Production of biofuels from inedible parts such as rice straw is so far not economically viable. Researchers in Japan suggest alternative approaches to overcome the difficulties.
Ethanol made from biomass (bioethanol), has become an increasingly popular alternative to gasoline. However, the production of bioethanol from food crops such as grains (first generation biofuels) has resulted in competition with food. Researchers around the world therefore are trying to find ways to produce bioethanol from non-food plants (second generation biofuels) or biomass waste such as straw.
In the quest to produce second generation biofuels, researchers are faced with the problem to convert the raw biomass into sugars that can be easily converted into ethanol (so-called „soft carbohydrates“), such as grape sugar (glucose). Large parts of plant materials are made up of complex carbohydrates (such as cellulose or xylose) and are very robust. Therefore, the required methods to break them down into simple sugars which can be converted into biofuels are harsh, very costly or not yet commercially available.
Researchers around Dr. Ken Tokuyasu from the National Agriculture and Food Research Organisation (NARO) in Japan now present a new approach to use inedible plant materials such as straw as feedstock for biofuels. Their work was recently published in
Bioscience, Biotechnology and Biochemistry.
Dr. Tokuyasu’s team found that, contrary to the belief of many researchers, rice straw contains not only complex carbohydrates, but also the soft carbohydrates, such as starch and sucrose. Even more interesting was how they were able to develop an easy method to extract those sugars from rice straw.
Since the extraction of soft carbohydrates from rice straw has the potential to be an economically viable method of obtaining sugars for bioethanol production, Dr. Tokuyasu’s group suggests that research should focus further on this approach, and that more research is indeed needed.
Dr. Tokuyasu told Checkbiotech, “The largest challenge is to breed rice plants with large amounts of soft carbohydrates in their straw at maturity stage.” Rice straw from mature plants raised for the production of food and feed is regarded as a “byproduct” and can be used for the production of bioethanol.
As Dr. Tokuyasu emphasized, “Our new saccharification method would be feasible only when we recover adequate amounts of soft carbohydrates from rice straw at maturity stage.”
Dr. Tokuyasu also suggested that research should also continue to pursue another direction – find a way to completely use the potential of rice straw as a feedstock for bioethanol, while avoiding the methods of the second generation biofuels.
Checkbiotech learned that his advice is “to newly develop a third method which can be adapted to rice straw containing lignocellulose and moderate amounts of soft carbohydrates.” And the potential is not to be neglected. According to Dr. Tokuyasu, Japan alone could produce 2.6 billion liters of bioethanol per year from the accumulating rice straw.
Jeung-yil Park et al. Efficient recovery of glucose and fructose via enzymatic saccharification of rice straw with soft carbohydrates
. Bioscience, Biotechnology and Biochemistry, 73 (2009), doi: 10.1271/bbb.80840.
http://www.jstage.jst.go.jp/article/bbb/advpub/0/advpub_0904061389/_article
Dr. Ken Tokuyasu
National Food Research Institute
National Agriculture and Food Research Organization (NARO)
tokuyasu@affrc.go.jp
+81 29 838 7996
www.naro.affrc.go.jp/index_en.html
Eva Vojtech is a Science Journalist for Checkbiotech and has recently finished her doctorate in Environmental Sciences at the University of Zurich, Switzerland. Contact her at eva.vojtech@gmx.ch.
