Genetic engineering of grass cell wall polysaccharides for biorefining

Abstract

SummaryGrasses represent an abundant and widespread source of lignocellulosic biomass, which has yet to fulfil its potential as a feedstock for biorefining into renewable and sustainable biofuels and commodity chemicals. The inherent recalcitrance of lignocellulosic materials to deconstruction is the most crucial limitation for the commercial viability and economic feasibility of biomass biorefining. Over the last decade, the targeted genetic engineering of grasses has become more proficient, enabling rational approaches to modify lignocellulose with the aim of making it more amenable to bioconversion. In this review, we provide an overview of transgenic strategies and targets to tailor grass cell wall polysaccharides for biorefining applications. The bioengineering efforts and opportunities summarized here rely primarily on (A) reprogramming gene regulatory networks responsible for the biosynthesis of lignocellulose, (B) remodelling the chemical structure and substitution patterns of cell wall polysaccharides and (C) expressing lignocellulose degrading and/or modifying enzymes in planta. It is anticipated that outputs from the rational engineering of grass cell wall polysaccharides by such strategies could help in realizing an economically sustainable, grass‐derived lignocellulose processing industry.

Heteroexpression of Osa-miR319b improved switchgrass biomass yield and feedstock quality by repression of PvPCF5

“…Lignin is the major impediment to lignocellulose degrading [15,16]. To analyze whether the change in lignin content of OE-miR319 and MIM319 plants affected the enzymatic hydrolysis efficiency, we measured the enzymatic hydrolysis efficiency of cell wall residues (CWR) without pretreatment or after alkali pretreatment.…”

“…However, lignocellulose materials are blocked by lignin in the secondary cell walls, resulting in a poor saccharification efficiency [5]. In recent decades, regulating the expression of lignin biosynthesis genes [6][7][8][9][10] or transcription factors (TFs) that involved in secondary cell wall regulation, including members of Liu et al Biotechnol Biofuels (2020) 13:56 MYELOBLASTOSIS (MYB), NAM/ATAF/CUC (NAC), and APETALA2/Ethylene Responsive Factor (AP2/ERF) families [11][12][13][14], could efficiently alter lignin composition and structure and/or secondary cell wall remodeling, leading to enhanced sugar release efficiently [reviewed in 15,16]. However, those improvements were also accompanied with potential side effects such as stunted plant growth [11][12][13], sterile characteristics [12], or sensitivity to biotic and/or abiotic stresses [17,18].…”

Downregulation of p‐COUMAROYL ESTER 3‐HYDROXYLASE in rice leads to altered cell wall structures and improves biomass saccharification

“…In addition, grass biomass crops such as Erianthus, Miscanthus, switchgrass and bamboos, have attracted considerable attention as potent sources of lignocellulosic biomass due to their superior characteristics as biomass feedstocks: grass biomass typically shows much higher lignocellulose productivity as well as better processability than softwood and hardwood biomass (Somerville et al, 2010;Tye et al, 2016;Umezawa, 2018). To establish a cost-effective biorefinery system, molecular breeding approaches to further improve lignocellulose productivity and utilization characteristics in grass species are desired (Somerville et al, 2010;Cesarino et al, 2016;Bhatia et al, 2017). However, the majority of the genetic studies associated with the development and bioengineering of lignocellulose have traditionally targeted model eudicots such as Arabidopsis and poplar, and our knowledge of manipulating lignocellulose in monocotyledonous grass species remains limited (Hatfield et al, 2017).…”

Engineering of Bioenergy Crops: Dominant Genetic Approaches to Improve Polysaccharide Properties and Composition in Biomass

“…Research into the fundamental cell biology of plants and the organisms that degrade them has revealed the causes of biomass recalcitrance and a variety of approaches to reduce it. Significant improvements in biomass have been demonstrated by suppressing or eliminating the expression of various genes related to the biosynthesis of specific polysaccharides (Biswal et al, 2015Loqué et al, 2015;Kalluri et al, 2016;Wang et al, 2016;Willis et al, 2016;Bhatia et al, 2017;Donev et al, 2018;Li et al, 2019b). However, the usefulness of the same approaches in a range of bioenergy crops can be limited by their comparative genetic complexity.…”