Ammonia-salt solvent promotes cellulosic biomass deconstruction under ambient pretreatment conditions to enable rapid soluble sugar production at ultra-low enzyme loadings
Ammonia-salt solvent promotes cellulosic biomass deconstruction under ambient pretreatment conditions to enable rapid soluble sugar production at ultra-low enzyme loadings
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DOI：
10.1039/c9gc03524a
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发表时间：
2020-01-07
期刊：
影响因子：
9.8
通讯作者：
Pingali, Sai Venkatesh
中科院分区：
文献类型：
--
作者：
Chundawat, Shishir P. S.;Sousa, Leonardo da Costa;Pingali, Sai Venkatesh
在这里，我们报告了一种新的氨：铵盐溶剂为基础的预处理工艺，可以快速溶解结晶纤维素到溶液中，并最终在近环境条件下生产高度无定形纤维素。在环境温度下，预激活纤维素I异位形态为氨-纤维素膨胀复合物（或纤维素III异位形态），有助于在环境压力下，预激活的纤维素在氨-盐溶剂（即溶解在液氨中的硫氰酸铵盐）中快速溶解。在文献报道中，我们首次使用时间分辨原位中子散射方法来表征纤维素多晶型的结构修饰，并了解结晶纤维素在氨盐溶剂下溶解到“分子”溶液中的实时机制。我们还使用分子动力学模拟来深入了解非共价破坏纤维素氢键网络的溶剂相互作用，并了解这些溶剂如何能够快速完全溶解预活化的纤维素III。重要的是，预处理后回收的再生无定形纤维素所需的纤维素酶用量比天然晶体纤维素少50倍，以实现几乎完全的水解转化为可溶性糖。最后，我们提供了概念验证结果，进一步展示了这种氨盐溶剂如何在环境处理条件下预处理和分馏木质纤维素生物质（如玉米秸秆），同时选择性地共提取约80-85%的总木质素，以生产高度可消化的富含多糖的生物炼制原料。与传统的氨基预处理工艺（例如氨纤维膨胀或萃取氨预处理）不同，所提出的氨盐工艺可以在近环境条件下运行，大大降低了对木质纤维素进行有效氨基预处理所需的压力/温度严重性。
Here, we report a novel ammonia : ammonium salt solvent based pretreatment process that can rapidly dissolve crystalline cellulose into solution and eventually produce highly amorphous cellulose under near-ambient conditions. Pre-activating the cellulose I allomorph to its ammonia-cellulose swollen complex (or cellulose III allomorph) at ambient temperatures facilitated rapid dissolution of the pre-activated cellulose in the ammonia-salt solvent (i.e., ammonium thiocyanate salt dissolved in liquid ammonia) at ambient pressures. For the first time in reported literature, we used time-resolved in situ neutron scattering methods to characterize the cellulose polymorphs structural modification and understand the mechanism of crystalline cellulose dissolution into a 'molecular' solution in real-time using ammonia-salt solvents. We also used molecular dynamics simulations to provide insight into solvent interactions that non-covalently disrupted the cellulose hydrogen-bonding network and understand how such solvents are able to rapidly and fully dissolve pre-activated cellulose III. Importantly, the regenerated amorphous cellulose recovered after pretreatment was shown to require nearly similar to 50-fold lesser cellulolytic enzyme usage compared to native crystalline cellulose I allomorph for achieving near-complete hydrolytic conversion into soluble sugars. Lastly, we provide proof-of-concept results to further showcase how such ammonia-salt solvents can pretreat and fractionate lignocellulosic biomass like corn stover under ambient processing conditions, while selectively co-extracting similar to 80-85% of total lignin, to produce a highly digestible polysaccharide-enriched feedstock for biorefinery applications. Unlike conventional ammonia-based pretreatment processes (e.g., Ammonia Fiber Expansion or Extractive Ammonia pretreatments), the proposed ammonia-salt process can operate at near-ambient conditions to greatly reduce the pressure/temperature severity necessary for conducting effective ammonia-based pretreatments on lignocellulose.