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A fine vintage for biotech.

Winemaking is seen by many winemakers as an art rather than a science. While I believe that blending different wines to produce a truly "great wine" is indeed an art, growing grapes and fermenting grape must is undoubtedly a scientific process.

Over the past 15 years I have employed cutting-edge technologies to improve wine yeasts that will prevent the formation of allergens and ethyl carbamate (EC), a carcinogen found in wines. These novel yeast strains were the first two functionally improved wine yeasts to receive Generally Regarded As Safe (GRAS) status from the U.S. Food and Drug Administration, and Health Canada and Environment Canada.

Grape must is fermented to ethanol and flavour compounds by the yeast Saccharomyces cerevisiae. Chardonnay wines and red wines usually undergo a secondary fermentation called "malolactic fermentation." Winemakers inoculate wines with the bacterium Oenococcus oeni, however, wineries often have sluggish or stuck malolactic fermentations that lead to the production of more than 20 bioamines. These can cause migraines, hypotension, diarrhea, and so on in sensitive consumers; around 33 per cent of the world's population is sensitive to bioamines in wine.

The malolactic wine yeast, ML01, constructed in my laboratory, conducts the alcoholic fermentation and degrades malic acid to lactic acid during the alcoholic fermentation. This yeast prevents the formation of bioamines in wines. S. cerevisiae ML01 is the first genetically enhanced wine yeast to be commercialized by the wine industry in the U.S. and Canada.

In 1985 the Liquor Control Board of Ontario discovered that many wines contained excessive amounts of EC, which is considered potentially dangerous to humans since it exhibits carcinogenic activity in a variety of laboratory animals. Extensive studies revealed that EC increases the rates of cancer of the liver, lung, harderian gland, and of hemangiosarcomas in both female and male mice. EC also increased the rates of cancer of the mammary gland and ovaries in female mice and the rates of skin cancer and cancer of the forestomach in male mice. EC is now classified as a Group 2A probable carcinogen in humans; the LCBO set a legal limit of 30 [micro]g/L for EC in wine sold in Canada.

During 2005 I bought 55 wines ranging in price from $9 to $55 per bottle off the shelf in a liquor store in British Columbia. After accelerated aging simulation of these wines the EC levels ranged from nine to 215 [micro]g/L. Only nine out of 55 wines had EC concentrations below 30 [micro]g/L.

This is another problem that can be addressed using genetically enhanced yeasts. The metabolism of arginine--one of the major amino acids found in grape must--by wine yeast leads to production of ornithine and urea. Ethanol and urea released by yeast cells during alcoholic fermentation are the major precursors for EC in wine.

S. cerevisiae degrades urea in a two-step reaction yielding ammonia; the DUR1,2 gene encodes the enzyme urea amidolyase which catalyzes this reaction. We have now expressed the DUR1,2 gene under control of a constitutive yeast promoter in ten different wine yeast strains. The functionally improved yeast strains minimize the production of EC in wine by up to 92 per cent. These yeast strains are genetically stable and substantially equivalent to the original industrial wine yeast strains.

The low EC producing yeast strains were tested independently by the wine industry in the U.S. and Chile and laboratory data were confirmed. Functional Technologies Corp. in Vancouver has licensed the technology from The University of British Columbia and a yeast plant is currently being built in P.E.I. The yeast strains will be available for commercial winemaking around the world during 2010.

In this age of biotech, science has the ability to smooth out the rough edges of the ancient art of winemaking and wineries can now produce wines that are fully safe for the consumer.

Hennie JJ van Vuuren is a pioneer in the field of metabolic enhancement of wine yeasts. He is founding director and professor at The University of British Columbia's Wine Research Centre.
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Author:van Vuuren, Hennie J.J.
Publication:Canadian Chemical News
Date:May 1, 2010
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