Overcoming Biomass Recalcitrance by Combining Genetically Modified Switchgrass and Cellulose Solvent-Based Lignocellulose Pretreatment

Noppadon Sathitsuksanoh,Bingyu Zhao,Bin Xu,Y.-H Percival Zhang,Tianzhen Zhang

doi:10.1371/journal.pone.0073523

Noppadon Sathitsuksanoh, Bingyu Zhao + Show 3 more

Open Access

https://doi.org/10.1371/journal.pone.0073523

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Abstract

Decreasing lignin content of plant biomass by genetic engineering is believed to mitigate biomass recalcitrance and improve saccharification efficiency of plant biomass. In this study, we compared two different pretreatment methods (i.e., dilute acid and cellulose solvent) on transgenic plant biomass samples having different lignin contents and investigated biomass saccharification efficiency. Without pretreatment, no correlation was observed between lignin contents of plant biomass and saccharification efficiency. After dilute acid pretreatment, a strong negative correlation between lignin content of plant samples and overall glucose release was observed, wherein the highest overall enzymatic glucan digestibility was 70% for the low-lignin sample. After cellulose solvent- and organic solvent-based lignocellulose fractionation pretreatment, there was no strong correlation between lignin contents and high saccharification efficiencies obtained (i.e., 80–90%). These results suggest that the importance of decreasing lignin content in plant biomass to saccharification was largely dependent on pretreatment choice and conditions.

Highlights

Biomass recalcitrance to saccharification is one of the major obstacles to cost-efficient production of biofuels and value-added biochemicals from lignocellulose
Impact of Pv4CL1 suppression on lignin content of transgenic plants was initially screened by autofluorescence and phloroglucinol staining of transverse stem sections [11,17]
The lignin contents of nine selected T1 transgenic plants and pooled wild type samples were further measured according to the standard NREL protocol

Summary

Introduction

Biomass recalcitrance to saccharification is one of the major obstacles to cost-efficient production of biofuels and value-added biochemicals from lignocellulose. Down-regulation of lignin biosynthesis enzymes in alfalfa decreased plant lignin content, resulting in improved enzymatic saccharification efficiency with dilute sulfuric acid pretreated biomass [9]. Lignin content of wild type and transgenic switchgrass lines (C). We compared the saccharification efficiencies of DA pretreatment and COSLIF on multiple transgenic plant lines, whose lignin contents were regulated by controlling the expression of a lignin synthesis gene 4-coumarate: COA ligase (4cl) [11].

Results

Conclusion