Linear and branched structures present in high-molar-mass fractions in holocelluloses prepared from chara, haircap moss, adiantum, ginkgo, Japanese cedar, and eucalyptus

Abstract

The land plants evolved from a salt-water algal ancestor, diversifying on land into fresh-water algae, mosses, ferns, gymnosperms, and finally the angiosperms that dominate land today. In this study, the structures of high-molar-mass fractions in holocelluloses prepared from chara (a freshwater alga), haircap moss, adiantum, ginkgo, Japanese cedar, and eucalyptus were investigated using size-exclusion chromatography with multi-angle laser-light scattering, ultraviolet, and refractive index detection (SEC/MALLS/UV/RI). 4% NaOH-extracted holocelluloses prepared from the above algal and land plants were dissolved in 8% (w/w) lithium chloride/N,N-dimethylacetamide and subjected to SEC/MALLS/UV/RI analysis. The neutral sugar compositions of the samples were also measured. The holocelluloses prepared from chara, haircap moss, and adiantum had the same crystalline microfibril structures (~ 3 nm in width) as those prepared from ginkgo, Japanese cedar, and eucalyptus. However, SEC/MALLS/UV/RI analysis gave different results among samples. Haircap moss, adiantum, Japanese cedar, and ginkgo had cellulose/glucomannan branched structures linked through degraded fragments of residual lignin or lignin-like phenolic compounds. In contrast, 4% NaOH-extracted chara holocellulose had no such branched structures, but contained the same linear structure as found in eucalyptus. The results obtained in this study, therefore, showed the possibility that land plant cellulose fibers, have branched structures with glucomannan in the HMM fractions, even though the cellulose fibers are prepared by repeated delignification and successive 4% NaOH extraction.