Tobacco could be biofuel of future vehicles...

Researchers have identified a way of increasing oil content in tobacco leaves as a prelude to using these for biofuel.

In some instances, the modified tobacco plants produced 20-fold more oil in their leaves, said Vyacheslav Andrianov, assistant professor of cancer biology at Jefferson Medical College.

Tobacco can generate biofuel more efficiently than other agricultural crops. However, most of the oil is typically found in the seeds - tobacco seeds are composed of about 40 percent oil per dry weight, adds Mr. Andrianov.

Although seed oil has been tested for use as fuel in diesel engines, tobacco plants yield a modest quantity of seeds, or about 600 kg per acre.

Mr. Andrianov and his colleagues sought to find ways to engineer tobacco plants to have a higher oil content.

“Tobacco is very attractive as a biofuel because the idea is to use plants that aren't used in food production,” he said. “We have found ways to genetically engineer the plants so that their leaves express more oil. In some instances, the modified plants produced 20-fold more oil in the leaves.”

“Based on these data, tobacco represents an attractive and promising 'energy plant' platform, and could also serve as a model for the utilisation of other high-biomass plants for biofuel production,” concludes Mr. Andrianov.

These findings were published online in Plant Biotechnology Journal.

(Source: http://beta.thehindu.com/sci-tech/article74003.ece)

Technical Details:

(Source : http://www3.interscience.wiley.com/cgi-bin/fulltext/123226769/HTMLSTART)

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Potential of tobacco for biofuel production

As oil prices rise and maize starch-based ethanol appears increasingly unsustainable, development of alternative feedstocks to replace food crops such as soybean and corn is crucial for wide-scale biofuel production. By overexpressing single genes, DGAT and LEC2, we demonstrated the potential of manipulating metabolic pathways for at least a twofold increase of oil accumulation in tobacco green biomass in each transformation experiment. It is tempting to assume that the over-expression of both genes in the same plant will double the accumulation of extractable FA, however it should be confirmed experimentally. Additional means of increasing oil accumulation include using other strong enhancers/promoters in combination with DGAT or other key enzymes influencing oil biosynthesis such as acetyl-CoA carboxylase (Klaus et al., 2004), thioesterase (Dörmann et al., 2000), gene amplification technology (Borisjuk et al., 2000), blockage of lipid breakdown (Scolombe et al., 2009), or inhibition of the pathways that divert energy and metabolite flow from oil biosynthesis. Special consideration is required for the enzymes leading to the synthesis of PA, that could be a bottleneck for further increases in TAG and phospholipid accumulation, as indicated in this study (Figure 3, Table 1).

There is also a number of options for choosing an optimal tobacco host species that possesses higher natural oil content (Koiwai et al., 1983), high-sugar content and bred (McCabeet al., 2008) or genetically engineered tobacco with improved biomass charactecteristics (Sticklen, 2006). While overexpressing oil biosynthesis enzymes generally had a limited effect on oil accumulation in seeds (Wu and Chappell, 2008), the limit of enhanced oil accumulation in the green parts of plants is not yet known. As an example, high-level terpene production was engineered in tobacco by diverting carbon flows that result in more than 1000-fold increase in specific terpene biosynthesis (Wu et al., 2006).

Assuming a conservative 170 metric tons/ha tobacco harvest, which translates into approximately 20 tons of dry biomass, engineered tobacco plants with an achieved level of 6% FA per dry weight will produce at least twice as much bio-diesel as a hectare of soybean (Durrett et al., 2008). However, it should be recognized that extraction of biofuel grade FA from green biomass represents a bigger processing challenge compared with the well-established method of pressing oil from plant seeds. Following oil extraction, which will also produce glycerine, the remaining biomass could be further utilized for ethanol production by fermentation (Hahn-Hägerdal et al., 2006). The concept and advantages of tobacco biomass for ethanol production have been proven by a Virginia start-up company, Floyd Agricultural Energy Cooperative Ltd., in the early 1980's during the surge of oil prices caused by an Organization of Petroleum-Exporting Countries embargo. As a result of recent progress made with respect to decreasing the cost of enzymes, optimizing the method of pretreatment, and developing more efficient yeast strains, fermenting tobacco biomass into ethanol has become even more feasible (Olofsson et al., 2008). By generating both biofuel oil and ethanol, tobacco has the potential to produce more energy per hectare than any other non-food crop.