It is widely recognized that the production of biofuels and bioproducts from lignocellulosic biomass has the potential to address societal needs, such as those for renewable energy and chemicals. Switchgrass has been identified as a promising biomass feedstock for energy production due to its high yield and environmental benefits. However, as with all lignocellulosic biomass, there is tremendous variability associated with the switchgrass cell wall. This inherent variability induces problems in the development of downstream processes and has been identified by the US DOE as a barrier to the implementation of commercial-scale integrated biorefineries. It is of particular interest to understand and effectively control the variability of lignin – a heterogeneous, aromatic biopolymer which acts as the glue keeping the cell wall intact. To quantify the variability of lignin in switchgrass, we analyzed over 100 natural variant switchgrass genotypes from a genome-wide association study (GWAS) population. Nuclear magnetic resonance (NMR) was utilized to quantify lignin composition, including relative abundance of syringyl, guaiacyl and <i>p</i>-hydroxyphenol units, as well as interunit linkages such as β-O-4, β-5, and β-β. Lignin compositional traits were then analyzed in a GWAS to identify candidate genes associated with each lignin phenotype. Other physical properties of lignin, such as molecular weight, were also measured to quantify variability. Finally, biomass samples were analyzed by FTIR to quantify other cell wall properties such as cellulose crystallinity. This detailed analysis of lignin structure across a GWAS population lays the groundwork for quantifying lignin variability in switchgrass and provides insights into the genetic control of cell wall features.

Elucidating the structure and variability of lignin and the underlying genetic factors in a diverse switchgrass population

ACS Spring Meeting 2021

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