Lignin valorization through integrated biological funneling and chemical catalysis
Lignin valorization through integrated biological funneling and chemical catalysis
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DOI：
10.1073/pnas.1410657111
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发表时间：
2014-08-19
影响因子：
11.1
通讯作者：
Beckham, Gregg T.
中科院分区：
文献类型：
--
作者：
Linger, Jeffrey G.;Vardon, Derek R.;Beckham, Gregg T.
木质素是一种能量密度高的非均相聚合物，由植物用于结构、水分运输和防御的苯丙素单体组成，是地球上仅次于纤维素的第二大生物聚合物。在从生物质生产燃料和化学品中，木质素通常未充分用作原料并燃烧用于工艺热，因为其固有的异质性和不均匀性使得难以选择性地增值。然而，在自然界中，一些生物体已经进化出能够利用木质素衍生的芳族分子作为碳源的代谢途径。芳香族催化剂通常通过充当“生物漏斗”的上部途径发生，以将异质底物转化为中心中间体，如原儿茶酸盐或儿茶酚。这些中间体经历环裂解，并通过β-酮己二酸途径进一步转化为中心碳代谢。在这里，我们使用一种天然的芳香族分解代谢生物体，恶臭假单胞菌KT 2440，证明这些芳香族代谢途径可用于将芳香族模型化合物和来自中试规模生物质预处理的异构的富含木质素的流转化为中链长度的聚羟基烷酸酯（mcl-PHA）。然后从细胞中分离mcl-PHA，并证明其在物理化学性质上与常规的碳水化合物衍生的mcl-PHA相似，其具有作为生物塑料的应用。在其效用的进一步证明中，mcl-PHA被催化转化为化学前体和燃料范围的烃。总的来说，这项工作表明，芳香族分解代谢途径的使用能够通过克服其固有的异质性来生产燃料，化学品和材料，从而使木质素增值。
Lignin is an energy-dense, heterogeneous polymer comprised of phenylpropanoid monomers used by plants for structure, water transport, and defense, and it is the second most abundant biopolymer on Earth after cellulose. In production of fuels and chemicals from biomass, lignin is typically underused as a feed-stock and burned for process heat because its inherent heterogeneity and recalcitrance make it difficult to selectively valorize. In nature, however, some organisms have evolved metabolic pathways that enable the utilization of lignin-derived aromatic molecules as carbon sources. Aromatic catabolism typically occurs via upper pathways that act as a "biological funnel" to convert heterogeneous substrates to central intermediates, such as protocatechuate or catechol. These intermediates undergo ring cleavage and are further converted via the beta-ketoadipate pathway to central carbon metabolism. Here, we use a natural aromatic-catabolizing organism, Pseudomonas putida KT2440, to demonstrate that these aromatic metabolic pathways can be used to convert both aromatic model compounds and heterogeneous, lignin-enriched streams derived from pilot-scale biomass pretreatment into medium chain-length polyhydroxyalkanoates (mcl-PHAs). mcl-PHAs were then isolated from the cells and demonstrated to be similar in physicochemical properties to conventional carbohydrate-derived mcl-PHAs, which have applications as bioplastics. In a further demonstration of their utility, mcl-PHAs were catalytically converted to both chemical precursors and fuel-range hydrocarbons. Overall, this work demonstrates that the use of aromatic catabolic pathways enables an approach to valorize lignin by overcoming its inherent heterogeneity to produce fuels, chemicals, and materials.