成果報告書詳細
管理番号20100000001514
タイトル*平成21年度中間年報 新エネルギー技術研究開発 バイオマスエネルギー等高効率転換技術開発(先導技術開発) 新規エタノール発酵糸状菌を活用した稲わら等の同時糖化発酵システムの開発
公開日2010/9/30
報告書年度2009 - 2009
委託先名国立大学法人富山大学 富山県立大学
プロジェクト番号P07015
部署名新エネルギー技術開発部
和文要約和文要約等以下本編抜粋:1. 研究開発の内容及び成果等 我が国のような貧資源国では、稲わらなどのバイオマス資源を効率よくエタノールへ変換させるための技術開発は極めて重要である。そこで、稲作から廃棄物として発生する稲わらなどからエタノールを生産する際のエネルギー投入量を軽減させることを目的として、新規な糸状菌を活用した同時糖化発酵システムを構築し、稲わらなどからエタノールを効率よく生産させることを検討した。
英文要約Title: New Energy Technology Development/Development to Technology for High-efficiency Conversion of Biomass and Other Energy. Development of SSCF System to Produce Ethanol from Rice Straw Using Novel Ethanol-fermenting Fungi (FY2008-FY2011) FY2009 Annual Reports.
In order to reduce the energy inputs required to efficiently produce ethanol from biomass such as rice straw generated from rice farming as agricultural residue, a simultaneous saccharification and cofermentation (SSCF) system that will use novel fungi is being constructed in this R&D project. In 2009, the following subtheme was investigated: (1) re-screening and evaluation of characteristics of ethanol-fermenting fungi, (2) research of pathway for metabolism and fermentation, (3) research of hydrolases secreted, (4) structural analysis of metabolism-related enzyme genes, and (5) development of SSCF. First, M.javanicas NBRC 4572 was mainly selected from about 150 spices of wild Mucor genus because the strain has the most excellent fermentative ability. Further, an ion-beam mutation was executed to the strain to improve the fermentation efficiency of xylose and then a mutant was obtained. The mutant has a high ethanol fermentation efficiency of 73% on xylose. Next, intracellular enzymes related to metabolism of xylose and ethanol fermentation in the mutant were biochemically investigated. As these results, it was found that the strain was able to be smoothly metabolized xylose and be fermented because the activities for xylose redactase (XR) and xylitol dehydrogenase (XDH) were higher than those of the wild strain and further the expression levels of pyruvate decarboxylase (PDC) and alcohol dehydrogenase (ADH) were larger than those of the wild strain. The maximum advantage of SSCF with the strain is to secrete a lot of hydrolases. When the fungi was cultured in the medium with rice straw, end-beta-glucosidase (EG), cellobiohydrolase (CBH), beta-glucosidase, xylanase (X), and beta-xylosidase (XB) were secreted and especially it was found that the secretion amounts of EG and X was larger than other enzymes. When the fungus was used from this fact, it was conformed to be able to reduce the usage of the cellulose in SSCF. In theme 4, to clarify the metabolism flow of the fungi (R.pusillus with ability of fermentation almost equal to M.javanicus) from xylose to ethanol, the clarification of function and structure by protein and the gene was investigated. XR, XDH, Glycerol dehydrogenase (GLD), and ADH were purified in the single by various chromatographies, respectively. These characters of molecular weight, subunit structure, substrate specificity etc. were clarified, respectively. It was discovered that the purified GLD was L-xylulose reductase (LXR) from the analytical result of the substrate-specificity and the amino acid sequence. As a result, the metabolism of D-xylose and L-arabinose to D-xylulose were clarified. Moreover, N-terminal and internal amino acid sequence of each enzyme were decided and from the information cDNA cloning from gDNA were done. Subsequently, the primary structures of purified enzymes were decided and it succeeded in appearance in the rearrangement E. coli, respectively. In theme 5, when the SSCF on rice straw prepared the steam-explosion method was carried out by combining 2 kinds of cellulase agents and the fungi, 22% of ethanol yield (ethanol concentration 8.5 g/L from 50 g/L rice straw) was able to be achieved in 36 h. Since the ethanol yield and the amount of ethanol production are still lows, it is necessary to improve the amount of ethanol production further by increasing the amount of cellulase that the fungus itself secretes, and optimizing the culture condition.
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