Apr
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Engineering Switchgrass For More Ethanol
April 1, 2011 | 1 Comment
The team’s paper, “Genetic manipulation of lignin reduces recalcitrance and improves ethanol production from switchgrass” has been published in the Proceedings of the National Academy of Sciences and is available in a pdf download. It’s only a 6-page read. There the researchers describe their transgenic version of switchgrass as one that produces about one-third more ethanol by fermentation than conventional switchgrass. This improved plant feedstock will be able to generate more biofuel per acre, benefiting not only the transportation sector but also the growers and farming community.
Switchgrass Enhanced for Less Recalcitrance. Click image for more info.
Research has developed biomass conversion processes for production of ethanol and other biofuels, but they remain costly primarily because of the intrinsic “recalcitrance” of biomass.
Jonathan Mielenz, a co-author and member of the Department of Energy lab’s BioEnergy Science Center explains, “Recalcitrance, or a plant’s natural defenses against insects, fungus and the weather, is widely acknowledged as being the single biggest barrier to the production of biofuel and biochemicals from switchgrass and other lignocellulosic materials.”
Jonathan Mielenz In His Lab with a Switchgrass Sample. Click image for the largest view.
Researchers have years invested seeking better ways to break down the plant’s structural defense system. While substantial progress has been reported, recalcitrance remains the main challenge of getting sugars out of plants for fuel production.
Switchgrass holds great promise as a bioenergy feedstock because it is an America native perennial plant, grows with high yields, requires little nitrogen and water and has a very wide growing range including marginal lands where food production isn’t competing. These characteristics make it an attractive target for transgenic improvements.
The path used by the genetic team led by Zeng Yu Wang of The Samuel Roberts Noble Foundation in Ardmore, Okla., was choosing to “downregulate” – a process that involves decreasing a cellular component – the caffeic acid 3-O-methyltransferase, or COMT gene in the Alamo variety of switchgrass. The change decreased the plant’s structural “glue,” known as lignin, by about one-eighth. The scientists chose this gene based on encouraging results of lignin modification from previous Noble research conducted in alfalfa and other plant species.
The result the Noble Foundation ended up with, as discovered by the fermenting team led by Mielenz, is a switchgrass that is more easily converted to biofuels under milder conditions and with much lower costly additions during fermentation.
Wang picks up the narrative, “The presence of lignin in plant cell walls interferes with the fermentation to produce biofuels,” who noted that enzymes are the single largest processing cost component for bioconversion of biomass after the biomass itself. “The transgenic lines require lower temperature preprocessing and only one-quarter to one-third the level of enzymes for equivalent ethanol fermentation compared to the unmodified switchgrass. This significantly lowers the cost of biofuels and biochemicals from this switchgrass.”
At first look from the press release the improved ethanol production looks great, but a little digging offers other important news. The transgenic switchgrass requires lower chemical and energy inputs in the form of lower pretreatment severity compared with wild type. That applies to pretreatment where more sugars are kept available for fermentation. Most noteworthy is the new lines need only ¼ to 1/3rd the level of enzymes as Wang noted, the second lost expensive cost for fuel production after the raw material, which could cut production costs close to 25% along with the production increase.
The paper winds up with another important point, “The reduced recalcitrance of these improved switchgrass lines will impact more than biomass ethanol production. Newly emerging bio-based fuels such as butanol, isobutanol, and fermentation “green gasoline” will require a biomass-based feedstock for improved economics and long-term sustainability. Because switchgrass is a perennial crop that easily survives for more than 10 years and allows the harvest of large annual production of biomass, utilization of the transgenic approach probably is one of the most effective and economical ways for feedstock improvement. Together with the development of new processing and conversion methods, this technology will enable the development of an economic and efficient industry converting lignocellulosic biomass into liquid fuels.”
This is major progress mostly overlooked for over a month, your humble writer included. It’s also just a first step. Someone will take switchgrass further. Biomass to fuel using biology is still in the hunt for the future’s fuel market.
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I love these articles, but…how long until commercialization?
Also, if we reduce a plant’s natural resistance to disease, and monocrop…..