ISIS Report 05/01/07
GM Wine Sold Unlabelled in the United States
Prof. Joe Cummins
exposes the potential hazards of the GM wine yeast that has been approved as
safe by the US Food and Drug Administration and advises against drinking US
wines
A fully referenced version
of this article is posted on ISIS members’ website. Details
here
GM wine by stealth
Did you know that genetically modified (GM) wine has
been marketed in the United States for the past three years?
In 2003, the
United States Food and Drug Administration (FDA) designated the GM yeast strain
Saccharomyces cerevisae ML01
‘generally recognized as safe’ (GRAS). The strain included a gene for malolactic
enzyme from the bacterium Oenococcus oeni
and a malate permease gene from the fission yeast Schizosaccharomyces pombe. Wine making involves
alcoholic fermentation via the metabolic pathways of yeast and the malolactic
pathway to convert malic acid to lactic acid, to reduce the acidity of the
wine. Malolactic acid fermentation is usually achieved using lactic acid bacteria,
which have a permease for malic acid. Putting the two fermentation pathways
in one organism seems a good idea.
The yeast ML01 was modified
using a shuttle vector containing a chromosome integration cassette with genes
for malolactic enzyme, malate transporter (permease), regulatory genes and a sequence directing
homologous recombination at a chromosomal locus (not specified in the FDA
report), and the antibiotic phleomycin gene was used as a selectable marker
via another plasmid. After culturing the selected antibiotic resistant lactic-acid
producing yeast, a phleomycin-sensitive lactic acid producing strain was isolated
and found to contain the integrated malolactic-malate transporter genes. The
original anti-phleomycin plasmid did not contain a sequence allowing it to
be integrated into the yeast chromosome and the plasmid was therefore unstable
and frequently lost from the yeast cell [1]. The company distributing the
GM yeast, Springer Oenologie, Lesaffre Group of North America, stated that the malate transporter gene
and malolactic gene were both controlled by the phosphoglycerate kinase gene
(PGK1) promoter and transcription terminator. The recombinant
yeast softened the wine’s ‘mouth feel’ by decreasing its acidity, and also
reduces buttery flavours (diactyl) due to lactic acid secondary metabolism
[2].
Genetic modification of yeast and bacteria differs fundamentally from modification
of plants. The modification of bacteria and yeast is based on homologous recombination
while modification of plants is based on illegitimate recombination. In plants
the recombinant gene insertions are not precise and disrupt genes that are not
specifically targeted, while in yeast, gene insertions disrupt genes that are
targeted. For yeast genetic engineering ‘shuttle’ vectors are used, which are
propagated in bacteria for insertion in yeast. The shuttle vector may also replicate
autonomously in the yeast nucleus and express genes equipped with promoter and
terminator genes. The expression vector comes equipped with a sequence homologous
with a yeast chromosomal gene. Recombination between vector and chromosomal
gene disrupts the target chromosomal gene and inserts the transgene, and frequently
also a selectable marker, into the yeast target locus [3].
The yeast released
for commercial wine production, ML01, was found to be only somewhat substantially
equivalent to unmodified wine yeast, as a cytochrome p450 enzyme protein appeared
to have been altered from the parental strain based on a comprehensive analysis
of the yeast cell proteins, and a number of codon changes were
observed in the inserted malolactic gene cassette, but those changes were
not considered significant. Strain ML01 was claimed to reduce levels of amines
such as putrescine and cadaverine, preventing unpleasant side effects of wine
drinking [4].
Wine yeasts genetically unstable and DNA persists in wine
Neither the FDA document [1] nor the publications
on ML01 [4] considered important complications associated with
wine yeast. Wine yeasts are unstable and sudden losses in heterozygosity have
been observed. Such abrupt changes in the phenotype of wine yeasts are commonplace
[5]. Numerous translocations have been observed uniquely in wine yeasts
and such chromosome rearrangements involving transgenes can lead to unexpected
toxicity in the final product [8]. Yeast cells in wine were found to be hyperactive
in mitotic recombination, contributing to the observed instability of wine
yeasts [7].
