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我所木质纤维素制乙醇研究工作取得新进展
我所木质纤维素制乙醇研究工作取得新进展
www.dicp.ac.cn    发布时间:2016-02-15 10:07    栏目类别:科技动态

        燃料乙醇是一种优质可再生的清洁能源,添加于汽油燃料里可替代部分石油基燃料并能降低污染物排放,已在国际上得到广泛使用。目前燃料乙醇主要依靠粮食淀粉和植物糖类为原料经发酵制得。利用来源广泛的农、林废弃物等各类木质纤维素为原料生产燃料乙醇有着极为广阔的前景,也是数十年来生物化工技术领域研究的一个焦点。木质纤维素制乙醇至少需要经过预处理、酶解、发酵三步完成,其中预处理过程中产生的毒性物质(如乙酸、糠醛、苯酚等)严重抑制酵母生长和乙醇发酵,成为纤维素乙醇生产的主要技术瓶颈。目前主要通过水洗、物理、化学和生物等方法对预处理木质纤维素及其酶解液进行深度脱毒才能实现较好的发酵效果。但是复杂的工艺、昂贵的设备投资、大量的水耗以及可发酵糖的损失等极大地降低了纤维素乙醇生产的经济效益,从而制约了纤维素乙醇的工业化进程。

       我所生物质转化技术研究组(DNL0602)张宗超研究团队在木质纤维素制乙醇研究工作中,发现聚乙二醇(PEG)与酵母细胞有很好的生物兼容性,而且PEG对工业酿酒酵母细胞(淀粉基)具有显著的外保护“原位脱毒”功能。这种化学分子的外保护使酵母细胞在与毒性物质共同存在时,仍具有将速生杨、玉米秸秆等木质纤维素水解液发酵生产乙醇的能力。研究结果表明,工业酿酒酵母(淀粉基)在PEG保护的条件下可直接将木质纤维素水解液转化为乙醇,无需进行基因改造、适应性培养。该方法可有效简化生产工艺、减少水耗和设备投资,推动纤维素乙醇的工业化进程。相关结果在线发表于近期的Scientific Reports(doi:10.1038/srep20361)上。
       (文/图 刘秀梅)

                     

Armored yeast cells produce cellulosic ethanol unharmed by toxic chemicals

Fuel ethanol in gasoline pumps around the world has been largely produced through biological fermentation from corn starch and plant sugars. Producing cellulosic ethanol from non-food feedstock such as agricultural and forest residues has encountered in decades serious challenges of bio-toxicity to fermentation microbes due to the presence of toxic chemicals. The processes of biomass pretreatment that are necessary to generate cellulosic sugars for ethanol production also inevitably generate toxic chemicals as byproducts. These chemicals significantly reduce the rates of yeast metabolism and the final ethanol titers in the fermentation step. Some detoxification techniques, including water washing, physical, chemical, and biological methods, increase capital investment and operational costs, and cause the loss of sugars.
A research team in the DNL 602 group, led by Professor Z. Conrad Zhang at the Dalian National Laboratory for Clean Energy, Dalian Institute of Chemical Physics, has developed an in-situ chemical detoxification process by adding polyethyleneglycol (PEG) that protects the yeast cells from harm by the toxic chemicals. In the presence of PEGs, the fermentation process becomes smooth with high ethanol yield by simply using a starch-base industrial S. cerevisiae. This work is now online published in the journal of Scientific Reports(doi:10.1038/srep20361
The PEG exo-protected yeast cells displayed remarkably improved ethanol productivity from a crudely pretreated lignocellulose sources such as poplar and corn stover. By adding PEGs, the starch-base industrial S. cerevisiae becomes directly applicable for the production of cellulosic ethanol without the need to use genetically modified microorganisms. This discovery allows simplified cellulosic ethanol production process with reduced capital investment. The research team is currently working on a scale up process for cellulosic ethanol production from several lignocellulosic feedstocks collected from the field.
“The PEG can be reused. The detoxification fermentation process largely improves the economics of cellulosic ethanol production.” Said Dr. Xiumei Liu, the lead author of the paper.
This work was funded by the Chinese Government “Thousand Talent” program funding.

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大连化学物理研究所 生物质转化技术研究组(DNL0602) 维护:姜宏