杨木稀酸预处理液木糖发酵产乙醇工艺条件的研究
Study on the Processing Conditions of Xylose Fermentation to Produce Fuel Ethanol from Dilute-acid Pretreated Poplar
-
摘要: 以1.0% H2SO4在150℃预处理杨木屑20min可水解溶出66.5%木聚糖和7.1%葡聚糖,生成以木糖为主、含有乙酸和甲酸等发酵抑制物的预处理液,脱毒后可采用Candida shehatae R发酵产乙醇,而Pichia stipitis NL23不能生长。减压蒸发加石灰中和法对预处理液的脱毒效果最佳,可脱除70.0%乙酸和40.0%甲酸,糖损失仅为5.0%~6.0%, C.shehatae R的耗糖率和乙醇得率可达到93.2%和83.6%。采用廉价的无机盐能够满足C.shehatae R发酵脱毒液的营养要求。由于包括乙酸和甲酸以外其它毒性物的抑制,C.shehatae R发酵脱毒液的适宜糖质量浓度为30.0g/L,发酵12h,耗糖率和乙醇得率为84.7%和75.3%,乙醇质量浓度达到最高值8.54g/L,同时生成6.08g/L木糖醇,C.shehatae R对木糖的利用未受葡萄糖的抑制。Abstract: Xylose solution containing acetate, formate and other fermentation inhibitors was obtained from dilute-acid pretreated poplar sawdust steeped with 1.0% sulfuric acid for 20min at 150℃, from which 66.5% xylan and 7.1% glucosan in poplar were hydrolyzed into soluble xylose and glucose. Some detoxication treatment is necessary for Candida shehatae R to ferment this solution to produce ethanol, but even so it was still deadly for the growth of Pichia stipitis NL23. Over 70.0% acetate and 40.0% formate were removed, while the loss of xylose and glucose was only 5.0%-6.0% simultaneously, when the process of vacuum evaporation followed by lime powder neutralization was used for cleaning the solution as an optimal detoxication technique. After detoxication, C.shehatae R was able to utilize 93.2% sugar and the ethanol yield reached 83.6%. Low-cost inorganic salts could supply the nutriments for growth and fermenting of C.shehatae R in the detoxicated solution (DS). The optimal initial mass concentration of DS for C.shehatae R fermentation to produce ethanol is 30.0g/L sugar because of inhibitors besides acetate and formate. The strain could use 84.7% sugar to produce 8.54g/L ethanol at the yield of 75.3% together with 6.08g/L xylitol after 12h of culture. The glucose-inhibition effect on xylose fermentation was not detected for fermenting DS into ethanol by C.shehatae R.