How much yeast nucleic acid (DNA and RNA)
is carried over into wine? Autolysis of wine yeast releases nucleic acids
that persist in the wine for at least nine years and contribute to the flavour
of wine [8]. The fate of yeast and plant DNA, as monitored by yeast chitinase
gene and the plant chlorophyll a/b binding protein gene and micro-satellite
markers showed that large DNA markers were present in must (the starting fermentation
mixture of mainly yeast and grape juice), while the 250 base pair
micro-satellites were present in both must and young wine for up to six months
[9].
Culturable yeast cells were isolated from
two out of five bottled wines that had been filtered prior to bottling, and
originating from different locations in Greece. Unfiltered wines stored on oak barrels between
1998 and 2002 all contained live yeast [10]. The FDA letter designating wine
yeast ML01 to be GRAS indicated that the distributor of GM yeast believed that final wines were free
of yeast and yeast DNA, but no data were provided to support that conclusion.
The dissemination and survival of commercial
wine yeast in the vineyard was studied over a period of three year, which
indicated that the strains were mainly recovered at fairly close proximity
to the winery, up to 200 metres. The yeast was largely disseminated by water
runoff. The commercial strains tended to appear and disappear from the vicinity
of the winery [11].
The yeasts from a winery abandoned in 1914
differed from those isolated in a modern winery; with the genetic characteristics
of the yeast in the abandoned winery persisting for over ninety years [12].
A study of wine jars from the tombs of ancient Egypt showed that S. cerevisiae had been used in winemaking
by at least 3150 BC [13]. Regulators should take note of the time that GM
yeast may persist.
FDA reviews reads like pr on behalf of GM wine
In the United States, approval of GM plants such as grapes
is granted by USDA/APHIS and those reviews
provide fairly full information that is made accessible to the public. FDA
alone reviews and approves GM microbes such as yeast used in food products.
Their full reviews including all required support information does not appear
to be readily accessible, and their approval reports, such as the GRAS notice
on GM wine yeast reads more like
a public relations release on behalf of the promoters of GM wine yeast [1].
The FDA review did not consider the environmental and human health consequences
of marketing and consumption of GM wine. The
view that the yeast and its
autolysis products including DNA, RNA, proteins and carbohydrates are somehow
lost from the wine is not supported
by scientific evidence. The GM wine yeast does not appear to have been tested
for toxicity in animal feeding experiments, nor was the must and finished
wine.
A medical journal, The Lancet, pointed out that international
faith in the FDA is fast eroding because approvals are frequently influenced
by political pressure [14], and the approval of wine yeast certainly left
fundamental questions unanswered. It is surely premature to market GM wine
yeast, and as the wines produced using GM yeast are not labelled, it is only
prudent for consumers to avoid US wines unless there is information available
indicating that GM wine yeasts have not been used.
Van Vuuren, one of the patent holders on GM
yeast, was recently quoted as saying that [15],“several wineries were using
the ML01 yeast as of a few years ago”, but “it is not known if they or others
are using it today or exporting wines containing it.” Furthermore, “The company
marketing these GE yeast has no legal obligation to identify their customers
and has not done so.” Van Vuuren also said “he had heard that some European
wineries were buying the yeast in California and shipping it to Europe.”
The Pew Report on GM Wine and Grapes asks
[15]: “Are some US
and European wineries using this GM yeast for commercial production, or merely
for research purposes? If the yeast is being used in producing commercial
wines, and these wines are being exported to countries in which it has not
yet been approved for use, what can or should the wine industry do about it?”
Currently there are no validated
methods to detect GM wine made using GM yeast ML01, and it would be necessary
to have develop one.
The Industrial College of the Armed Forces (USA) indicated that
the “biotechnology industry is a critical element of national power” [16].
I hope that military force won’t be used to make people drink the GM wine.
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