Abstract:BackgroundHeterogeneity within herbaceous biomass can present important challenges for processing feedstocks to cellulosic biofuels. Alterations to cell wall composition and organization during plant growth represent major contributions to heterogeneity within a single species or cultivar. To address this challenge, the focus of this study was to characterize the relationship between composition and properties of the plant cell wall and cell wall response to deconstruction by NaOH pretreatment and enzymatic hy… Show more
“…Despite this, we cannot presume that lignin is the only recalcitrance-enhancing agent in stem biomass. Indeed, in switchgrass, although lignin content is generally negatively correlated with saccharification, it is not the sole contributor to recalcitrance across diverse anatomical features [87]. Fig.…”
Background
Lignocellulosic biomass from dedicated energy crops such as
Miscanthus
spp. is an important tool to combat anthropogenic climate change. However, we still do not exactly understand the sources of cell wall recalcitrance to deconstruction, which hinders the efficient biorefining of plant biomass into biofuels and bioproducts.
Results
We combined detailed phenotyping, correlation studies and discriminant analyses, to identify key significantly distinct variables between miscanthus organs, genotypes and most importantly, between saccharification performances. Furthermore, for the first time in an energy crop, normalised total quantification of specific cell wall glycan epitopes is reported and correlated with saccharification.
Conclusions
In stems, lignin has the greatest impact on recalcitrance. However, in leaves, matrix glycans and their decorations have determinant effects, highlighting the importance of biomass fine structures, in addition to more commonly described cell wall compositional features. The results of our interrogation of the miscanthus cell wall promote the concept that desirable cell wall traits for increased biomass quality are highly dependent on the target biorefining products. Thus, for the development of biorefining ideotypes, instead of a generalist miscanthus variety, more realistic and valuable approaches may come from defining a collection of specialised cultivars, adapted to specific conditions and purposes.
Electronic supplementary material
The online version of this article (10.1186/s13068-019-1426-7) contains supplementary material, which is available to authorized users.
“…Despite this, we cannot presume that lignin is the only recalcitrance-enhancing agent in stem biomass. Indeed, in switchgrass, although lignin content is generally negatively correlated with saccharification, it is not the sole contributor to recalcitrance across diverse anatomical features [87]. Fig.…”
Background
Lignocellulosic biomass from dedicated energy crops such as
Miscanthus
spp. is an important tool to combat anthropogenic climate change. However, we still do not exactly understand the sources of cell wall recalcitrance to deconstruction, which hinders the efficient biorefining of plant biomass into biofuels and bioproducts.
Results
We combined detailed phenotyping, correlation studies and discriminant analyses, to identify key significantly distinct variables between miscanthus organs, genotypes and most importantly, between saccharification performances. Furthermore, for the first time in an energy crop, normalised total quantification of specific cell wall glycan epitopes is reported and correlated with saccharification.
Conclusions
In stems, lignin has the greatest impact on recalcitrance. However, in leaves, matrix glycans and their decorations have determinant effects, highlighting the importance of biomass fine structures, in addition to more commonly described cell wall compositional features. The results of our interrogation of the miscanthus cell wall promote the concept that desirable cell wall traits for increased biomass quality are highly dependent on the target biorefining products. Thus, for the development of biorefining ideotypes, instead of a generalist miscanthus variety, more realistic and valuable approaches may come from defining a collection of specialised cultivars, adapted to specific conditions and purposes.
Electronic supplementary material
The online version of this article (10.1186/s13068-019-1426-7) contains supplementary material, which is available to authorized users.
“…Together with the polysaccharides cellulose and hemicellulose, lignin is one of the principal structural polymers of the cell walls of terrestrial plants and can comprise up to 30% of the mass of a plant on a dry basis. The composition and properties of the lignin in a plant prior to processing are a complex function of its source derived from plant taxonomy and genotype, development stage, environment, and tissue type [25]. Gymnosperm lignins are comprised primarily of monomers derived from coniferyl alcohol, corresponding to the guaiacyl or “G” monomer upon incorporation into the lignin polymer, while angiosperm lignins are comprised primarily of monomers derived from coniferyl and sinapyl alcohols (syringyl or “S” monomer) (Figure 1) [26].…”
Section: Impact Of Source Processing History and Functionalizatimentioning
Polyurethane chemistry can yield diverse sets of polymeric materials exhibiting a wide range of properties for various applications and market segments. Utilizing lignin as a polyol presents an opportunity to incorporate a currently underutilized renewable aromatic polymer into these products. In this work, we will review the current state of technology for utilizing lignin as a polyol replacement in different polyurethane products. This will include a discussion of lignin structure, diversity, and modification during chemical pulping and cellulosic biofuels processes, approaches for lignin extraction, recovery, fractionation, and modification/functionalization. We will discuss the potential of incorporation of lignins into polyurethane products that include rigid and flexible foams, adhesives, coatings, and elastomers. Finally, we will discuss challenges in incorporating lignin in polyurethane formulations, potential solutions and approaches that have been taken to resolve those issues.
“…Consistently, expression of secondary cell wall-related genes has been shown to be higher in stems (Zhao and Bartley, 2014;Mazarei et al, 2018;Rao et al, 2019). Noteworthy, other than inflorescence, the tissues of high PvFPGS1 expression in switchgrass are all significantly lignified (Crowe et al, 2017).…”
Switchgrass (Panicum virgatum L.) is a lignocellulosic perennial grass with great potential in bioenergy field. Lignocellulosic bioenergy crops are mostly resistant to cell wall deconstruction, and therefore yield suboptimal levels of biofuel. The one-carbon pathway (also known as C1 metabolism) is critical for polymer methylation, including that of lignin and hemicelluloses in cell walls. Folylpolyglutamate synthetase (FPGS) catalyzes a biochemical reaction that leads to the formation of folylpolyglutamate, an important cofactor for many enzymes in the C1 pathway. In this study, the putatively novel switchgrass PvFPGS1 gene was identified and its functional role in cell wall composition and biofuel production was examined by RNAi knockdown analysis. The PvFPGS1-downregulated plants were analyzed in the field over three growing seasons. Transgenic plants with the highest reduction in PvFPGS1 expression grew slower and produced lower end-of-season biomass. Transgenic plants with low-to-moderate reduction in PvFPGS1 transcript levels produced equivalent biomass as controls. There were no significant differences observed for lignin content and syringyl/guaiacyl lignin monomer ratio in the low-to-moderately reduced PvFPGS1 transgenic lines compared with the controls. Similarly, sugar release efficiency was also not significantly different in these transgenic lines compared with the control lines. However, transgenic plants produced up to 18% more ethanol while maintaining congruent growth and biomass as non-transgenic controls. Severity of rust disease among transgenic and control lines were not different during the time course of the field experiments. Altogether, the unchanged lignin content and composition in the low-to-moderate PvFPGS1-downregulated lines may suggest that partial downregulation of PvFPGS1 expression did not impact lignin biosynthesis in switchgrass. In conclusion, the manipulation of PvFPGS1 expression in bioenergy crops may be useful to increase biofuel potential with no growth penalty or increased susceptibility to rust in feedstock.
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