News article: http://www.basqueresearch.com/berria_irakurri.asp?Berri_Kod=4745&hizk=I#.Ul0MltKVOCY

In Spain, a researcher has genetically modified a tobacco plant so that it could store high levels of starch in the leaves and produce high amount of fermentable sugars for biofuel production.

In her PhD dissertation research, Ruth Sanz-Barrio used a specific protein known as thioredoxin f  to regulate the metabolism of carbohydrates and to obtain a significant increase in the amount of starch in the tobacco leaves, which could reach 700 percent with respect to the amount obtained from non-modified control plants. The leaves of the genetically modified tobacco plants could release 500 percent more fermentable sugars, which could be turned into bioethanol.

Based on a theoretical calculation, one could obtain up to 40 liters of bioethanol per ton of fresh leaves, or almost ten-fold increase in bioethanol yield with respect to the control tobacco plant. The non-edible tobacco could potentially replace food crops as alternative source of biofuels.The estimated starch yield potential of the modified tobacco could match those of cereal crops like barley or wheat. 

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News release: http://newsroom.ucla.edu/portal/ucla/ucla-engineers-develop-new-sugar-248452.aspx

Journal reference (abstract): http://www.nature.com/nature/journal/vaop/ncurrent/full/nature12575.html

Scientists at the University of California at Los Angeles (UCLA) have created a new synthetic metabolic pathway for breaking down glucose, which conserves carbon and promises to increase biofuel production by 50 percent.

The new pathway is a modification of the natural metabolic pathway known as glycolysis, a series of chemical reactions that lead to the conversion of glucose sugar into important molecular precursors. Glycolysis converts four of the six carbon atoms found in glucose into two-carbon molecules known acetyl-CoA, a precursor to biofuels like ethanol and butanol, as well as fatty acids, amino acids and pharmaceuticals. However, the two remaining glucose carbons are lost as carbon dioxide.

The net loss of two carbon atoms is a major gap in the efficiency of glycolysis, which is currently used in biorefinies to convert sugars derived from plant biomass into biofuels. To address this, the UCLA research team rerouted the glycolytic pathway so that all six glucose carbon atoms can be converted into three molecules of acetyl-CoA without losing any as carbon dioxide.

The new pathway uses enzymes found in several distinct pathways in nature. The team genetically engineered E. coli bacteria to use the synthetic pathway and demonstrated carbon conservation and production of even more product. The researchers dubbed this new pathway non-oxidative glycolysis, or NOG.

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News release: http://news.cornell.edu/stories/2013/10/researchers-survey-how-green-grows-your-switchgrass

Cornell University researchers are looking at the long-term sustainability impacts of growing switchgrass on marginal lands.

Switchgrass has been identified as a potential second generation biofuel crop. This perennial grass grows well on marginal soils that are unsuitable for most conventional agricultural crops. In many cases those marginal soils are wetter and more prone to a process called denitrification, in which nitrate from fertilizer is converted back to gaseous forms. A small percentage ends up as nitrous oxide, which is considered a primary threat to the atmosphere's ozone layer.

The United States is mandated by law to increase the volume of renewable fuel to be blended into transportation fuel to 36 billion gallons by 2022, of which 21 billion gallons will be ethanol derived from non-edible sources. As the area devoted to biofuel crop production continues to expand, bioenergy researchers need to look at the impact of marginal soil-grown biofuel crops on nitrous oxide emissions.

Cornell scientists have been measuring emissions of nitrous oxide and other trace gases emanating from the soil planted to switchgrass throughout the growing season. They are also measuring crop yields and tracking beneficial changes in soil carbon storage and overall soil health. The first results from this study are expected by late 2013.

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News release: http://www.uq.edu.au/news/?article=26778

In Australia, a research group at the University of Queensland is genetically modifying baker's yeast to produce the chemical found in lemons and other citrus fruits, which can be used as a jet fuel component.

The Systems and Synthetic Biology Group at the Australian Institute for Bioengineering and Nanotechnology is modifying baker's yeast to produce a synthetic form of limonene, a volatile chemical that gives citrus fruits their characteristic smell. Limonene was first identified in turpentine oil in the late 1800s and is now used as a flavor and fragrance in foods, household cleaning products and perfumes.

Previous demonstrations have shown the usefulness of limonene extracted from citrus peel as a jet fuel component. The process of extracting it on a large scale is highly impractical and not commercially viable. The Australian group is pioneering the use of yeast cells as limonene biofactories by transferring into them the genes responsible for limonene production.

Efforts to obtain jet fuel from limonene is the latest in a series which has seen cutting-edge science used to transform the often ancient practices of agriculture to multi-faceted and profitable methods for tomorrow. These kinds of projects will allow farming and resources to move into a new age, as non-renewable energy sources diminish.

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News release: http://news.illinois.edu/news/13/1008biofuels_Yong-SuJin.html

Journal reference (abstract): http://www.nature.com/ncomms/2013/131008/ncomms3580/full/ncomms3580.html

Researchers from the University of Illinois at Urbana-Champaign and University of California at Berkeley have used metabolic engineering to develop a yeast strain that is capable of using both xylose sugars and acetic acid for the production of ethanol.

The study aimed to address the limitations of microbial conversion of lignocellulosic biomass or raw materials from wood, grasses and inedible plant parts into ethanol via fermentation process. Most of the lignocellulosic biomass is made up of xylose sugar which is difficult for the baker's yeast (Saccharomyces cerevisiae) to ferment. Also, other biomass components lead to the formation of acetic acid during metabolism, which is toxic to fermenting microorganisms and so further reduces ethanol yields.

The pathway for xylose metabolism was realized by adding the genes xylose reductase and xylitol dehydrogenase from S. stipitis to the metabolic repertoire of S. cerevisiae. The pathway produces excess NADH, an electron-transfer molecule that is part of the energy currency of all cells. The yeast was later induced to consume toxic levels of acetic acid by expressing bacterial enzymes that catalyze this process. The enzymes not only converted acetic acid into ethanol, but also would use the surplus NADH from xylose metabolism.

The innovative strategy, reported in the journal Nature Communications, increases ethanol yield from lignocellulosic sources by about 10 percent. The results demonstrate how an undesirable redox state can be exploited by metabolic engineering to drive desirable reactions—even improving productivity and yield.