Switchgrass cultivated during a year of severe drought inhibited microbial fermentation and resulting biofuel production.
The Science
Plant-derived sustainable fuel sources could contribute to
near-term U.S. energy security and independence. However, weather conditions
could greatly affect crop yields. In this study, researchers examined the
effect of weather on biofuel production by comparing switchgrass and corn
stover harvested after a year of major drought and after 2 years of normal
precipitation. They found that the plants produced more sugar, but the sugar
changed during pretreatment and produced toxic compounds rather than the
desired fuels.
The Impact
The study is the first linking changes in rainfall and other
conditions during crop growth to potential detrimental effects on biofuels. The
work underscores the need to develop production systems that can tolerate
sugars produced under stress and turn those sugars into the desired biofuels.
Summary
In response to the 2012 severe Midwestern drought, soluble
sugar accumulated in switchgrass at significantly higher levels in comparison
to non-drought years. The sugars were chemically changed during the
pretreatment stage, the step that opens up the physical structure of the plant
cell wall. The soluble sugars chemically changed by reacting with the
ammonia-based pretreatment chemicals to form highly toxic compounds known as imidazoles
and pyrazines. The formation of toxic compounds during the pretreatment stage
inhibited conversion, the final step where intermediates such as sugars are
fermented into biofuel by microorganisms, such as the microbe S.
cerevisiae. However, it may be possible to overcome this issue by 1)
removing the soluble sugars before pretreatment or 2) using microbial strains
resistant to the toxic effects of imidazoles and pyrazines. This study
demonstrates that while there are benefits to growing bioenergy crops on
marginal lands to avoid competition with food crops, the plants grown there may
experience higher levels of stress resulting in deleterious impacts on microbes
during biofuel production. To develop sustainable biofuel production systems,
the deleterious effects of stress, such as fluctuations in precipitation and
water availability, must be mitigated. This research helps to provide an
understanding of the effects of drought stress on switchgrass.
Funding
This work was funded by the U.S. Department of Energy (DOE)
Great Lakes Bioenergy Research Center (DOE Office of Science, Biological and
Environmental Research, DE-FC02-07ER64494). Additional funding for L.G.O. was
provided by the DOE American Recovery and Reinvestment Act Sustainability
Initiative for Great Lakes Bioenergy Research Center (subcontract 109044 under
DE-AC05-76RLO1830 to Pacific Northwest National Laboratory).
Comments
Post a Comment