Biobutanol is promising and renewable alternative to traditional fossil fuels and could be produced by Clostridium species from lignocellulosic biomass. However, biomass is recalcitrant to be hydrolyzed into fermentable sugars attributed to the densely packed structure by layers of lignin. Development of pretreatment reagents and processes for increasing surface area, removing hemicellulose and lignin, and enhancing the relative content of cellulose is currently an area of great interest. Deep eutectic solvents (DESs), a new class of green solvents, are effective in the pretreatment of lignocellulosic biomass. However, it remains challenging to achieve high titers of total sugars and usually requires combinatorial pretreatment with other reagents. In this study, we aim to develop novel DESs with high application potential in biomass pretreatment and high biocompatibility for biobutanol fermentation. Several DESs with betaine chloride and ethylamine chloride (EaCl) as hydrogen bond acceptors were synthesized. Among them, EaCl:LAC with lactic acid as hydrogen bond donor displayed the best performance in the pretreatment of corncob. Only by single pretreatment with EaCl:LAC, total sugars as high as 53.5 g L−1 could be reached. Consecutive batches for pretreatment of corncob were performed using gradiently decreased cellulase by 5 FPU g−1. At the end of the sixth batch, the concentration and specific yield of total sugars were 58.8 g L−1 and 706 g kg−1 pretreated corncob, saving a total of 50% cellulase. Utilizing hydrolysate as carbon source, butanol titer of 10.4 g L−1 was achieved with butanol yield of 137 g kg−1 pretreated corncob by Clostridium saccharobutylicum DSM13864. Ethylamine and lactic acid-based deep eutectic solvent is promising in pretreatment of corncob with high total sugar concentrations and compatible for biobutanol fermentation. This study provides an efficient pretreatment reagent for facilely reducing recalcitrance of lignocellulosic materials and a promising process for biobutanol fermentation from renewable biomass.

中文翻译：

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通过新开发的用于生物丁醇发酵的乙胺基深共熔溶剂轻松降低木质纤维素生物质的顽固性

生物丁醇是传统化石燃料的有前途和可再生的替代品，并且可以由梭菌属物种从木质纤维素生物质生产。然而，生物质难以水解成可发酵的糖，这归因于木质素层的密集堆积结构。开发用于增加表面积、去除半纤维素和木质素以及提高纤维素相对含量的预处理试剂和工艺是目前备受关注的领域。低共熔溶剂（DESs）是一类新型绿色溶剂，可有效地预处理木质纤维素生物质。然而，要获得高滴度的总糖仍然具有挑战性，并且通常需要与其他试剂进行组合预处理。在这项研究中，我们的目标是开发在生物质预处理中具有高应用潜力和在生物丁醇发酵中具有高生物相容性的新型 DES。合成了几种以氯化甜菜碱和氯化乙胺 (EaCl) 作为氢键受体的 DES。其中以乳酸为氢键供体的EaCl:LAC在玉米芯的预处理中表现出最好的性能。仅通过 EaCl:LAC 的单一预处理，总糖可以达到高达 53.5 g L-1。使用梯度减少 5 FPU g-1 的纤维素酶进行连续批次的玉米芯预处理。在第六批结束时，总糖的浓度和比收率为 58.8 g L-1 和 706 g kg-1 预处理的玉米芯，总共节省了 50% 的纤维素酶。以水解物为碳源，丁醇效价为10。通过糖丁酸梭菌 DSM13864 预处理玉米芯，丁醇产量为 137 g kg-1，达到 4 g L-1。基于乙胺和乳酸的低共熔溶剂在高总糖浓度玉米芯的预处理中具有前景，并且与生物丁醇发酵相容。该研究提供了一种有效的预处理试剂，可轻松降低木质纤维素材料的顽固性，并为可再生生物质发酵生物丁醇提供了一种有前景的工艺。