Chemical characterization of bark lignins

2023 Fiscal Year Final Research Report

• Project/Area Number: 20K06173
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Review Section: Basic Section 40020:Wood science-related
• Research Institution: The University of Tokyo (2022-2023); Forest Research and Management Organization (2020-2021)
• Principal Investigator: Akiyama Takuya 東京大学, 大学院農学生命科学研究科(農学部), 准教授 (50553723)
• Project Period (FY): 2020-04-01 – 2024-03-31
• Keywords: 内樹皮 / 外樹皮 / 単離リグニン / ニトロベンゼン酸化 / NMR / MWL

Outline of Final Research Achievements

Lignin in the inner and outer bark of softwood (Japanese cedar) was chemically characterized by comparison with its xylem lignin. The ratios (mole ratios) of non-condensed/β-5/biphenyl-type products obtained by the chemical degradation method showed almost no significant differences among the xylem, inner bark, and outer bark samples. Lignin (MWL) was isolated from the xylem and inner bark, and their 1H-NMR and 1H,13C two-dimensional NMR (HSQC) spectra were compared. No significant differences were observed between the xylem and inner bark, and peaks assigned to β-O-4, phenylcoumaran, resinol, and dibenzodioxocin structures were observed in the inner bark lignin as in the xylem. Throughout this study, the only significant difference between the lignin of the xylem and inner bark was in lignin content, with the inner bark having a Klason lignin content of 21%, less than two-thirds that of the sapwood.

Free Research Field

木質化学

Academic Significance and Societal Importance of the Research Achievements

樹皮はバイオマス総合利用の観点から重要な木質資源であるが、その構成成分には未解明な部分が多く、木部と比べ化学的特徴の理解が遅れている。国内の針葉樹を代表するスギに関して、木部と樹皮を構成するリグニンは似ており、その高分子を構成する各部分構造の割合はほぼ同じであることが明らかになった。この研究成果は、細胞壁形成時における木化機構の理解へ向けた新たな基礎的知見として学術的意義があり、また、社会的意義としてリグニン利用技術を設計するための基盤的知見を得ることができた。