Enzyme hydrolysis and ethanol fermentation of liquid hot water and AFEX pretreated distillers' grains at high-solids loadings
Enzyme hydrolysis and ethanol fermentation of liquid hot water and AFEX pretreated distillers' grains at high-solids loadings
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DOI：
10.1016/j.biortech.2007.09.031
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发表时间：
2008-08-01
影响因子：
11.4
通讯作者：
Dale, Bruce E.
中科院分区：
文献类型：
--
作者：
Kim, Youngrmi;Hendrickson, Rick;Dale, Bruce E.
干磨乙醇工业生产的主要副产品是酒糟，它由未水解和未发酵的聚合糖组成。利用酒糟作为可发酵糖的额外来源，有可能在当前的干法研磨过程中增加总体乙醇产量。本研究采用控制pH值的液体热水预处理(LHW)和氨纤维膨化(AFEX)处理来提高酒糟的酶消化率。与未处理的原料相比，两种前处理方法均显著提高了酒糟干物质(DDGS)的水解率，当每克葡聚糖的纤维素酶和β-葡萄糖苷酶的酶载量分别为15 fPU和40IU，固体载量为5%DDGS时，24 h内可将90%的纤维素转化为葡萄糖。在相同的酶作用下，以13-15%(干酒糟/总混合物重量)的固形物含量对处理后的湿酒糟进行水解，可使LHW和AFEX两种预处理的纤维素转化率降低到70%，并将转化时间延长到72h。当纤维素酶添加木聚糖酶和阿魏酸酯酶时，15%或20%固形物(w/w)的湿酒糟的葡萄糖得率为80%，木糖得率为50%。用非纤维素酶补充纤维素酶的原理由Dien等人在本杂志卷的后面部分给出。用葡萄糖发酵酿酒酵母ATCC 4124菌株发酵湿法酒糟，可使LHW和AFEX处理的湿法酒糟的理论酒精产率达到100%。发酵后残留的固形物具有显著较高的蛋白质含量，代表了蛋白质增强的湿DG，这将导致DDGS的增强。增强型DDGS指的是改进的干磨工艺的固体产品，在该工艺中，酒糟被回收并进一步加工，以提取未利用的聚合物糖。还介绍和讨论了实验室产生的增强型DDGS的成分变化。(C)2007爱思唯尔有限公司。保留所有权利。
The dry milling ethanol industry produces distiller's grains as major co-products, which are composed of unhydrolyzed and unfermented polymeric sugars. Utilization of the distiller's grains as an additional source of fermentable sugars has the potential to increase overall ethanol yields in current dry grind processes. In this study, controlled pH liquid hot water pretreatment (LHW) and ammonia fiber expansion (AFEX) treatment have been applied to enhance enzymatic digestibility of the distiller's grains. Both pretreatment methods significantly increased the hydrolysis rate of distiller's dried grains with solubles (DDGS) over unpretreated material, resulting in 90% cellulose conversion to glucose within 24 h of hydrolysis at an enzyme loading of 15 FPU cellulase and 40 IU beta-glucosidase per gram of glucan and a solids loading of 5% DDGS. Hydrolysis of the pretreated wet distiller's grains at 13-15% (wt of dry distiller's grains per wt of total mixture) solids loading at the same enzyme reduced cellulose conversion to 70% and increased conversion time to 72 h for both LHW and AFEX pretreatments. However, when the cellulase was supplemented with xylanase and feruloyl esterase, the pretreated wet distiller's grains at 15% or 20% solids (w/w) gave 80% glucose and 50% xylose yields. The rationale for supplementation of cellulases with non-cellulolytic enzymes is given by Dien et al., later in this journal volume. Fermentation of the hydrolyzed wet distiller's grains by glucose fermenting Saccharomyces cerevisiae ATCC 4124 strain resulted in 100% theoretical ethanol yields for both LHW and AFEX pretreated wet distiller's grains. The solids remaining after fermentation had significantly higher protein content and are representative of a protein-enhanced wet DG that would result in enhanced DDGS. Enhanced DDGS refers to the solid product of a modified dry grind process in which the distiller's grains are recycled and processed further to extract the unutilized polymeric sugars. Compositional changes of the laboratory generated enhanced DDGS are also presented and discussed. (C) 2007 Elsevier Ltd. All rights reserved.