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News and Trends
The termite gut has recently received attention as a model system for lignocellulosic biomass degradation with potential industrial biofuel applications. Termites are known to efficiently digest lignocellulosic biomass (with preference for wood), and knowledge of how this works in the termite gut, can provide new and more efficient methods for the pretreatment step in cellulose ethanol production. Pretreatment involves the removal of lignin, and the degradation of cellulose, hemicellulose (and other carbohydrates) into (ethanol-) fermentable sugars from the biomass (this is almost similar to what happens in the termite gut). Lignocellulose digestion in termites are considered to be a contribution of (1) the host (termite) input (such as an expression of an enzyme which digests lignocellulose), and (2) the symbiont input, (presence of "highly specific microflora of symbiotic microorganisms" residing in the termite's hind gut which can also contribute a "cocktail" of lignocellulosic degradation enzymes). Recently, scientists from the Universities of Florida, Illinois, and the Kentucky (United States), took "a combined host and symbiont meta-transcriptonic approach for investigating the digestive contributions of host and symbiont in the lower termite, Reticulitermes flavipes". Their research showed many interesting results, and the "dual host-symbiont transcriptome sequencing effort" is reported to be the first ever to be conducted in a single termite species. The sequence data base provides a genome resource for the development of host-symbiont-derived biocatalysts for biofuel ethanol production applications. The complete study is published in the open access journal, Biotechnology for Biofuels (URL above).. http://www.thebioenergysite.com/news/4806/biofuels-future-for-aviation The bioenergysite website reports the recent meeting of Giovanni Bisignani (IATA Director General and CEO) with UN Secretary General Ban Ki-Moon, to present the aviation industry's strategy and targets with respect to the development of sustainable aviation biofuels. Among the highlights of the presentation are: (1) Among the three biggest opportunities for emission reduction in the aviation industry (technology, infrastructure and sustainable biofuels), sustainable biofuels is said to offer the most excitement, because "for the first time, air transport has the possibility of an alternative to traditional jet fuel", (2) focus is presently on camelina, jatropha and algae, because these feedstocks do not compete for land or water with food crops, and these also have the potential to reduce our carbon footprint by up to 80%, (3) four test flights using blends of sustainable biofuels have shown that they meet the technical and safety standards for use in commercial aviation; certification is expected by the year 2011, at the latest.. Biofuels Processinghttp://www.biotechnologyforbiofuels.com/content/pdf/1754-6834-2-26.pdf Pretreatment and saccharification processes are usually the first steps in the production of cellulosic ethanol from lignocellulosic biomass. The objective is to remove the tightly wrapped lignin molecules from the cellulose fibers and to convert the cellulose and other polymeric carbohydrate molecules into simple sugars. The product stream from these initial processes is called the "hydrolyzate". The hydrolyzate (which contains the simple sugars) is next inoculated with yeasts or bacteria for the ethanol production step by fermentation. When chemical methods (like acid treatment) are used in combination with heat for the pretreatment and saccharification of lignocellulosic biomass, other compounds are also released in the hydrolyzate. These compounds are said to be potentially toxic/inhibitory to the ethanol-fermenting microorganism. Thus, the proper selection of the alcohol-fermenting organism is an important consideration for cellulose-ethanol production. The bacterium, E. coli, is reported to have mechanisms which can enable it to tolerate the adverse effects of potentially toxic compounds in the hydrolyzate. Scientists from the Department of Chemical and Biological Engineering reviewed the toxicity and tolerance of E.coli to pretreated hydrolyzates, and suggested strategies to improve the microorganism for higher yields of ethanol during fermentation. The review appears in the open access journal, Biotechnology for Biofuels (URL above)..
http://www.pnas.org/content/early/2009/10/21/0905555106.abstract?sid=64206e6b-4244-40fc-8697-4c5efcff3ab2 Suberin is a polyester polymer located in the cell walls of seed and root systems of terrestrial plants. It acts as a protective barrier against pathogenic organisms or harmful substances, while facilitating the intake of water and nutrients. Suberin is also reported to have an important role in enabling plants to tolerate environmental stresses, such as dry or high saline soils. Using a model plant called Arabidopsis, scientists from the Brookhaven National Laboratory (United States) found that an enzyme called, hydroxyacid hydroxycinnamoyltransferase (HHT), is an important enzyme for suberin biosynthesis. Suberin-deficient plants were observed to be "much more permeable to salt in solution than their wild-type counterparts", indicating that "suberin plays an important role in the adaptation of plants to their terrestrial habitats". According to Brookhaven biologist Chang-Jun Liu, "identifying the key biosynthetic enzymes and understanding suberin production may be particularly important for growing plants on the marginal soils that have been proposed for use in farming bioenergy crops". Enabling biofuel crops to thrive in marginal soils can help ensure the use of productive, fertile lands for food production. Another interesting finding of the study showed that suberin polyphenolics share the same biosynthetic precursors with lignin (the tight chemical wrapping surrounding cellulose fibers in lignocellulosic biomass), but both are produced by different enzymes. This could eventually lead to the development of tailor-made bioenergy crops which are easier to digest ("pretreat") and process into biofuels, while simultaneously "redirecting photosynthetic carbon to improve carbon-sequestration efforts". The complete study is published in the Proceedings of the National Academy of Sciences (PNAS) (URL above).. Biofuels Policy and Economics
http://www.sciencemag.org/cgi/content/abstract/1180251 One of the issues related to biofuels is the magnitude of greenhouse (GHG) emissions that may arise from direct use or indirect-land use for bioenergy production. Direct land-use emissions are "generated from land committed solely to bioenergy production", while indirect land-use emissions "occur when biofuels production on cropland or pasture displaces agricultural activity to another location, causing additional land-use changes and a net increase in carbon loss". An international team of scientists from the United States, Brazil and China, examined these GHG emissions from direct and indirect effects of possible land-use change scenarios from an expanded 21st century global cellulosic bioenergy program. Using linked economic and terrestrial biogeochemistry models, the study found that (1) large greenhouse gas emissions from indirect land-use changes are "unintended consequences of a global biofuels program", and these consequences (specially if these involve clearing of forests) will actually "add to the climate-change problem rather than helping to solve it, (2) additional fertilizer that will be required to grow biofuel crops in the future will result in nitrous oxide (another type of greenhouse gas) emissions that will surpass carbon dioxide, in terms of warming potential, (3) "a global greenhouse gas emissions policy that protects forests and encourages best practices for nitrogen fertilizer use can dramatically reduce emissions associated with biofuels production". The complete study is published in an October issue of the journal, Science (URL above)..
The United Nations Food and Agriculture Organization's Bioenergy and Food Security Criteria and Indicators (BEFSCI) Project is planning to complete its "first draft of these principles, criteria and indicators", after two technical consultations scheduled in November 2009 and early 2010. The general framework of objectives will include discussions on the links between bioenergy production and food security, and a preliminary identification of criteria and indicators on sustainable bioenergy production that safeguards food security. The technical consultations will also address/discuss three specific issues: (1) key positive and negative impacts of bioenergy production on food security that should be assessed at the international, national, and project/site levels, (2) indicators that should be used to measure these food security-related impacts of bioenergy production at the international, national, and project-site levels, and (3) alternative qualitative assessment methods be used for bioenergy impacts (on food security) for which an indicator cannot beidentified or measured.. |
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