Comparison of changes in cellulose ultrastructure during different pretreatments of poplar
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One commonly cited factor that contributes to the recalcitrance of biomass is cellulose crystallinity. The present study aims to establish the effect of several pretreatment technologies on cellulose crystallinity, crystalline allomorph distribution, and cellulose ultrastructure. The observed changes in the cellulose ultrastructure of poplar were also related to changes in enzymatic hydrolysis, a measure of biomass recalcitrance. Hot-water, organo-solv, lime, lime-oxidant, dilute acid, and dilute acid-oxidant pretreatments were compared in terms of changes in enzymatic sugar release and then changes in cellulose ultrastructure measured by 13C cross polarization magic angle spinning nuclear magnetic resonance and wide-angle X-ray diffraction. Pretreatment severity and relative chemical depolymerization/degradation were assessed through compositional analysis and high-performance anion-exchange chromatography with pulsed amperometric detection. Results showed minimal cellulose ultrastructural changes occurred due to lime and lime-oxidant pretreatments, which at short residence time displayed relatively high enzymatic glucose yield. Hot water pretreatment moderately changed cellulose crystallinity and crystalline allomorph distribution, yet produced the lowest enzymatic glucose yield. Dilute acid and dilute acid-oxidant pretreatments resulted in the largest increase in cellulose crystallinity, para-crystalline, and cellulose-Iβ allomorph content as well as the largest increase in cellulose microfibril or crystallite size. Perhaps related, compositional analysis and Klason lignin contents for samples that underwent dilute acid and dilute acid-oxidant pretreatments indicated the most significant polysaccharide depolymerization/degradation also ensued. Organo-solv pretreatment generated the highest glucose yield, which was accompanied by the most significant increase in cellulose microfibril or crystallite size and decrease in relatively lignin contents. Hot-water, dilute acid, dilute acid-oxidant, and organo-solv pretreatments all showed evidence of cellulose microfibril coalescence.
KeywordsBiomass pretreatment Cellulose Ultrastructure Crystallinity Enzymatic hydrolysis
Hybrid poplar samples were obtained through a collaborative agreement with the Bioenergy Science Center (BESC) located at the Oak Ridge National Laboratory, Oak Ridge, Tennessee. This research is funded by the Genomic Science Program, Office of Biological and Environmental Research, U. S. Department of Energy, under FWP ERKP752 and US Department of Energy sponsored BioEnergy Science Center (BESC). Oak Ridge National Laboratory’s Center for Structural Molecular Biology (CSMB) is supported by the Office of Biological and Environmental Research (FWP ERKP291). A portion of this research was also conducted at the Center for Nanophase Materials Sciences, which is sponsored at Oak Ridge National Laboratory by the Scientific User Facilities Division, Office of Basic Energy Sciences, U. S. Department of Energy. Q. S. is grateful for the financial support from the Paper Science & Engineering (PSE) fellowship program at Institute of Paper Science & Technology (IPST) at Georgia Institute of Technology.
- Arantes V, Saddler JN (2010) Access to cellulose limits the efficiency of enzymatic hydrolysis: the role of amorphogenesis. Biotechnol Biofuels 3Google Scholar
- Boisset C, Fraschini C, Schulein M, Henrissat B, Chanzy H (2000) Imaging the enzymatic digestion of bacterial cellulose ribbons reveals the endo character of the cellobiohydrolase Cel6A from Humicola insolens and its mode of synergy with cellobiohydrolase Cel7A. Appl Environ Microbiol 66:1444–1452CrossRefGoogle Scholar
- Brunner AM, Busov VB, Strauss SH (2004) Poplar genome sequence: functional genomics in an ecologically dominant plant species. Trends Plant Sci 9:49–56Google Scholar
- Cullity BD, Stock SR (2001) Elements of X-ray diffraction, 3rd edn. Prentice Hall, Upper Saddle RiverGoogle Scholar
- Foston M, Hubbell CA, Samuel R, Jung S, Fan H, Ding SY, Zeng YN, Jawdy S, Davis M, Sykes R, Gjersing E, Tuskan GA, Kalluri U, Ragauskas AJ (2011) Chemical, ultrastructural and supramolecular analysis of tension wood in Populus tremula x alba as a model substrate for reduced recalcitrance. Energy Environ Sci 4:4962–4971CrossRefGoogle Scholar
- Ioelovich M, Leykin A, Figovsky O (2010) Study of cellulose paracrystallinity. BioResources 5:1393–1407Google Scholar
- Klug HP, Alexander LE (1974) X-ray diffraction procedures for polycrystalline and amorphous materials, 2nd edn. Wiley, New YorkGoogle Scholar