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酶在生产纤维素乙醇过程中是一项重要支出,只要保证乙醇的产量和生产力不降低,减少酶的使用将是有价值的。该项研究旨在评估酶剂量对纤维素向乙醇转化过程的影响。牛皮纸浆,是纸生产过程的一种中间产物,用来代表分离出来的纤维素原料。实验在一个5L(工作体积为2-3L)的流动式生物反应器中进行,并以80～900r/min范围内不断变化的搅拌速度使之充分混合。通过查阅文献,计算出纤维素酶的平均剂量为每克葡聚糖34FPU和β-葡糖苷酶的平均剂量为每克葡聚糖135CBU,并将之设定为100%剂量。实验选用了酶剂量分别为1%,7%,13%,33%,67%,100%,133%,在干重为4.8%的牛皮纸浆悬浮液中使用纤维素酶NovozymeCelluclast1.5L和β-葡糖苷酶Novozyme188。Novozyme酶的剂量选用其推荐范围的最低值:在浓度为12g/g的葡聚糖中加入Celluclast1.5L35%的剂量,在浓度为1.2g/g的葡聚糖中加入Novozyme1880.9%的剂量。在50℃时的糖化实验显示了一个典型的剂量反应:酶剂量为133%时糖浓度达到最高(约每升葡萄糖59克),糖化速度为2.45g/L/h,该条件下出现一个特定的糖化速度为每小时每个酶单位2.2×10-4克葡萄糖。然而,酶剂量为13%时最高的糖化速度为每小时每个酶单位2.9×10-4克葡萄糖。在35℃时进行同步糖化发酵实验,用酿酒酵母或假丝酵母比较33%,67%,100%,和133%的酶剂量。酶剂量为67%时或多于文献中的平均酶剂量时,乙醇浓度和生产率相似,然而在酶剂量为33%时乙醇浓度和生产率更低。因此,在保证乙醇的产量和生产率不降低的情况下,酶剂量可显著降低至文献中引用的典型水平以下,但不能降低到制造商推荐的水平。
Enzymes are an important expense in the process of producing cellulosic ethanol, as long as the yield and productivity of ethanol are not reduced, reducing the use of enzymes will be valuable. The study was designed to evaluate the effect of enzyme dosage on the conversion of cellulose to ethanol. Kraft pulp, an intermediate product of paper production, is used to represent the separated cellulosic raw material. The experiments were carried out in a 5 L (working volume 2-3 L) flow bioreactor and thoroughly mixed at a constant stirring speed in the range of 80-900 rpm. By consulting the literature, the average dosage of cellulase was calculated to be 34 FPU per gram of dextran and an average dose of 135 CBU per gram of dextran set at 100% dose. In the experiments, cellulase Novozyme Celluclast1.5L andβ-lactone were used in the kraft pulp suspension with the dry weight of 4.8% at the dosage of 1%, 7%, 13%, 33%, 67%, 100% and 133% Glucosidase Novozyme188. The dose of Novozyme enzyme was selected to be the lowest of its recommended range: Celluclast 1.5 L 35% was added to dextran at a concentration of 12 g / g and Novozyme 1880.9% at a concentration of 1.2 g / g dextran . The saccharification experiments at 50 ° C showed a typical dose response: the highest sugar concentration was obtained at 133% enzyme dosage (about 59 g glucose per liter), the saccharification rate was 2.45 g / L / h, and under this condition a specific dose The saccharification rate is 2.2 x 10 <-4> g glucose per enzyme unit per hour. However, the highest saccharification rate at 13% enzyme dosage was 2.9 x 10 "4 grams of glucose per enzyme unit per hour. Simultaneous saccharification and fermentation experiments were performed at 35 ° C with 33%, 67%, 100%, and 133% enzyme doses compared to S. cerevisiae or Candida. Ethanol concentration and productivity were similar at 67% enzyme enzyme or more than the average enzyme dose in the literature, whereas ethanol concentration and productivity were lower at enzyme dose of 33%. Thus, the enzyme dosage can be significantly reduced below the typical levels quoted in the literature, without diminishing the yield and productivity of ethanol, but not to the manufacturer’s recommended level.