木质素芳香族化合物降解菌Sphingobium sp. SYK-6的研究进展

Recent advances in Sphingobium sp． SYK-6 for lignin aromatic compounds degradation-A review

摘要:

摘要:木质素是木质的主要成分之一，在自然界中，高分子木质素被真菌的胞外酶分解成低分子芳香族化合物，然后土壤细菌将其完全降解为二氧化碳。由此可见，木质素的完全降解过程是真菌和细菌的共同作用。研究细菌的降解机制，一方面可以理解芳香族化合物在生态系中的碳素循环，另一方面可以为木质素的有效利用提供基因和酶工具，将可再生资源的木质素转化成高附加价值的工业产品。Sphingobium sp. SYK-6是1987年从造纸厂废水中以木质素中的联苯化合物(5，5’-脱氢联香草酸)作为唯一碳源分离出的木质素化合物降解菌。在长达25年以上的研究中我们阐明了一系列芳香族化合物的代谢途径，克隆了相关基因，2012年随着基因组测序的完成，整个降解功能的全貌展现出来。介绍内容:(1)基因组信息;(2)芳醚化合物代谢;(3)联苯化合物代谢;(4)阿魏酸代谢;(5)木质素化合物降解过程中四氢叶酸依赖型机制;(6)原儿茶酸4，5开环途径;(7)3-甲氧基没食子酸代谢的多样性;(8)应用研究。我们希望SYK-6 菌株成为一个让人们理解木质素化合物降解的模式菌株。最后结合课题组现在的研究课题展望了木质素化合物的降解研究的发展方向。

Abstract:

Abstract:Lignin is complex heteropolymer produced from hydroxycinnamyl alcohols through radical coupling．In nature，white-rot fungi are assumed initially to attack native lignin and release lignin-derived-low-molecular-weight compounds，and soil bacteria play an importent role for completely degradation of these compounds．Study on the soil bacteria degrading lignin-derived-low-molecular-weight compounds will give way to understand how aromatic compounds recycle in nature，and to utilize lignin compounds as the renewable materials for valuable materials production． Sphingobium sp．SYK-6 that grows on lignin biphenyl (5，5’-dehydrodivanillate) had been isolated from pulp effluent in 1987．We have researched this bacterium more than 25 years，a serious aromatic metabolic pathway has been determined，and related genes have been isolated．As the complete genome sequence of SYK-6 has been opened to the public in 2012，the entire aromatic compounds degradation mechanisms become more clear．Main contents in our review cover: (1) genome information; (2) aryl metabolism; (3) biphenyl metabolism; (4) ferulate metabolism; (5) tetrahydrofolate-dependent O-demethylation system for lignin compound degrdation; (6) protocatechuate 4，5-cleavage pathway; (7) multiple pathways for 3-O-methylgallate metabolism．