標準セルロース粉末と木材のミクロフィブリルの構造

Abstract

X線回折法より計算されるセルロース・ミセル幅と, 電子顕微鏡により求められるそのミクロフィブリル幅について, 標準セルロース粉末 (Whatman セルロース) とアカマツとを比較すると, 前者の方がミセル幅・ミクロフィブリル幅ともに大きく, これはミクロフィブリル自体の結晶芯の差異によるものと推察される。また, アカマツのホロセルロースでは, ミクロフィブリルに折れ曲がり部分があることから, 高結晶性が推定される。さらに同試料の加水分解およびセルラーゼ処理によるミクロフィブリルの幅の変化から, ミクロフィブリル結晶芯のまわりのパラクリスタリン領域は加水分解の条件により, 結晶化したり, 取り除かれたりすると考えられる。

Cellulose microfibrils of Standard Cellulose Powder (Whatman cellulose) and wood (Akamatsu, Pinus densiflora SIEB. et ZUCC.) were studied by X-ray diffraction and electron microscopy. The powder of each material was pressed into a tablet for the measurement of micelle width which was calculated from X-ray line broadening by the Scherrer equation (Fig. 1). The materials were also mechanically disintegrated in a homogenizer and they were mixed with negative staining solution (4% uranyl acetate) (Figs. 2, 3, 4). The widths of microfibrils were measured directly from the electron micrographs. Both the widths measured by X-ray diffraction and electron microscope from Whatman cellulose were greater than those from Akamatsu (Table 1), and it has been shown that the difference of the widths originated in the crystalline core of the microfibrils. The kinkings of microfibrils in Akamatsu holocellulose were observed (Fig. 3) to indicate that the microfibrils may be highly crystalline. The shift of microfibril width by treatment with hydrochloric acid and cellulase (Trichoderma viride) suggests that some portion of the paracrystalline regions surrounding microfibril cores is either crystallized or dissolved away, depending on the condition of the treatment (Figs. 8, 9, 10, 11).