State Key Laboratory of Tree Genetics and Breeding, Northeast Forestry University, Harbin, China; State Key Laboratory of Tree Genetics and Breeding, Chinese Academy of Forestry, Beijing, China.
Plant Biotechnol J. 2014 Dec;12(9):1174-92. doi: 10.1111/pbi.12273. Epub 2014 Oct 20.
Lignocelluloses from plant cell walls are attractive resources for sustainable biofuel production. However, conversion of lignocellulose to biofuel is more expensive than other current technologies, due to the costs of chemical pretreatment and enzyme hydrolysis for cell wall deconstruction. Recalcitrance of cell walls to deconstruction has been reduced in many plant species by modifying plant cell walls through biotechnology. These results have been achieved by reducing lignin content and altering its composition and structure. Reduction of recalcitrance has also been achieved by manipulating hemicellulose biosynthesis and by overexpression of bacterial enzymes in plants to disrupt linkages in the lignin-carbohydrate complexes. These modified plants often have improved saccharification yield and higher ethanol production. Cell wall-degrading (CWD) enzymes from bacteria and fungi have been expressed at high levels in plants to increase the efficiency of saccharification compared with exogenous addition of cellulolytic enzymes. In planta expression of heat-stable CWD enzymes from bacterial thermophiles has made autohydrolysis possible. Transgenic plants can be engineered to reduce recalcitrance without any yield penalty, indicating that successful cell wall modification can be achieved without impacting cell wall integrity or plant development. A more complete understanding of cell wall formation and structure should greatly improve lignocellulosic feedstocks and reduce the cost of biofuel production.
植物细胞壁中的木质纤维素是可持续生物燃料生产的有吸引力的资源。然而，由于细胞壁的化学预处理和酶解用于细胞解构的成本较高，将木质纤维素转化为生物燃料比其他现有技术更昂贵。通过生物技术对植物细胞壁进行修饰，可以降低许多植物物种细胞壁的抗降解性。这些结果是通过降低木质素含量并改变其组成和结构来实现的。通过操纵半纤维素生物合成和在植物中过表达细菌酶来破坏木质素-碳水化合物复合物中的键，也可以降低抗降解性。这些经过修饰的植物通常具有更高的糖化产率和更高的乙醇产量。细菌和真菌的细胞壁降解（CWD）酶已在植物中高水平表达，以提高糖化效率，与外源性添加纤维素酶相比。来自细菌嗜热菌的耐热 CWD 酶在植物中的表达使自水解成为可能。可以对转基因植物进行工程改造以降低抗降解性而不会造成任何产量损失，这表明无需影响细胞壁完整性或植物发育即可成功进行细胞壁修饰。对细胞壁形成和结构的更全面了解应能大大改善木质纤维素原料，并降低生物燃料生产的成本。
