A Comparative Investigation of the Ultrastructure of Steam Exploded Wood With Light, Scanning and Transmission Electron Microscopy

Abstract

KeywordsWood anatomy Steam explosion treatment Topochemistry of lignin redistribution Staining Drying SummaryThe changes in anatomy, Ultrastructure and topochemistry of aspen wood degraded by steam explosion treatment were investigated by light, scanning and transmission electron microscopy. Light microscopy provided an overview of the general changes in wood architecture and revealed the opposite roles of the vessels and ray cells. Scanning electron micrographs showed the fibrillar architecture of the fibre surface. Transmission electron micrographs showed that in addition to lignin redistribution on both the inner and outer surfaces of the cell wall, this also occurs inside the cell wall itself Lamellar deposition of lignin within the secondary cell wall and free fibrils in the extract were also observed. Special studies were undertaken to ensure that the best method was used to dry the wet samples for examination in the scanning electron microscope. Observation on all the three different microscopical levels is probably the best possible approach to this ultrastructural problem. * 4.42Holzforschung / Vol. 49 / 1995 / No. 2

Effect of initial moisture content and chip size on the bioconversion efficiency of softwood lignocellulosics

“…Thus, the primary reason for the improved efficacy of lignin removal is likely due to decreased condensation of the residual lignin. As lignin condenses it has been shown to restrict the swelling of the fibers, and therefore increase the difficulty of delignification chemicals to interact with the fibrous matrix by blocking pores and cracks within the cell wall (Schwald et al, 1989;Shevchenko et al, 1999;Toussaint et al, 1991;Kallavus and Gravitis, 1995). Additionally, the melting and condensation of lignin lowers the reactivity of the lignin, generating a residual product that has limited reactivity with delignification chemicals (Hemmingson, 1987).…”

Lignin Structural Alterations in Thermochemical Pretreatments with Limited Delignification

“…In addition to chemical alternations in its structure, lignin is also found to translocate and redistribute in biomass under acidic pretreatment conditions such as DAP, HWP, and SEP, leading to the formation of lignin droplets or agglomerates with various morphologies [62,[105][106][107][108][109][110][111]. Selig et al [105] documented the presence of spherical lignin droplets on the surface of maize stem after dilute acid pretreatment.…”

“…The lignin redistribution together with hemicellulose removal during steam explosion led to increased porosity of microfibrillar web which contributed to the enhanced digestibility of steam pretreated wood. Using transmission electron microscope, Kallavus and Gravitis [110] observed lignin redistribution on both the inner and outer surfaces of cell walls as well as inside the cell wall itself after steam explosion treatment of aspen wood.…”

Paulownia as a raw material for the production of pulp by soda–anthraquinone cooking with or without previous autohydrolysis

“…Overall, these results can be ascribed to substantial destructuring of fibres in the raw material by the autohydrolysis treatment, which essentially affects the operating time or temperature to be used in the subsequent, delignification step to facilitate access of the reagents to the cellulose matrix. 29,30 For comparison, Table 5 shows results with and without autohydrolysis (Tables 2 and 3), and those of other authors for cellulose pulp and paper obtained from diverse Paulownia varieties. The four right-most columns correspond to the pulping of RM and SF for the trihybrid clone studied here.…”