In muro deacetylation of xylan affects lignin properties and improves saccharification of aspen wood
Artikel i vetenskaplig tidskrift, 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.

Xylan

Plant-Cell Wall

Saccharification

Acetylation

Populus

Wood

Författare

P. M. A. Pawar

Purdue University

Sveriges lantbruksuniversitet (SLU)

M. Derba-Maceluch

Sveriges lantbruksuniversitet (SLU)

Sun-Li Chong

Chalmers, Biologi och bioteknik, Industriell bioteknik

M. L. Gandla

Umeå universitet

S. S. Bashar

Sveriges lantbruksuniversitet (SLU)

T. Sparrman

Umeå universitet

P. Ahvenainen

Helsingin Yliopisto

M. Hedenstrom

Umeå universitet

M. Ozparpucu

Eidgenössische Technische Hochschule Zürich (ETH)

Forschungsinstitution fur Materialwissenschaften Und Technologie Eth-Bereichs

M. Ruggeberg

Eidgenössische Technische Hochschule Zürich (ETH)

Forschungsinstitution fur Materialwissenschaften Und Technologie Eth-Bereichs

R. Serimaa

Helsingin Yliopisto

M. Lawoko

Kungliga Tekniska Högskolan (KTH)

M. Tenkanen

Helsingin Yliopisto

L. J. Jonsson

Umeå universitet

E. J. Mellerowicz

Sveriges lantbruksuniversitet (SLU)

Biotechnology for Biofuels

1754-6834 (eISSN)

Vol. 10 1 Art nr 98- 98

Ämneskategorier

Industriell bioteknik

DOI

10.1186/s13068-017-0782-4