适合鲜甘薯原料乙醇发酵的低粘度快速糖化预处理

Low Viscosity and Rapid Saccharification Pretreatment of Fresh Sweet Potato for Ethanol Production

甘薯是我国燃料乙醇生产的主要原料之一.但由于鲜甘薯具有粘度大的特点,传统液化糖化处理很难在短时间内充分糖化原料;高粘度的醪液也难以进行管道输送,容易堵塞管路;同时,也会降低后续的乙醇发酵效率.本文作者采用了快速粘度分析法对鲜甘薯糊化粘度特性进行了分析,进而对预处理条件进行了研究,考察了醪液的料水比、预处理温度、pH、时间、离子种类、酶类及添加方式对糖化醪液的葡萄糖值(Dextrose equivalent,DE)和粘度的影响.获得的最佳预处理条件为:料水比2:1,126℃、pH2.5条件下预处理5min,液化,糖化时加入果胶酶40U/g醪液,纤维素酶0.5U/g醪液.糖化2h后,醪液DE值最高可达99.3,粘度4.5×104mPa.s,而采用传统糖化工艺,糖化2h后,醪液DE值仅为85.8,粘度大于1.0×105mPa.s.此预处理方法也可用于快速糖化不加水的醪液.经预处理,糖化2h,醪液DE值可达97.6,而对照仅为76.6.后续的乙醇发酵试验表明,通过此预处理方法获得的糖化醪液对乙醇发酵无负面影响.

Sweet potato is one of the major feedstock for the fuel ethanol production in China. As fresh sweet potato syrup shows high viscosity, it is hard to be fully converted to glucose by enzymes in the traditional saccharification process. The high-viscosity syrup is difficult to be transmitted in pipes, which may be easily blocked. Meanwhile it could also reduce the efficency of later ethanol fermentation. To solve these problems, the pasting property of fresh sweet potato was studied by rapid visco analysis （RVA）. Effects of the pretreatment conditions including the ratio of material to water, temperature, pH, retention time, and kinds of icons and enzymes on the dextrose equivalent value （DE） and syrup viscosity were also investigated. The most favorable pretreatment conditions were the ratio of material to water 2：1, 126 ℃ for 5 min, pH 2.5. The amounts of pectinase and cellulose added in saccharification were 40 U per g syrup and 0.5U per g syrup, respectively. The highest DE of 99.3 and the lowest viscosity of 4.5×10^4 mPa.s were obtained by the most favorable pretreatment conditions, while those of 85.8 and over 1.0×10^5 mPa.s was produced by traditional treatment conditions. The pretreatment could also be applied for the material syrup without adding water, by which the DE could reach 97.6, higher than of 76.6 in normal process. The later experiments showed that it had no negative effect on the ethanol fermentation and exhibited lower viscosity. Fig 1, Tab 4, Ref 20