Structure and enzymatic accessibility of leaf and stem from wheat straw before and after hydrothermal pretreatment

Biotechnology for Biofuels

Heng Zhang²  Lisbeth G Thygesen²  Kell Mortensen⁴  Zsófia Kádár¹  Jane Lindedam³  Henning Jørgensen⁵  Claus Felby² 

[1] Center for BioProcess Engineering, Department of Chemical and Biochemical Engineering, Technical University of Denmark, DTU, DK-2800, Kgs, Lyngby, Denmark

[2] Department of Geosciences and Natural Resource Management, Faculty of Sciences, University of Copenhagen, Rolighedsvej 23, DK-1958 Frederiksberg C, Denmark

[3] Department of Plant and Environmental Sciences, University of Copenhagen, Thorvaldsensvej 40, DK-1871 Frederiksberg C, Denmark

[4] Niels Bohr Institute, University of Copenhagen, Universitetsparken 5, D-03-3-06, DK-2100 Copenhagen Ø, Denmark

[5] Department of Chemical and Biochemical Engineering, Technical University of Denmark, 2800 Kgs, Lyngby, Denmark

关键词: glucan accessibility;    cellulose crystallinity;    water;    recalcitrance;    Wheat straw anatomical fractions;   

Others  :  792437
DOI  :  10.1186/1754-6834-7-74

 received in 2014-01-22, accepted in 2014-05-08,  发布年份 2014

【 摘 要 】

Background

Biomass recalcitrance is affected by a number of chemical, physical and biological factors. In this study we looked into the differences in recalcitrance between two major anatomical fractions of wheat straw biomass, leaf and stem. A set of twenty-one wheat cultivars was fractionated and illustrated the substantial variation in leaf-to-stem ratio between cultivars. The two fractions were compared in terms of chemical composition, enzymatic convertibility, cellulose crystallinity and glucan accessibility. The use of water as a probe for assessing glucan accessibility was explored using low field nuclear magnetic resonance and infrared spectroscopy in combination with hydrogen-deuterium exchange.

Results

Leaves were clearly more degradable by lignocellulolytic enzymes than stems, and it was demonstrated that xylose removal was more linked to glucose yield for stems than for leaves. Comparing the locations of water in leaf and stem by low field NMR and FT-IR revealed that the glucan hydroxyl groups in leaves were more accessible to water than glucan hydroxyl groups in stems. No difference in crystallinity between leaf and stem was observed using wide angle x-ray diffraction. Hydrothermal pretreatment increased the accessibility towards water in stems but not in leaves. The results in this study indicate a correlation between the accessibility of glucan to water and to enzymes.

Conclusions

Enzymatic degradability of wheat straw anatomical fractions can be indicated by the accessibility of the hydroxyl groups to water. This suggests that water may be used to assess glucan accessibility in biomass samples.

【 授权许可】

   
2014 Zhang et al.; licensee BioMed Central Ltd.

【 图 表 】

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