Tengborg C, Galbe M, Zacchi G
Department of Chemical Engineering 1, Lund University, PO Box 124, SE-221 00 Lund, Sweden.
Biotechnol Prog. 2001 Jan-Feb;17(1):110-7. doi: 10.1021/bp000145+.
Softwood is an interesting raw material for the production of fuel ethanol as a result of its high content of hexoses, and it has attracted attention especially in the Northern hemisphere. However, the enzymatic hydrolysis of softwood is not sufficiently efficient for the complete conversion of cellulose to glucose. Since an improvement in the glucose yield is of great importance for the overall economy of the process, the influence of various parameters on the cellulose conversion of steam-pretreated spruce has been investigated. The addition of beta-glucosidase up to 50 IU g(-)(1) cellulose to the enzymatic hydrolysis process resulted in increased cellulose conversion at a cellulase loading up to 48 FPU g(-)(1) cellulose. Despite very high enzyme loading (120 FPU g(-)(1) cellulose) only about 50% of the cellulose in steam-pretreated spruce was converted to glucose when all of the material following pretreatment was used in the hydrolysis step. The influence of temperature, residence time, and pH were investigated for washed pretreated spruce at a dry matter (DM) content of 5% and a cellulase activity of 18.5 FPU g(-)(1) cellulose. The optimal temperature was found to be dependent on both residence time and pH, and the maximum degree of cellulose conversion, 69.2%, was obtained at 38 degrees C and pH 4.9 for a residence time of 144 h. However, when the substrate concentration was changed from 5% to 2% DM, the cellulose conversion increased to 79.7%. An increase from 5% to 10% DM resulted, however, in a similar degree of cellulose conversion, despite a significant increase in the glucose concentration from 23 g L(-)(1) to 45 g L(-)(1). The deactivation of beta-glucosidase increased with increasing residence time and was more pronounced with vigorous agitation.
软木因其己糖含量高，是生产燃料乙醇的一种有趣的原料，尤其在北半球受到关注。然而，软木的酶水解对于将纤维素完全转化为葡萄糖的效率并不足够高。由于提高葡萄糖产率对该工艺的整体经济性至关重要，因此研究了各种参数对蒸汽预处理云杉纤维素转化的影响。在酶水解过程中添加高达50 IU g⁻¹纤维素的β-葡萄糖苷酶，在纤维素酶负载量高达48 FPU g⁻¹纤维素时，纤维素转化率提高。尽管酶负载量非常高（120 FPU g⁻¹纤维素），但当预处理后的所有物料用于水解步骤时，蒸汽预处理云杉中只有约50%的纤维素转化为葡萄糖。研究了温度、停留时间和pH对洗涤后的预处理云杉在干物质（DM）含量为5%和纤维素酶活性为18.5 FPU g⁻¹纤维素时的影响。发现最佳温度取决于停留时间和pH，在38℃和pH 4.9、停留时间为144 h时，纤维素转化率最高可达69.2%。然而，当底物浓度从5% DM变为2% DM时，纤维素转化率提高到79.7%。然而，从5% DM增加到10% DM，尽管葡萄糖浓度从23 g L⁻¹显著增加到45 g L⁻¹，但纤维素转化率相似。β-葡萄糖苷酶的失活随着停留时间的增加而增加，并且在剧烈搅拌时更明显。
