomes much faster. The second is that there is less risk of wine spoilage because there is no delay between alcoholic fermentation and the onset of malolactic fermentation, a stage at which wine can be at risk. Also, the resulting wine is less likely to contain biogenic amines which are produced by the bacterial malolactic fermentation and which can have negative health effects.

In the USA yeasts are classified as processing agents, and thus wines made with this yeast would need no declaration that they contained GM ingredients. This allows GM yeast to enter winemaking Ďunder the radarí, with consumers or advocacy groups none the wiser. In many other countries, such as New Zealand and Australia, the regulations are more stringent, and yeast is considered as part of the ingredients of wine.

So is anyone making wine using this GM yeast? If they are, they arenít telling anyone, for understandable reasons. In response to the commercial approval of ML01 in the USA, the Australian Wine Research Institute has issued a statement declaring that no GM yeasts will be used in Australian wine for the foreseeable future. But because it is so much easier to produce yeasts with desirable properties by GM technology (and there are some traits that are impossible to select for by conventional breeding), research continues apace globally on GM yeast technology.

So whatís the big deal? Arenít GM microbes used all the time? The insulin diabetics inject is produced by GM bacteria, for example, and given proper testing, thereís no reason to worry about safety issues. Supporters of the technology argue that what they are doing by developing GM yeast strains is not with the intention of creating fake wines, but with a view to unlocking the latent flavour and aroma potential of grape must by using yeasts with special properties. One yeast researcher has even gone on record as stating that the best wines are still to be made, and that this technology is one way forward.

What do I think? As a scientist who cares a great deal about the future of wine, I favour a cautious approach: if GM yeasts become widespread, the danger is that wine will be seen as just another manufactured beverage. If we kill the Ďnaturalnessí of wine, we run the risk of destroying the whole venture. So although it rankles with me a bit to knock the elegant science involved in engineering new wine yeasts, Iím afraid Iím going to voice my disapproval at the use of GM yeasts in wine. I think itís time we drew a line in the sand and banned the use of GM organisms in winemaking.  

see also www.wine-science.com

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