Stacking of a low-lignin trait with an increased guaiacyl and 5-hydroxyguaiacyl unit trait leads to additive and synergistic effects on saccharification efficiency in Arabidopsis thaliana

Rebecca Van Acker,Wout Boerjan,Lisa Sundin,Barbara De Meester,Lisanne de Vries,Ruben Vanholme

doi:10.1186/s13068-018-1257-y

Rebecca Van Acker, Wout Boerjan + Show 4 more

Open Access

https://doi.org/10.1186/s13068-018-1257-y

Copy DOI

Abstract

BackgroundLignocellulosic biomass, such as wood and straw, is an interesting feedstock for the production of fermentable sugars. However, mainly due to the presence of lignin, this type of biomass is recalcitrant to saccharification. In Arabidopsis, lignocellulosic biomass with a lower lignin content or with lignin with an increased fraction of guaiacyl (G) and 5-hydroxyguaiacyl (5H) units shows an increased saccharification efficiency. Here, we stacked these two traits and studied the effect on the saccharification efficiency and biomass yield, by combining either transaldolase (tra2), cinnamate 4-hydroxylase (c4h-3), or 4-coumarate:CoA ligase (4cl1-1) with caffeic acid O-methyltransferase (comt-1 or comt-4) mutants.ResultsThe three double mutants (tra2 comt-1, c4h-3 comt-4, and 4cl1-1 comt-4) had a decreased lignin amount and an increase in G and 5H units in the lignin polymer compared to wild-type (WT) plants. The tra2 comt-1 double mutant had a better saccharification efficiency compared to the parental lines when an acid or alkaline pretreatment was used. For the double mutants, c4h-3 comt-4 and 4cl1-1 comt-4, the saccharification efficiency was significantly higher compared to WT and its parental lines, independent of the pretreatment used. When no pretreatment was used, the saccharification efficiency increased even synergistically for these mutants.ConclusionOur results show that saccharification efficiency can be improved by combining two different mutant lignin traits, leading to plants with an even higher saccharification efficiency, without having a yield reduction of the primary inflorescence stem. This approach can help improve saccharification efficiency in bio-energy crops.

Highlights

Lignocellulosic biomass, such as wood and straw, is an interesting feedstock for the production of fermentable sugars
Stacking reduced lignin content with G‐ and 5H‐rich lignin does not result in a biomass yield penalty In an attempt to stack a low-lignin trait with an increased incorporation of G and 5H units in Arabidopsis, we crossed either tra2, c4h-3, or 4cl1-1 with either comt-1 or comt-4
The three double mutants all had a reduced lignin amount, a lower S/G ratio, and an increased amount of 5H units, which means that the lignin traits of both parental lines were successfully combined in the double mutants

Summary

Introduction

Lignocellulosic biomass, such as wood and straw, is an interesting feedstock for the production of fermentable sugars. To overcome the recalcitrance of the plant cell wall and increase the saccharification efficiency, strategies aiming at lowering the amount or changing the composition of lignin have been tested in various plant species with some degree of success [8,9,10, 12,13,14,15,16,17]. These alterations are often accompanied by a biomass penalty, hindering their potential for applications. There is a need to optimize the balance between lignin engineering, yield penalty, and saccharification efficiency

Methods

Results

Discussion

Conclusion