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[SANET-MG] high ethanol bakers yeast
Thank you for the interesting questions. I read the paper in science
along with its accompanying on-line 32 page description of the genetic
methodology used to create the high ethanol yeast.Before answering your
questions I will go into the methodology a bit. I will mention that I
taught Microbial Genetics for over twenty five years and published in
both yeast and fungal genetics and molecular biology.
The system developed for making high ethanol yeast is certainly genetic
engineering but it is not genetic modification with transgenes. Key
regulators for production of high level ethanol in the presence of high
level glucose were identified in yeast. Those genes DNA sequences were
altered by a process called site specific mutagenisis then reinserted
into the yeast at a particular locus (the uracil gene). The regulatory
genes controlled a number of genes in a metabolic network for ethanol
production and most importantly ability to tolerate high levels of
ethanol and glucose.
The current work on such key regulators follows work on E coli ethanol
production by modifying a sigma factor regulator of transcription.
Douglas asked "However, we could call the effect I refer to "genome
shifting",which adds an unknown, unforeseeable and uncontrollable
element to the expected results. Do you agree?" I do not entirely agree.
Yeast genetics are far more precise than the crude methods used in crop
plants and the genes in the yeast have been precisely altered by
mutations on knowingly altered DNA. Manipulating a metabolic network is
new and breathe taking but could lead to unexpected toxins being
produced.These will have to be checked on in the near future but since
the yeast is not for very strong beer but for commercial ethanol fuel
the toxins could be ignored. A former student and colleague, Inge
Russel, developed a very high ethanol yeast by breeding and selection
alone and her strain is presently better than the promoted higher tech
system because it was bred from a commercial ethanol yeast rather than
into the laboratory strains used in the high tech version.Lab yeast tend
not to do all that well in commercial operations for brewing, wine
making or ethanol making.
The gene regulators are somewhat similar to the MADS box regulators
growing popular in crop genetic manipulation that I discussed
previously. However, the MADS box alterations have been transgenic while
the network ethanol yeast are not.
Douglas asks "To what extent is the GE yeast likely to cross with native
yeasts existing in nature? Is the threat similar to that created by GE
crops, or are GE yeasts likely to be less threatening? You ask an
important question Douglas. My feeling this that regulators will have a
hard time getting their teeth into genes that are precise;y altered
within a particular organism. If unexpected toxins are produced because
of metabolic network alterations then we are in real trouble. Bakers
yeast is not a pathogen to anything , I believe, but it has been used as
a probiotic. Killer beer is every boy's nightmare! However, the toxins
should show up early and be dealt with promptly or even ignored for
making fuel.However, toxic ethanol yeast in the gut would not be any fun
Manipulating metabolic networks is brand new but clearly here to stay.
Organic farmers and the industry will soon be faced with difficult
decisions about organic foods. Can genes and networks manipulated by
engineered DNA code word changes within a crop be considered organic?
We will soon have to decide.Let us hope the decision is ours and not
Finally, many recollect that I objected to GM wine and I still do. That
stuff is transgenic and should be labeled, dammit all. You cannot
imagine the abuse I get from the developers of GM wine!
Thanks so much for the important questions, excuse my rambling answers.
In relation to your important "Making the World GM-Free &
Sustainable" post, I would appreciate knowing your perspective
regarding the events described here:
My thoughts: There are aspects to this issue that are not mentioned
in the article because neither Reuters nor the people at MIT
involved in the creation of the GE yeast that's discussed in the
article appear to be aware of certain characteristics common to all
GE organisms due to the effects of the processes used to insert the
foreign (or in this case, extra) gene.
They apparently assume that the GE yeast referred to in the article
is simply the original yeast with an added gene.
However, we could call the effect I refer to "genome shifting",
which adds an unknown, unforeseeable and uncontrollable element to
the expected results. Do you agree?
Another issue I'd like your opinion on is: To what extent is the GE
yeast likely to cross with native yeasts existing in nature? Is the
threat similar to that created by GE crops, or are GE yeasts likely
to be less threatening?
Thanks in advance for your thoughts and any orientation you can
Baker's Yeast Mutant Can Boost Ethanol Output - MIT
NEW YORK - Scientists have engineered baker's yeast to produce
ethanol faster and more efficiently, according to a Massachusetts
Institute of Technology research paper published on Thursday.
The US government is urging greater use of ethanol as a way to
stretch domestic motor fuel supplies and make the country less
dependent on foreign oil. US demand for ethanol has also jumped as
the oil industry uses it to replace gasoline additive MTBE, a
suspected carcinogen banned in several states.
The MIT scientists made "super" baker's yeast, by adding a gene
already found in the microbe, to speed up ethanol production by
about 50 percent. That could allow ethanol plants either to make
more of the fuel in less time, or make more of the fuel in the
same time, said Dr. Hal Alper, one of authors of the paper,
published on Thursday in the international weekly science journal,
The MIT scientists engineered the baker's yeast to survive high
levels of ethanol and sugars found in the processing of the fuel
that kill other fermenting microbes. "The end result is that you
have yeast cells that are able to survive and grow in the presence
of a toxic chemical," said Alper.
The yeast can survive high levels of glucose and there's no reason
why it won't survive in high levels of xylose, the other main sugar
found in cellulosic ethanol, he said.
The research was funded by the DuPont-MIT alliance, a collaboration
between the DuPont Co. and the university, the National Institutes
of Health, and the US Department of Energy, and others
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