In muro deacetylation of xylan affects lignin properties and improves saccharification of aspen wood
Journal article, 2017

Background: Lignocellulose from fast growing hardwood species is a preferred source of polysaccharides for advanced biofuels and "green" chemicals. However, the extensive acetylation of hardwood xylan hinders lignocellulose saccharification by obstructing enzymatic xylan hydrolysis and causing inhibitory acetic acid concentrations during microbial sugar fermentation. To optimize lignocellulose for cost-effective saccharification and biofuel production, an acetyl xylan esterase AnAXE1 from Aspergillus niger was introduced into aspen and targeted to cell walls. Results: AnAXE1-expressing plants exhibited reduced xylan acetylation and grew normally. Without pretreatment, their lignocellulose yielded over 25% more glucose per unit mass of wood (dry weight) than wild-type plants. Glucose yields were less improved (+7%) after acid pretreatment, which hydrolyses xylan. The results indicate that AnAXE1 expression also reduced the molecular weight of xylan, and xylan-lignin complexes and/or lignin co-extracted with xylan, increased cellulose crystallinity, altered the lignin composition, reducing its syringyl to guaiacyl ratio, and increased lignin solubility in dioxane and hot water. Lignin-associated carbohydrates became enriched in xylose residues, indicating a higher content of xylo-oligosaccharides. Conclusions: This work revealed several changes in plant cell walls caused by deacetylation of xylan. We propose that deacetylated xylan is partially hydrolyzed in the cell walls, liberating xylo-oligosaccharides and their associated lignin oligomers from the cell wall network. Deacetylating xylan thus not only increases its susceptibility to hydrolytic enzymes during saccharification but also changes the cell wall architecture, increasing the extractability of lignin and xylan and facilitating saccharification.

Populus

Xylan

Wood

Plant-Cell Wall

Acetylation

Saccharification

Author

P. M. A. Pawar

Purdue University

Swedish University of Agricultural Sciences (SLU)

M. Derba-Maceluch

Swedish University of Agricultural Sciences (SLU)

Sun-Li Chong

Chalmers, Biology and Biological Engineering, Industrial Biotechnology

M. L. Gandla

Umeå University

S. S. Bashar

Swedish University of Agricultural Sciences (SLU)

T. Sparrman

Umeå University

P. Ahvenainen

University of Helsinki

M. Hedenstrom

Umeå University

M. Ozparpucu

Swiss Federal Laboratories for Materials Science and Technology (Empa)

Swiss Federal Institute of Technology in Zürich (ETH)

M. Ruggeberg

Swiss Federal Laboratories for Materials Science and Technology (Empa)

Swiss Federal Institute of Technology in Zürich (ETH)

R. Serimaa

University of Helsinki

M. Lawoko

Royal Institute of Technology (KTH)

M. Tenkanen

University of Helsinki

L. J. Jonsson

Umeå University

E. J. Mellerowicz

Swedish University of Agricultural Sciences (SLU)

Biotechnology for Biofuels

17546834 (ISSN) 1754-6834 (eISSN)

Vol. 10 1 Art nr 98- 98

Subject Categories

Industrial Biotechnology

DOI

10.1186/s13068-017-0782-4

More information

Latest update

1/20/2021