The integration of first- and second-generation bioethanol processes has the potential to accelerate the establishment of second-generation bioethanol on the market. Cofermenting pretreated wheat straw with a glucose-rich process stream, such as wheat grain hydrolysate, in a simultaneous saccharification and fermentation process could address the technical issues faced during the biological conversion of lignocellulose to ethanol. For example, doing so can increase the final ethanol concentration in the broth and mitigate the effects of inhibitors formed during the pretreatment. Previous research has indicated that blends of first- and second-generation substrates during simultaneous saccharification and fermentation have synergistic effects on the final ethanol yield, an important parameter in the process economy. In this study, enzymatic hydrolysis and simultaneous saccharification and fermentation were examined using blends of pretreated wheat straw and saccharified wheat grain at various ratios. The aim of this study was to determine the underlying mechanisms of the synergy of blending with regard to the yield and volumetric productivity of ethanol. Replacing 25% of the pretreated wheat straw with wheat grain hydrolysate during simultaneous saccharification and fermentation was sufficient to decrease the residence time needed to deplete soluble glucose from 96 to 24 h and shift the rate-limiting step from ethanol production to the rate of enzymatic hydrolysis. Further, a synergistic effect on ethanol yield was observed with blended substrates, coinciding with lower glycerol production. Also, blending substrates had no effect on the yield of enzymatic hydrolysis. The effects of substrate blending on the volumetric productivity of ethanol were attributed to changes in the relative rates of cell growth and cell death due to alterations in the concentrations of substrate and pretreatment-derived inhibitors. The synergistic effect of substrate blending on ethanol yield was attributed in part to the decreased production of cell mass and glycerol. Thus, it is preferable to perform simultaneous saccharification and fermentation with substrate blends rather than pure substrates with regard to yield, productivity, and the robustness of the process.

中文翻译：

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通过混合原料提高乙醇产量和提高生产可预测性的策略。

第一代和第二代生物乙醇工艺的整合有可能加速第二代生物乙醇在市场上的建立。在同时糖化和发酵过程中将预处理的小麦秸秆与富含葡萄糖的工艺流（如小麦籽粒水解物）共同发酵可以解决木质纤维素生物转化为乙醇过程中面临的技术问题。例如，这样做可以增加肉汤中的最终乙醇浓度，并减轻预处理过程中形成的抑制剂的影响。先前的研究表明，在同时糖化和发酵过程中，第一代和第二代底物的混合物对最终的乙醇产量具有协同效应，这是工艺经济性的一个重要参数。在这项研究中，使用不同比例的预处理小麦秸秆和糖化小麦籽粒的混合物检查酶促水解和同时糖化和发酵。本研究的目的是确定混合对乙醇产量和体积生产率的协同作用的潜在机制。在同时糖化和发酵过程中用小麦籽粒水解物代替 25% 的预处理小麦秸秆足以将消耗可溶性葡萄糖所需的停留时间从 96 小时减少到 24 小时，并将限速步骤从乙醇生产转变为酶水解速率. 此外，观察到混合底物对乙醇产量的协同作用，与较低的甘油产量相吻合。此外，混合底物对酶水解的产率没有影响。底物混合对乙醇体积生产率的影响归因于由于底物和预处理衍生抑制剂浓度的变化导致细胞生长和细胞死亡的相对速率发生变化。底物混合对乙醇产量的协同作用部分归因于细胞团和甘油的产生减少。因此，就产量、生产率和过程的稳健性而言，优选使用底物混合物而不是纯底物进行同时糖化和发酵。底物混合对乙醇产量的协同作用部分归因于细胞团和甘油的产生减少。因此，就产量、生产率和过程的稳健性而言，优选使用底物混合物而不是纯底物进行同时糖化和发酵。底物混合对乙醇产量的协同作用部分归因于细胞团和甘油的产生减少。因此，就产量、生产率和过程的稳健性而言，优选使用底物混合物而不是纯底物进行同时糖化和发酵。