caa a22 4500 606207716 CHVBK 20210128101018.0 cr unu---uuuuu 210128e20150701xx s 000 0 eng 10.1007/s00425-015-2313-5 doi (NATIONALLICENCE)springer-10.1007/s00425-015-2313-5 The mechanism of xylans removal during hydrothermal pretreatment of poplar fibers investigated by immunogold labeling [Elektronische Daten] [Jing Ma, Zhe Ji, Jia Chen, Xia Zhou, Yoon Kim, Feng Xu] Main conclusion : Hydrothermal pretreatment initially removed the lignin-free xylan from the middle layer of secondary wall, followed by the lignin-bound xylan, but the cellulose-bound xylan was seldom removed by this pretreatment. An in-depth understanding of the mechanism of xylan removal during hydrothermal pretreatment (HTP) of wood is critical for cost-effective conversion of lignocellulosic biomass to biofuels. Several studies demonstrated the kinetics and mechanism of xylan removal during HTP on molecular scale, but the dissolution mechanism of xylan during HTP remains unclear at ultra-structural level. Our study investigated changes in the micro-distribution of xylan in poplar fiber cell walls during HTP by transmission electron microscopy (TEM) in combination with immunogold labeling. The study revealed that HTP caused greater decline in the density of xylan labeling in the S2 layer of fiber wall than in the S1 layer. There was a greater loss in the density of xylan labeling during HTP in the delignified and enzymatically treated fibers compared to untreated fibers. We propose that in the initial stages of HTP lignin-free xylan in the S2 layer was more readily hydrolyzed than in the S1 layer by hydronium ions. With increasing pretreatment time, the xylan covalently bound to lignin was also removed from the S2 layer due to the dissolution of lignin. The xylan tightly bound to cellulose was seldom removed during HTP, but was hydrolyzed in subsequent enzymatic treatment. This TEM-immunolabeling investigation reveals the manner in which different xylan fractions are removed from fiber cell wall during HTP, and we expect the information to be helpful in developing processes tailored for more effective conversion of cellulosic biomass into fermentable sugars. Springer-Verlag Berlin Heidelberg, 2015 Immunolocalization nationallicence Xylan nationallicence Hydrothermal pretreatment nationallicence Delignification nationallicence Enzymatic treatment nationallicence CML : Compound middle lamella nationallicence D+HTP : Hydrothermal pretreatment after delignification nationallicence HTP : Hydrothermal pretreatment nationallicence HTP+E : Hydrothermal pretreatment followed by enzymatic treatment nationallicence iS2 layer : Inner part of S2 layer nationallicence mS2 layer : Middle part of S2 layer nationallicence oS2 layer : Outer part of S2 layer nationallicence S layer : Secondary cell wall nationallicence S1 layer : Outer layer of secondary cell wall nationallicence S2 layer : Middle layer of secondary cell wall nationallicence TB : Toluidine blue nationallicence TEM : Transmission electron microscopy nationallicence Ma Jing Beijing Key Laboratory of Lignocellulosic Chemistry, Beijing Forestry University, 100083, Beijing, China aut Ji Zhe Beijing Key Laboratory of Lignocellulosic Chemistry, Beijing Forestry University, 100083, Beijing, China aut Chen Jia Shandong Key Laboratory of Pulp and Paper Engineering, Qilu University of Technology, 250353, Jinan, China aut Zhou Xia Beijing Key Laboratory of Lignocellulosic Chemistry, Beijing Forestry University, 100083, Beijing, China aut Kim Yoon Department of Wood Science and Engineering, Chonnam National University, 500757, Gwangju, South Korea aut Xu Feng Beijing Key Laboratory of Lignocellulosic Chemistry, Beijing Forestry University, 100083, Beijing, China aut Planta Springer Berlin Heidelberg 242/1(2015-07-01), 327-337 0032-0935 242:1<327 2015 242 425 https://doi.org/10.1007/s00425-015-2313-5 text/html Onlinezugriff via DOI BK010053 XK010053 XK010000 Metadata rights reserved Springer special CC-BY-NC licence nationallicence 1 research-article jats NATIONALLICENCE NATIONALLICENCE NL-springer NATIONALLICENCE 856 40 https://doi.org/10.1007/s00425-015-2313-5 text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Ma Jing Beijing Key Laboratory of Lignocellulosic Chemistry, Beijing Forestry University, 100083, Beijing, China aut NATIONALLICENCE 700 1- Ji Zhe Beijing Key Laboratory of Lignocellulosic Chemistry, Beijing Forestry University, 100083, Beijing, China aut NATIONALLICENCE 700 1- Chen Jia Shandong Key Laboratory of Pulp and Paper Engineering, Qilu University of Technology, 250353, Jinan, China aut NATIONALLICENCE 700 1- Zhou Xia Beijing Key Laboratory of Lignocellulosic Chemistry, Beijing Forestry University, 100083, Beijing, China aut NATIONALLICENCE 700 1- Kim Yoon Department of Wood Science and Engineering, Chonnam National University, 500757, Gwangju, South Korea aut NATIONALLICENCE 700 1- Xu Feng Beijing Key Laboratory of Lignocellulosic Chemistry, Beijing Forestry University, 100083, Beijing, China aut NATIONALLICENCE 773 0- Planta Springer Berlin Heidelberg 242/1(2015-07-01), 327-337 0032-0935 242:1<327 2015 242 425