Extraction, recovery, and characterization of hardwood and grass hemicelluloses for integration into biorefining processes

Ryan J. Stoklosa, David B. Hodge

    Research output: Research - peer-reviewArticle

    • 17 Citations

    Abstract

    For this work, four hardwoods (silver birch, sugar maple, a hybrid poplar, and a hybrid aspen) and one cultivar of switchgrass were treated with increasing levels of NaOH. The recovered cell wall biopolymers were characterized based on total extraction, precipitation using ethanol or acidification, xylan content, and molar mass of the recovered precipitates. The extractability of cell wall polymers was clearly shown to be a function of the biomass type with more than 50% of the cell walls of switchgrass solubilized by alkali while only up to 20% of the maple was solubilized under comparable conditions. Precipitation with ethanol resulted in high recovery yields of hemicelluloses from the original biomass for silver birch and switchgrass, and most notably, the birch precipitates contained double the hemicellulose content of the precipitates from other feedstock alkali extracts (80% versus 30-50%). The molar masses of the recovered hemicellulosic polysaccharides were characterized using size exclusion chromatography (SEC) and an assay to quantify polysaccharide reducing ends. SEC analysis showed that the biopolymers exhibited a strong tendency to self-associate during elution and that this aggregation could be eliminated through sonication. The reducing end method showed an increase in the number-average degree of polymerization toward an asymptotic maximum with increasing extraction pH, and this value was significantly increased by bleaching the precipitate to remove interference by nonpolysaccharides.

    LanguageEnglish (US)
    Pages11045-11053
    Number of pages9
    JournalIndustrial and Engineering Chemistry Research
    Volume51
    Issue number34
    DOIs
    StatePublished - Aug 29 2012

    Profile

    Hardwoods
    Precipitates
    Recovery
    hemicellulose
    Cells
    Biopolymers
    Size exclusion chromatography
    Molar mass
    Alkalies
    Silver
    Polysaccharides
    Biomass
    Ethanol
    Xylans
    Sonication
    Acidification
    Bleaching
    Sugars
    Feedstocks
    Assays

    ASJC Scopus subject areas

    • Chemical Engineering(all)
    • Chemistry(all)
    • Industrial and Manufacturing Engineering

    Cite this

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    abstract = "For this work, four hardwoods (silver birch, sugar maple, a hybrid poplar, and a hybrid aspen) and one cultivar of switchgrass were treated with increasing levels of NaOH. The recovered cell wall biopolymers were characterized based on total extraction, precipitation using ethanol or acidification, xylan content, and molar mass of the recovered precipitates. The extractability of cell wall polymers was clearly shown to be a function of the biomass type with more than 50% of the cell walls of switchgrass solubilized by alkali while only up to 20% of the maple was solubilized under comparable conditions. Precipitation with ethanol resulted in high recovery yields of hemicelluloses from the original biomass for silver birch and switchgrass, and most notably, the birch precipitates contained double the hemicellulose content of the precipitates from other feedstock alkali extracts (80% versus 30-50%). The molar masses of the recovered hemicellulosic polysaccharides were characterized using size exclusion chromatography (SEC) and an assay to quantify polysaccharide reducing ends. SEC analysis showed that the biopolymers exhibited a strong tendency to self-associate during elution and that this aggregation could be eliminated through sonication. The reducing end method showed an increase in the number-average degree of polymerization toward an asymptotic maximum with increasing extraction pH, and this value was significantly increased by bleaching the precipitate to remove interference by nonpolysaccharides.",
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