Essential Requirements of Biocompatible Cellulose Solvents
Essential Requirements of Biocompatible Cellulose Solvents
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DOI：
10.1021/acssuschemeng.1c03438
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发表时间：
2021-08-25
影响因子：
8.4
通讯作者：
Kuroda, Kosuke
中科院分区：
文献类型：
--
作者：
Komori, Tetsuo;Satria, Heri;Kuroda, Kosuke
从植物生物质中生产节能生物乙醇的需求很大，迄今为止报道的最有前途的方法之一是一锅乙醇生产，即在同一反应釜中从生物质中生产乙醇，例如工业第一代生物乙醇。这个过程需要对发酵微生物毒性极低的纤维素溶剂。在此，我们开发了一种低毒的两性离子纤维素溶剂，称为4-(1-（2-（2-甲氧基乙氧基）乙基）咪唑-3-io)-丁酸酯(OE（2)imC(3)C）。OE(2)imC(3)C是唯一报道的满足以下性质的溶剂：在温和的温度下是液体，具有良好的纤维素溶解能力和低毒性，即使包括其他类型的溶剂。本文通过合成22种两性离子，研究了它们的化学结构与性能之间的关系。长烷基或低聚醚链连接到阳离子（阳离子尾巴）是必要的是液体。除带有辛烷尾的雌雄同体外，其余雌雄同体均表现出生物相容性。有趣的是，两性离子的间隔剂，即介于正离子和阴离子之间的烷基链，被认为是惰性的，但却影响了毒性。采用分子动力学方法对其分子机理进行了研究。毒性较低的两性离子很少将阳离子尾部插入细胞膜，因此不会使细胞膜破裂。离子液体具有自由阳离子和阴离子，可诱导细胞膜的分子水平破坏，这表明两性离子结构是低毒性的关键因素。这些间隔剂原本是惰性的，但却改变了溶剂团簇在体相中的结构，并导致了细胞膜的分子水平破坏。低毒纤维素溶剂的要求是两性离子结构，羧酸阴离子，长极性阳离子尾部，在某些情况下，短间隔。
Energy-efficient bioethanol production from plant biomass is in high demand, and one of the most promising procedures reported to date is one-pot ethanol production, that is, the production of ethanol from biomass in the same reaction pot, such as industrial first-generation bioethanol. This process requires cellulose solvents whose toxicity toward fermentative microorganisms is extremely low. Herein, we have developed a low-toxic zwitterionic cellulose solvent known as 4-(1-(2-(2-methoxyethoxy)ethyl)imidazol-3-io)-butyrate (OE(2)imC(3)C). OE(2)imC(3)C is the only reported solvent that satisfies the following properties: being liquid at mild temperature and having good cellulose dissolution ability and low toxicity, even when including other types of solvents. We here investigated the relationship between the chemical structures and properties by synthesizing 22 zwitterions. Long alkyl- or oligoether chains attached to the cation (cation tails) were necessary to be a liquid. The zwitterions, except for that with an octyl tail, exhibited biocompatibility. Interestingly, the spacers of the zwitterions, alkyl chains between the cations and anions, were expected to be inert, but affected the toxicity. The molecular mechanisms were investigated using molecular dynamics simulations. The zwitterions exhibiting low toxicity scarcely inserted their cation tails into cell membrane and thus did not rupture the cell membrane. Ionic liquids, which have free cations and anions, induced molecular-level disruption of the cell membrane, suggesting that the zwitterion structure is a critical factor for low toxicity. The spacers, which were expected to be inert, shifted the solvent cluster structures in the bulk phase and induced molecular-level disruption of the cell membrane. The requirements for low-toxic cellulose solvents are zwitterionic structures, carboxylate anions, long polar cation tails, and in some cases, short spacers.