摘要
酸性亚氯酸钠法脱木素是目前实验室最常用的脱木素方法,可最大程度地保留综纤维素,但关于木质素在逐步脱除过程中其动力学及选择性的研究却很少。拉曼光谱能快速、定性和半定量地测定亚氯酸钠法脱木素过程中残余木质素及木质素单体含量在不同细胞及形态学区域的动态变化。以阔叶材桉木、针叶材杉木、禾本科毛竹为例,通过提取亚氯酸钠法脱木素过程中不同细胞木质素(1598 cm^-1)及单体愈疮木基(G,1270 cm^-1)、紫丁香基(S,1331 cm^-1)的平均拉曼光谱,发现三种木材在各区域中木质素脱除动力学总体规律一致,即在反应初期木质素大量快速移除,随着反应的进行木质素脱除效率下降。其中,在反应前0.5 h,1598 cm^-1处平均拉曼强度降低量超过82%,而在脱木素后期(1.0~1.5 h),木质素平均拉曼强度减少仅5%~15%。特别的,竹材脱木素所需时间要明显少于木材。相同条件下,竹材纤维细胞在前10 min内1598 cm^-1处拉曼强度减少就达88.65%。同时,木质素的脱除具有高度的选择性。在反应初期,射线细胞中G和S型木质素的移除率均高于导管和纤维细胞,而在导管、纤维细胞中,S型木质素的脱除比G型木质素更明显。在逐步脱除木质素过程中,导管、射线、纤维细胞间木质素相对强度关系总体不变,即导管、射线相对木质素浓度始终高于纤维细胞。总体而言,在组织水平,导管中木质素最难于脱除,射线细胞次之,纤维细胞中的木质素较容易脱除。在纤维细胞中,细胞角隅木质素脱除速率最高,其次是复合胞间层,次生壁最低。就木质素单体而言,S型木质素比G型木质素更容易脱除。研究表明拉曼光谱能简单、快速地检测不同树种中各类组织、细胞以及木质素结构单元在生物质化学预处理中残余木质素含量的动态变化,同时进一步加深对生物质亚氯酸钠法脱木素选择性及动力学的理解。
Acid-chlorite delignification is the most popular and established laboratory method for the lignin removal from biomass with only trace degradation of the polysaccharides.However,the information on delignification kinetics and selectivity at the cellular level as the reaction proceeds is limited.Raman microscopy can be used to determine the dynamic changes of residual lignin and lignin monomer content in different cells and morphological areas in the delignification process quickly,qualitatively and semi-quantitatively.The average Raman spectra at 1598,1270 and 1331 cm^-1 in different cells of eucalyptus(angiosperms),coniferous fir(angiosperms)and bamboo(grass)were extracted,which were attributed to lignin,guaiacyl units(G)and syringyl units(S),respectively.It wasfound that the rules of delignification kinetics in the three kinds of wood were consistent,namelya large amount of lignin was rapidly removed at the initial stage of the reaction,and the efficiency of lignin removal decreased with the reaction progress.At the first 0.5 h,the average Raman intensity at 1598 cm^-1 decreased more than 82%,while only 5%~15%of the average Raman intensity was decreased at the later stage of delignification.Particularly,the bamboo took significantly less delignification time than the wood under the same condition,which the Raman intensity at 1598 cm^-1 of bamboo fiber decreased more than 88.65%within the first 10 minutes.Meanwhile,lignin removal was highly selective.At the initial stage of reaction,the removal rate of G and S lignin in ray cells was higher than that in the vessel and fiber cells,and in vessel and fiber cells more S lignin were removed than G lignin.In the whole process,the vessel was the most resistant to delignification,followed by ray and less resistant in fiber.In morphologically various areas,therate of lignin removal of the cell corner was the highest,followed by the compound middle lamella,and then the secondary wall of fiber.For lignin monomers,the S units were more prone to being removed than G units.The result showed that Raman spectroscopy could be used to detect the dynamic changes of residual lignin content in different tree species,tissues,cells and lignin units during the gradual delignification process,which could help to further understanding the selectivity and dynamics of delignification.
作者
金克霞
江泽慧
马建锋
田根林
杨淑敏
尚莉莉
冯龙
刘杏娥
JIN Ke-xia;JIANG Ze-hui;MA Jian-feng;TIAN Gen-lin;YANG Shu-min;SHANG Li-li;FENG Long;LIU Xing-e(International Centre for Bamboo and Rattan,Key Lab of Bamboo and Rattan Science&Technology,Beijing 100102,China)
出处
《光谱学与光谱分析》
SCIE
EI
CAS
CSCD
北大核心
2020年第9期2951-2956,共6页
Spectroscopy and Spectral Analysis
基金
国家“十三五”重点研发计划项目(2017YED0600804)
国际竹藤中心基本科研业务费项目(1632017014)
国家自然科学基金项目(31670565)资助。
关键词
木质素脱除
拉曼光谱
细胞壁
木质素单体
Delignification
Raman spectroscopy
Cell wall
Lignin monomers
